Arquivo da tag: Geologia

How can I become a fossil? (BBC Future)

How to be fossilized (Credit: Getty) Less than one-10th of 1% of all species that have ever lived became fossils. But from skipping a coffin to avoiding Iran, there are ways to up your chances of lasting forever.

By John Pickrell

15 February 2018

Every fossil is a small miracle. As author Bill Bryson notes in his book A Short History of Nearly Everything, only an estimated one bone in a billion gets fossilised. By that calculation the entire fossil legacy of the 320-odd million people alive in the US today will equate to approximately 60 bones – or a little over a quarter of a human skeleton.

But that’s just the chance of getting fossilised in the first place. Assuming this handful of bones could be buried anywhere in the US’s 9.8 million sq km (3.8 million square miles), then the chances of anyone finding these bones in the future are almost non-existent.

Fossilisation is so unlikely that scientists estimate that less one-tenth of 1% of all the animal species that have ever lived have become fossils. Far fewer of them have been found.

As humans, we have a couple of things going for us: we have hard skeletons and we’re relatively large. So we’re much more likely to make it than a jellyfish or a worm. There are things, however, you can do to increase your chances of success.

Taphonomy is the study of burial, decay and preservation – the entire process of what happens after an organism dies and eventually becomes a fossil. To answer the question of how to become a fossil, BBC Future spoke with some of the world’s top taphonomists.

1. Get buried, and quickly

“It’s really a question of maintaining a good condition of the body after death – long enough to be buried under sediment and then altered physically and chemically deep underground to become a fossil,” says Sue Beardmore, a taphonomist and collections assistant at the Oxford University Museum of Natural History.

“To be preserved for millions of years, you must also survive the first hours, days, seasons, decades, centuries, and thousands of years,” adds Susan Kidwell, a professor at the University of Chicago. “That is, you must survive the initial transition from the ‘taphonomically active zone’… to a zone of permanent burial, where your remains are unlikely to be exhumed.”

There are almost endless ways that fossilisation can fail. Many of these happen at, or down to 20-50cm below, the soil or seafloor surface. You don’t want your remains to be eaten and scattered by scavengers, for example, or exposed to the elements for too long. And you don’t want them to be bored into or shifted around by burrowing animals.

The sand and mud deposits of Canada’s Badlands quickly buried bones The sand and mud deposits of Canada’s Badlands quickly buried bones, making the area one of the world’s richest hunting grounds for dinosaur fossils (Credit: Getty)

When it comes to rapid burial, sometimes natural disasters can help – such as floods that dump huge amounts of sediment or volcanic eruptions that smother things in mud and ash. “One theory for the occurrence of dinosaur bone beds is firstly drought conditions, that killed the dinosaurs, followed by floods that moved the sediments to bury them,” Beardmore says.

Of course, the fact that human bodies are typically buried six feet under (unless cremated) gives you another leg up here. But that isn’t enough on its own.

2. Find some water

Obviously the first step is dying, but you can’t die just anywhere. Picking the perfect environment is key. Water is one important thing to consider. If you die in a dry environment, once you’ve been picked over by scavengers, your bones will probably weather away at the surface. Instead, most experts agree you need to get swiftly smothered in sand, mud and sediments – and the best places for that are lakes, floodplains and rivers, or the bottom of the sea.

“The palaeoenvironments that we often see the best fossils come out of are lake and river systems,” says Caitlin Syme, a taphonomist at the University of Queensland in Brisbane, Australia. The important thing is the rate at which fresh sediments are burying things. She recommends rivers flowing from mountains which cause erosion and therefore carry a lot of sediment. Another option is a coastal delta or floodplain, where river sediment is rapidly dumped as the water heads out to sea.

Ideally, you also want an ‘anoxic’ environment: one very low in oxygen, where animals and microorganisms that would digest and disturb your remains can’t survive.

Kidwell recommends avoiding about 50cm below the seafloor, “the maximum burrowing depth of shrimp, crabs and worms that might irrigate the sediments with oxygenated water”, which would promote decomposition and stir up the body.

“You want to end up quickly after death in a spot that is relatively low elevation, so that it is a sink for sediment, and preferably with standing water – a pond, lake, estuary or ocean – so that anoxic conditions might develop,” she says.

A 150 million year old archaeopteryx (Credit: Getty)

Choose the right conditions and you, too, could be preserved for as long as this 150 million year old archaeopteryx (Credit: Getty)

In rare cases, fossils created in these kind of still, anoxic conditions preserve their soft tissues like skin, feathers and internal organs. Examples include the many exquisite feathered dinosaurs from China or the Bavarian quarries that produced the fossils of the earliest bird, archaeopteryx.

Once your fossil gets below the biologically active surface layer, then it’s stable and will continue to be buried more deeply as further sediments accumulate, Kidwell says. “The risk for destruction then shifts to a completely different geological timescale, namely that of tectonism.”

The question, then, is how long before the sediments encasing the corpse are turned to more permanent stone… and are lifted by geological activity to a height where erosion can expose the remains.

3. Skip the coffin

Now we come to the thorny technicality of what a fossil actually is – and what kind of fossil you want your body to be.

Very generally, anything up to around 50,000 years old is what’s known as a ‘subfossil’. These are largely still made up of the original tissues of the organism. Extinct Pleistocene megafauna found in caves – such as giant ground sloths in South America, cave bears in Europe, and marsupial lions in Australia – are good examples.

However, if you want your remains to become a fossil that lasts for millions of years, then you really want minerals to seep through your bones and replace them with harder substances. This process, known as ‘permineralisation’, is what typically creates a fully-fledged fossil. It can take millions of years.

As a result, you might skip the coffin. Bones permineralise most rapidly when mineral-rich water can flow through them, imbuing them with things like iron and calcium. A coffin might keep the skeleton nicely together, but it would interfere with this process.

There is a way a coffin might work, though. Mike Archer, a palaeontologist at the University of New South Wales, suggests burial in a concrete coffin filled with sand and with hundreds of 5mm holes drilled into the sides. This then needs to be buried deep enough that groundwater can pass through.

“If you want to be a classic bony fossil, a bit like something from Dinosaur Provincial Park in Canada, then something like a [coarse] river sand would be pretty good,” says Syme. “All the soft tissues would be destroyed and you’d be left with this beautifully articulated skeleton.”

In terms of the minerals, calcium ions which can precipitate into calcite, a form of calcium carbonate, are especially good. “These can start to cement or cover the body which will protect it in the long run, because given time it will most likely be buried at a greater depth,” Syme says.

Deliberately seeding your corpse with the appropriate minerals, such as calcite or gypsum, might be a way to accelerate this. Encouraging the growth of tough iron-rich minerals would also be sensible as they withstand weathering well in the long run.

If you want to personalise your fossil further, add colour with some copper

If you want to personalise your fossil further, add colour with some copper (Credit: Alamy)

Silicates, from the sand, are also a nice durable mineral to have incorporated. Archer even suggests getting buried with copper strips and nickel pellets if you fancy fossilised bones and teeth with a nice blue-green colour to them.

4. Avoid the edges of tectonic plates

If you made it through the first few hundred thousand years and minerals begin to replace your bones, congratulations! You’ve successfully become a fossil. As sediments build up on top and you get pushed deeper into Earth’s crust, the heat and pressure will aid the process further.

But it’s not a done deal yet. Your fossil might still shift to such depths that it could be melted by the Earth’s heat and pressure.

Don’t want that to happen? Steer clear of the edges of tectonic plates, where the crust is going to eventually get sucked under the surface. One such subduction zone is Iran, where the Eurasian Plate is rising over the Iranian Plate.

5. Get discovered

Now you need to think about the potential for rediscovery.

If you want somebody to chance upon your carefully preserved fossil one day, you need to plan for burial in a spot that currently is low enough to accumulate the necessary sediments for deep burial – but that will eventually be pushed up again. In other words, you need a place with uplift where weathering and erosion will eventually scour off the surface layers, exposing you.

The Dead Sea may be a good place to preserve your fossil

Good for more than floating, the Dead Sea may be a good place to preserve your fossil (Credit: Getty)

One good spot might be the Mediterranean Sea, Syme says; it’s getting shallower as Africa is pushed towards Europe. Other small, inland seas that will fill with sediment are good bets, too.

“Perhaps the Dead Sea,” she says. “The high salt would preserve and pickle you.”

6. Or go rogue

We’ve covered the standard method for hard, durable fossils with bone largely replaced by rock. But there are some oddball methods to consider, too.

Top of the list is amber. There are astounding fossils perfectly preserved in this gemstone made of tree resin – such as recent finds of birds, lizards and even a feathered dinosaur tail in Myanmar. “If you can find a large enough amount of tree sap and get covered in amber, that’s going to be the best way to preserve your soft tissues as well as your bones,” Syme says. “But it’s obviously pretty difficult for such a large animal.”

Can’t find enough amber? The next option is tar pits of the kind that have preserved sabre-toothed cats and mammoths at La Brea in Los Angeles. Although here you would mostly likely end up disarticulated, your bones jumbled in with other animals. There’s also freezing on a mountain or in a glacier, like Ötzi the iceman, found in the European Alps in 1991.

Where Ötzi the iceman met his fate

Where Ötzi the iceman met his fate may not seem very comfortable, but it proved key for preserving his remains (Credit: Alamy)

Another route might be natural mummification, with your body left to dry in a cave system. “There are a lot of cave system remains that get covered with calcium from groundwater, which also forms stalactites and stalagmites,” Syme says. “People like caving and so if the cave systems still exist in the future, they might happen upon you.”

One final method to preserve your corpse almost indefinitely, though not in the form of a fossil, would be launching you into space – or leaving you on the surface of a geologically inert celestial body with no atmosphere, such as the Moon.

“The vacuum of space would be very good if you want your body to remain perpetually non-decaying,” Syme says. She adds that you could attach a radio beacon if you want to get found again in the distant future.

7. Leave a little something extra

Assuming you are found millions of years hence, what else might be preserved alongside you?

Plastics (fidget spinners, anyone?), other oil-derived products that don’t biodegrade and inert metals, like alloys, gold and rare metals of the kind found in mobile phones, all might last as long.

Will mobile phones be one of the artefacts we leave for future generations?

Will mobile phones be one of the artefacts we leave for generations far in the future? (Credit: Getty)

Glass is durable too, and can withstand high temperatures and pressures. You can imagine finding the “outlines or shape of smartphones,” Syme says. Archer notes that the durability of glass means you could chisel ‘ENJOY!’ on a small sheet of glass in a concrete coffin with your body and it would be there to find with your fossil.

“To be 100% sure I would use diamond,” Syme adds – it’s immensely stable. Using a laser, you could etch a letter explaining the lengths you went to to get fossilised.

If you also want to pre-plan your archaeological context, Syme believes bitumen highways and the foundations of skyscrapers are contenders. “We’ve dug down deep into the ground to build these things. You’ll be able to see… the layouts of cities still there,” she says.

Remember, the words you write will fade and your deeds will be forgotten. But a fossil? That, perhaps, could last forever.

Anúncios

California drought causing valley land to sink (Science Daily)

Date:
August 20, 2015
Source:
NASA/Jet Propulsion Laboratory
Summary:
As Californians continue pumping groundwater in response to the historic drought, the California Department of Water Resources has released a new NASA report showing land in the San Joaquin Valley is sinking faster than ever before, nearly 2 inches (5 centimeters) per month in some locations.

Total subsidence in California’s San Joaquin Valley for the period May 3, 2014 to Jan. 22, 2015, as measured by Canada’s Radarsat-2 satellite. Two large subsidence bowls are evident, centered on Corcoran and south of El Nido. Credit: Canadian Space Agency/NASA/JPL-Caltech

As Californians continue pumping groundwater in response to the historic drought, the California Department of Water Resources has released a new NASA report showing land in the San Joaquin Valley is sinking faster than ever before, nearly 2 inches (5 centimeters) per month in some locations.

“Because of increased pumping, groundwater levels are reaching record lows — up to 100 feet (30 meters) lower than previous records,” said Department of Water Resources Director Mark Cowin. “As extensive groundwater pumping continues, the land is sinking more rapidly and this puts nearby infrastructure at greater risk of costly damage.”

Sinking land, known as subsidence, has occurred for decades in California because of excessive groundwater pumping during drought conditions, but the new NASA data show the sinking is happening faster, putting infrastructure on the surface at growing risk of damage.

NASA obtained the subsidence data by comparing satellite images of Earth’s surface over time. Over the last few years, interferometric synthetic aperture radar (InSAR) observations from satellite and aircraft platforms have been used to produce maps of subsidence with approximately centimeter-level accuracy. For this study, JPL researchers analyzed satellite data from Japan’s PALSAR (2006 to 2010); and Canada’s Radarsat-2 (May 2014 to January 2015), and then produced subsidence maps for those periods. High-resolution InSAR data were also acquired along the California Aqueduct by NASA’s Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) (2013 to 2015) to identify and quantify new, highly localized areas of accelerated subsidence along the aqueduct that occurred in 2014. The California Aqueduct is a system of canals, pipelines and tunnels that carries water collected from the Sierra Nevada Mountains and Northern and Central California valleys to Southern California.

Using multiple scenes acquired by these systems, the JPL researchers were able to produce time histories of subsidence at selected locations, as well as profiles showing how subsidence varies over space and time.

“This study represents an unprecedented use of multiple satellites and aircraft to map subsidence in California and address a practical problem we’re all facing,” said JPL research scientist and report co-author Tom Farr. “We’re pleased to supply the California DWR with information they can use to better manage California’s groundwater. It’s like the old saying: ‘you can’t manage what you don’t measure’.”

Land near Corcoran in the Tulare basin sank 13 inches (33 centimeters) in just eight months — about 1.6 inches (4 centimeters) per month. One area in the Sacramento Valley was sinking approximately half-an-inch (1.3 centimeters) per month, faster than previous measurements.

Using the UAVSAR data, NASA also found areas near the California Aqueduct sank up to 12.5 inches (32 centimeters), with 8 inches (20 centimeters) of that occurring in just four months of 2014.

“Subsidence is directly impacting the California Aqueduct, and this NASA technology is ideal for identifying which areas are subsiding the most in order to focus monitoring and repair efforts,” said JPL research scientist and study co-author Cathleen Jones. “Knowledge is power, and in this case knowledge can save water and help the state better maintain this critical element of the state’s water delivery system.” UAVSAR flies on a C-20A research aircraft based at NASA’s Armstrong Flight Research Center facility in Palmdale, California.

The increased subsidence rates have the potential to damage local, state and federal infrastructure, including aqueducts, bridges, roads and flood control structures. Long-term subsidence has already destroyed thousands of public and private groundwater well casings in the San Joaquin Valley. Over time, subsidence can permanently reduce the underground aquifer’s water storage capacity.

“Groundwater acts as a savings account to provide supplies during drought, but the NASA report shows the consequences of excessive withdrawals as we head into the fifth year of historic drought,” Director Cowin said. “We will work together with counties, local water districts, and affected communities to identify ways to slow the rate of subsidence and protect vital infrastructure such as canals, pumping stations, bridges and wells.”

NASA will also continue its subsidence monitoring, using data from the European Space Agency’s recently launched Sentinel-1 mission to cover a broader area and identify more vulnerable locations.

DWR also completed a recent land survey along the Aqueduct — which found 70-plus miles (113-plus kilometers) in Fresno, Kings and Kern counties sank more than 1.25 feet (0.4 meters) in two years — and will now conduct a system-wide evaluation of subsidence along the California Aqueduct and the condition of State Water Project facilities. The evaluation will help the department develop a capital improvement program to repair damage from subsidence. Past evaluations found that segments of the Aqueduct from Los Banos to Lost Hills sank more than 5 feet (1.5 meters) since construction.

NASA and the Indian Space Research Organisation are jointly developing the NASA-ISRO Synthetic Aperture Radar (NISAR) mission. Targeted to launch in 2020, NISAR will make global measurements of the causes and consequences of land surface changes. Potential areas of research include ecosystem disturbances, ice sheet collapse and natural hazards. The NISAR mission is optimized to measure subtle changes of Earth’s surface associated with motions of the crust and ice surfaces. NISAR will improve our understanding of key impacts of climate change and advance our knowledge of natural hazards.

The report, Progress Report: Subsidence in the Central Valley, California, prepared for DWR by researchers at NASA’s Jet Propulsion Laboratory, Pasadena, California, is available at: http://water.ca.gov/groundwater/docs/NASA_REPORT.pdf (14 MB)

Previsão do clima: terremotos intermitentes (Folha de S.Paulo)

Marcelo Leite, 03/05/2015  01h57

Depois de Katmandu, o terremoto no Nepal sacudiu também uma noção preconcebida comum entre jornalistas de ciência – esta coluna, por exemplo, foi abalada por um tuíte de Matthew Shirts, que levava para uma reportagem da revista “Newsweek”.

A leitura do texto, “Mais Terremotos Fatais Virão, Alertam Cientistas da Mudança do Clima”, trouxe à memória um momento constrangedor. Que o relato sirva para desencorajar nossa tendência a acreditar em verdades estabelecidas.

Certa vez um colega de redação perguntou se eu poderia escrever para explicar por que tsunamis estavam se tornando mais frequentes e qual era a relação disso com o aquecimento global. Segurei a vontade de rir e expliquei, condescendente, que processos climáticos não tinham o poder de desencadear eventos geológicos.

Não é bem assim. Há pesquisadores respeitáveis investigando a hipótese de que a mudança climática deflagrada pelo aquecimento global possa, sim, tornar terremotos e erupções vulcânicas mais frequentes.

Não seria nada inédito na história da Terra. Um exemplo recentíssimo na escala geológica (o planeta tem mais de 4 bilhões de anos) ocorreu entre 20 mil e 12 mil anos atrás, ao término do último período glacial.

A retração de geleiras continentais com quilômetros de espessura aliviou a pressão sobre a crosta terrestre o bastante para desencadear intensa atividade vulcânica. Há boas evidências disso em lugares como a Islândia.

O geólogo britânico Bill McGuire tem uma teoria ainda mais preocupante. Ele acha que a elevação dos mares em 100 m, causada pelo derretimento das calotas de gelo, teria deflagrado também terremotos e tsunamis (o que poderia repetir-se a partir de agora, com o aquecimento da atmosfera).

O imenso volume de água adicionado aos oceanos, ao pressionar suas bordas, teria desestabilizado as falhas geológicas próximas da costa, causando os tremores e colapsos submarinos que levantam ondas colossais. Mas a hipótese de McGuire, detalhada no livro “Acordando o Gigante”, ainda carece de medições e dados para ser aceita.

No caso do terremoto de Katmandu, o mecanismo pressuposto para pôr a culpa no clima é outro: chuva. Não uma pancada qualquer, mas as poderosas monções que castigam Índia e Nepal de junho a agosto.

Tamanho volume de água, que perde só para o movimentado na bacia Amazônica, seria capaz de alterar o balanço do estresse entre as placas Indo-Australiana e Asiática. O geólogo argelino Pierre Bettinelli, então no CalTech, mostrou que a atividade sísmica nos Himalaias é duas vezes mais intensa no inverno e atribuiu isso à gangorra de pressões entre os dois lados da falha tectônica.

Falta provar, claro. Mas que é instigante, isso é.

Quanto a terremotos causados pelo aquecimento global, ninguém precisa sair comprando kits de sobrevivência. O degelo da última glaciação demorou milhares de anos, e as piores previsões para a subida no nível dos oceanos indicam não muito mais que 1 m ou 2 m até o final deste século.

Ninguém está a salvo de tsunamis, porém. Há alguma chance – uma vez a cada 10 mil anos, talvez – de que o litoral brasileiro seja atingido por um deles, como pode ter ocorrido com São Vicente em 1541, após cataclisma nalgum ponto do Atlântico.

Imagining the Anthropocene (AEON)

The Anthropocene idea has been embraced by Earth scientists and English professors alike. But how useful is it?

Jedediah Purdy is Professor of Law at Duke University in North Carolina. His forthcoming book is After Nature: A Politics for the Anthropocene.

Edited by Ross Andersen

Officially, for the past 11,700 years we have been living in the Holocene epoch. From the Greek for ‘totally new’, the Holocene is an eyeblink in geological time. In its nearly 12,000 years, plate tectonics has driven the continents a little more than half a mile: a reasonably fit person could cover the scale of planetary change in a brisk eight-minute walk. It has been a warm time, when temperature has mattered as much as tectonics. Sea levels rose 115 feet from ice melt, and northern landscapes rose almost 600 feet, as they shrugged off the weight of their glaciers.

But the real news in the Holocene has been people. Estimates put the global human population between 1 million and 10 million at the start of the Holocene, and keep it in that range until after the agricultural revolution, some 5,000 years ago. Since then, we have made the world our anthill: the geological layers we are now laying down on the Earth’s surface are marked by our chemicals and industrial waste, the pollens of our crops, and the absence of the many species we have driven to extinction. Rising sea levels are now our doing. As a driver of global change, humanity has outstripped geology.

This is why, from the earth sciences to English departments, there’s a veritable academic stampede to declare that we live in a new era, the Anthropocene – the age of humans. Coined by the ecologist Eugene Stoermer in the 1980s and brought to public attention in 2000 by the Nobel Prize-winning atmospheric scientist Paul Crutzen, the term remains officially under consideration at the Stratigraphy Commission of the Geological Society of London.

The lack of an official decision has set up the Anthropocene as a Rorschach blot for discerning what commentators think is the epochal change in the human/nature relationship. The rise of agriculture in China and the Middle East? The industrial revolution and worldwide spread of farming in the Age of Empire? The Atomic bomb? From methane levels to carbon concentration, from pollen residue to fallout, each of these changes leaves its mark in the Earth’s geological record. Each is also a symbol of a new set of human powers and a new way of living on Earth.

The most radical thought identified with the Anthropocene is this: the familiar contrast between people and the natural world no longer holds. There is no more nature that stands apart from human beings. There is no place or living thing that we haven’t changed. Our mark is on the cycle of weather and seasons, the global map of bioregions, and the DNA that organises matter into life. The question is no longer how to preserve a wild world from human intrusion; it is what shape we will give to a world we can’t help changing.

The discovery that nature is henceforth partly a human creation makes the Anthropocene the latest of three great revolutions: three kinds of order once thought to be given and self-sustaining have proved instead to be fragile human creations. The first to fall was politics. Long seen as part of divine design, with kings serving as the human equivalents of eagles in the sky and oaks in the forest, politics proved instead a dangerous but inescapable form of architecture – a blueprint for peaceful co‑existence, built with crooked materials. Second came economics. Once presented as a gift of providence or an outgrowth of human nature, economic life, like politics, turned out to be a deliberate and artificial achievement. (We are still debating the range of shapes it can take, from Washington to Greece to China.) Now, in the Anthropocene, nature itself has joined the list of those things that are not natural. The world we inhabit will henceforth be the world we have made.

The revolution in ideas that the Anthropocene represents is rooted in hundreds of eminently practical problems. The conversation about climate change has shifted from whether we can keep greenhouse-gas concentrations below key thresholds to how we are going to adapt when they cross those thresholds. Geo‑engineering, deliberately intervening in planetary systems, used to be the unspeakable proposal in climate policy. Now it is in the mix and almost sure to grow more prominent. As climate change shifts ecological boundaries, issues such as habitat preservation come to resemble landscape architecture. We can’t just pen in animals to save them; they need landscape-scale corridors and other help in migrating as their habitats move. There is open talk in law-and-policy circles about triage in species preservation – asking what we can save, and what we most want to save.

What work is this idea of the Anthropocene doing in culture and politics? As much as a scientific concept, the Anthropocene is a political and ethical gambit. Saying that we live in the Anthropocene is a way of saying that we cannot avoid responsibility for the world we are making. So far so good. The trouble starts when this charismatic, all-encompassing idea of the Anthropocene becomes an all-purpose projection screen and amplifier for one’s preferred version of ‘taking responsibility for the planet’.

Peter Kareiva, the controversial chief scientist of the Nature Conservancy, uses the theme ‘Conservation in the Anthropocene’ to trash environmentalism as philosophically naïve and politically backward. Kareiva urges conservationists to give up on wilderness and embrace what the writer Emma Marris calls the ‘rambunctious garden’. Specifically, Kareiva wants to rank ecosystems by the quality of ‘ecosystem services’ they provide for human beings instead of ‘pursuing the protection of biodiversity for biodiversity’s sake’. He wants a pro‑development stance that assumes that ‘nature is resilient rather than fragile’. He insists that: ‘Instead of scolding capitalism, conservationists should partner with corporations in a science-based effort to integrate the value of nature’s benefits into their operations and cultures.’ In other words, the end of nature is the signal to carry on with green-branded business as usual, and the business of business is business, as the Nature Conservancy’s partnerships with Dow, Monsanto, Coca-Cola, Pepsi, J P Morgan, Goldman Sachs and the mining giant Rio Tinto remind us.

Kareiva is a favourite of Andrew Revkin, the roving environmental maven of The New York Times Magazine, who touts him as a paragon of responsibility-taking, a leader among ‘scholars and doers who see that new models for thinking and acting are required in this time of the Anthropocene’. This pair and their friends at the Breakthrough Institute in California can be read as making a persistent effort to ‘rebrand’ environmentalism as humanitarian and development-friendly (and capture speaking and consultancy fees, which often seem to be the major ecosystem services of the Anthropocene). This is itself a branding strategy, an opportunity to slosh around old plonk in an ostentatiously shiny bottle.

Elsewhere in The New York Times Magazine, you can enjoy the other end of the Anthropocene projection screen, from business-as-usual to this-changes-everything. In his essay ‘Learning How to Die in the Anthropocene’ (2013), the Princeton scholar and former soldier Roy Scranton writes: ‘this civilisation is already dead’ (emphasis original) and insists that the only way forward is ‘to realise there’s nothing we can do to save ourselves’ and therefore ‘get down to the hard work … without attachment or fear’. He concludes: ‘If we want to learn to live in the Anthropocene, we must first learn how to die.’

Other humanists bring their own preoccupations to a sense of gathering apocalypse. In his influential essay ‘The Climate of History’ (2008), Dipesh Chakrabarty, a theory-minded historian at the University of Chicago, proposes that the Anthropocene throws into question all received accounts of human history, from Whiggish optimism to his own post-colonial postmodernism. He asks anxiously: ‘Has the period from 1750 to the present been one of freedom or that of the Anthropocene?’ and concludes that the age requires a new paradigm of thought, a ‘negative universal history’.

In their introduction to Ecocriticism (2012), a special issue of American Literature, the English scholars Monique Allewaert of the University of Wisconsin-Madison and Michael Ziser of the University of California Davis describe the Anthropocene as best captured in ‘a snapshot of the anxious affect of the modern world as it destroys itself – and denies even its own traces’.

The Anthropocene does not seem to change many minds. But it does turn them up to 11

All of these people (except for the branding opportunists) are trying, with more or less success, to ask how the Anthropocene changes the projects to which they’ve given chunks of their lives. Some far-ranging speculation and sweeping summaries are to be expected, and forgiven. Nonetheless, something in the Anthropocene idea seems to provoke heroic thinking, a mood and rhetoric of high stakes, of the human mind pressed up against the wall of apocalypse or arrived at the end of nature and history.

In this provocative defect, Anthropocene talk is a discourse of responsibility, to borrow a term from Mark Greif’s study of mid-20th-century American thought, The Age of the Crisis of Man (2015). Greif argues that a high-minded (but often middle-brow) strain of rhetoric responded to the horrors of the world wars and the global struggles thereafter with a blend of urgent language and sweeping concepts (or pseudo-concepts): responsibility, the fate of man, the urgency of now. Greif describes discourses of responsibility as attempts to turn words and thoughts, uttered in tones of utmost seriousness, into a high form of action. All of this is recognisable in Anthropocene talk. The Anthropocene does not seem to change many minds, strictly speaking, on point of their cherished convictions. But it does turn them up to 11.

On the whole, this is the inevitable and often productive messiness that accompanies a new way of seeing, one that unites many disparate events into a single pattern. As an offer to unify what might seem unrelated, ‘the Anthropocene’ is an attempt to do the same work that ‘the environment’ did in the 1960s and early ’70s: meld problems as far-flung as extinction, sprawl, litter, national parks policy, and the atom bomb into a single phenomenon called ‘the ecological crisis’. Such a classification is always somewhat arbitrary, though often only in the trivial sense that there are many ways to carve up the world. However arbitrary, it becomes real if people treat it as real, by forming movements, proposing changes, and passing laws aimed at ‘the environment’.

We know what the concept ‘the environment’ has wrought but what will the Anthropocene be like? To put this over-dramatised idea in the least heroic garb possible, what will the weather be like in the Anthropocene? And how will we talk about the weather there?

For all the talk of crisis that swirls around the Anthropocene, it is unlikely that a changing Earth will feel catastrophic or apocalyptic. Some environmentalists still warn of apocalypse to motivate could-be, should-be activists; but geologic time remains far slower than political time, even when human powers add a wobble to the planet. Instead, the Anthropocene will be like today, only more so: many systems, from weather to soil to your local ecosystem, will be in a slow-perennial crisis. And where apocalyptic change is a rupture in time, a slow crisis feels normal. It feels, in fact, natural.

So the Anthropocene will feel natural. I say this not so much because of the controversial empirics-cum-mathematics of the climate-forecasting models as because of a basic insight of modernity that goes back to Rousseau: humanity is the adaptable species. What would have been unimaginable or seemed all but unintelligible 100 years ago, let alone 500 (a sliver of time in the evolutionary life of a species), can become ordinary in a generation. That is how long it took to produce ‘digital natives’, to accustom people to electricity and television, and so on for each revolution in our material and technological world. It takes a great deal of change to break through this kind of adaptability.

This is all the more so because rich-country humanity already lives in a constant technological wrestling match with exogenous shocks, which are going to get more frequent and more intense in the Anthropocene. Large parts of North America regularly experience droughts and heat waves that would devastate a simpler society than today’s US. Because the continent is thoroughly engineered, from the water canals of the West to the irrigation systems of the Great Plains to air conditioning nearly everywhere, these are experienced as inconvenience, as mere ‘news’. The same events, in poorer places, are catastrophes.

Planetary changes will amplify the inequalities that sort out those who get news from those who get catastrophes; but these inequalities, arising as they do from a post-natural nature, will feel as if they were built into the world itself. Indeed, nature has always served to launder the inequalities that humans produce. Are enslaved people kept illiterate and punished brutally when they are not servile? Then ignorance and servility must be in their nature, an idea that goes back in a continuous line to Aristotle. The same goes for women, with some edits to their nature: docile, nurturing, delicate, hysterical, etc. It was not until Harriet Taylor and John Stuart Mill worked together on The Subjection of Women (published under his name alone in 1869), that English-language philosophy produced a basic challenge to millennia of nature-talk about sexual difference.

The expulsion of Native Americans was ‘justified’ on several versions of nature. Maybe they were racially different. Maybe their climate made them weak and irrational, unable to cultivate the land or resist European settlement. (Colonists briefly embraced this idea, then grew uneasy when they realised that the North American climate was now theirs; by the time of American independence, they raced to reject climatic theories of racial character.) Maybe Native Americans had simply failed to fulfil the natural duty of all mankind, to clear and plant the wilderness and make it bloom like an English garden, an idea that many theorists of natural law advanced in the 17th and 18th centuries. One way or another, nature was a kind of ontological insurance policy for human injustice.

And now? Well, it’s common wisdom that rising sea levels will first affect some of the world’s poorest people, notably in Bangladesh and coastal India. But it’s much worse than that grim geographic coincidence. Wealth has always meant some protection from nature’s cruel measures. In fact, that is the first spur to technology and development of all kinds: not to be killed. Tropical diseases with changing range will find some populations well-equipped with vaccination and medicine, others struggling with bad government and derelict health systems. When seas rise fast, even the feckless but rich US will begin adapting fast, and coastal flooding will be classified in the rich-world mind as a catastrophe of the poor.

So will starvation. A legal regime of unequal Anthropocene vulnerability is well underway. Take the vast, long-term leases that Chinese companies have entered into for some of Africa’s richest farmland. When drought, soil exhaustion or crop crisis puts a pinch on global food supply, contracts and commerce will pull trillions of calories to fat-and-happy Beijing. This is, of course, only the latest chapter in centuries of imperialism and post-imperial, officially voluntary global inequality. But it is the chapter that we the living are writing.

Neoliberal environmentalism aims to bring nature fully into the market, merging ecology and economy

For the moment, Anthropocene inequality has a special affinity with neoliberalism, the global extension of a dogmatic market logic and increasingly homogenous market forms, along with an accompanying ideology insisting that, if the market is not beyond reproach, it is at least beyond reform: there is no alternative. Where previous episodes of global ecological inequality took place under direct imperial administration – witness the Indian famines of the late 19th century, suffered under British rule – ours is emerging under the sign of free contract. Anthropocene inequality is thus being doubly laundered: first as natural, second as the voluntary (and presumptively efficient) product of markets. Because human activity now shapes the ‘natural’ world at every point, it is especially convenient for that world-shaping activity to proceed in its own pseudo-natural market.

But Anthropocene problems also put pressure on the authority of economics. Much of environmental economics has been built on the concept of the externality, economist-speak for a side-effect, a harm or benefit that has no price tag, and so is ignored in market decisions. Air pollution – free to the polluter – is the classic bad side-effect, or ‘negative externality’. Wetlands – not valued on the real-estate market, but great sources of filtration, purification and fertility, which would otherwise cost a lot to replicate – are the model positive externality. So neoliberal environmentalism, which Kareiva’s Nature Conservancy has been cultivating, aims to bring nature fully into the market, finding a place in the bottom line for all former side-effects, and fully merging ecology and economy.

In a climate-changed Anthropocene, the side-effects overwhelm the ‘regular’ market in scale and consequence. And there is no ‘neutral’, purely market-based way to put a value on side-effects. Take the example of carbon emissions. It is possible to create a market for emissions, as Europe, California and other jurisdictions have done; but at the base of that market is a political decision about how to value the economic activity that emits carbon against all the (uncertain and even speculative) effects of the emissions. The same point holds for every (post-)natural system on an Anthropocene planet. Ultimately, the question is the value of life, and ways of life. There is no correct technocratic answer.

The shape of the Anthropocene is a political, ethical and aesthetic question. It will answer questions about what life is worth, what people owe one another, and what in the world is awesome or beautiful enough to preserve or (re)create. Either the answers will reproduce and amplify existing inequality or they will set in motion a different logic of power. Either the Anthropocene will be democratic or it will be horrible.

A democratic Anthropocene would start from a famous observation of the economics Nobel Prize laureate Amartya Sen: no minimally democratic society has ever suffered a famine. Natural catastrophes are the joint products of natural and human systems. Your vulnerability to disaster is often a direct expression of your standing in a political (and economic) order. The Anthropocene stands for the intensifying merger of ecology, economics and politics, and one’s standing in those systems will increasingly be a single question.

But talk of democracy here is – like much about the Anthropocene – in danger of becoming abstract and moralising. Reflecting on a democratic Anthropocene becomes an inadvertent meditation on the devastating absence of any agent – a state, or even a movement – that could act on the scale of the problem. Indeed, it reveals that there is no agent that could even define the problem. If the Anthropocene is about the relationship between humanity and the planet, well, there is no ‘humanity’ that agrees on any particular meaning and imperative of climate change, extinction, toxification, etc. To think about the Anthropocene is to think about being able to do nothing about everything. No wonder the topic inspires compensatory fantasies that the solution lies in refining the bottom line or honing personal enlightenment – always, to be sure, in the name of some fictive ‘we’.

This returns us to the basic problem that the Anthropocene drives home: as Hannah Arendt observed in The Origins of Totalitarianism (1951), the idea of human rights – such as the right to democratic standing in planetary change – is a chimera and a cruel taunt without a political community that can make it good through robust institutions and practices. The Anthropocene shows how far the world is from being such a polity, or a federation of such polities, and how much is at stake in that absence. The world is too much with us. Worse, there is no ‘we’ to be with it.

In the face of all these barriers, what could all this talk about the Anthropocene possibly accomplish? Ironically, a useful comparison lies in Arendt’s target, the mere idea of human rights. While mere ideas are in fact sorry comforts in an unmanageable situation, they can be the beginning of demands, projects, even utopias, that enable people to organise in new ways to pursue them. The idea of human rights has gained much of its force this way, as a prism through which many efforts are focused and/or refracted.

A democratic Anthropocene is just a thought for now, but it can also be a tool that activists, thinkers and leaders use to craft challenges and invitations that bring some of us a little closer to a better possible world, or a worse one. The idea that the world people get to inhabit will only be the one they make is, in fact, imperative to the development of a political and institutional programme, even if the idea itself does not tell anyone how to do that. There might not be a world to win, or even save, but there is a humanity to be shaped and reshaped, freely and always in partial and provisional ways, that can begin intending the world it shapes.

31 March 2015

Popular now

Anthropocene: The human age (Nature)

Momentum is building to establish a new geological epoch that recognizes humanity’s impact on the planet. But there is fierce debate behind the scenes.

Richard Monastersky

11 March 2015

Illustration by Jessica Fortner

Almost all the dinosaurs have vanished from the National Museum of Natural History in Washington DC. The fossil hall is now mostly empty and painted in deep shadows as palaeobiologist Scott Wing wanders through the cavernous room.

Wing is part of a team carrying out a radical, US$45-million redesign of the exhibition space, which is part of the Smithsonian Institution. And when it opens again in 2019, the hall will do more than revisit Earth’s distant past. Alongside the typical displays of Tyrannosaurus rex and Triceratops, there will be a new section that forces visitors to consider the species that is currently dominating the planet.

“We want to help people imagine their role in the world, which is maybe more important than many of them realize,” says Wing.

This provocative exhibit will focus on the Anthropocene — the slice of Earth’s history during which people have become a major geological force. Through mining activities alone, humans move more sediment than all the world’s rivers combined. Homo sapiens has also warmed the planet, raised sea levels, eroded the ozone layer and acidified the oceans.

Given the magnitude of these changes, many researchers propose that the Anthropocene represents a new division of geological time. The concept has gained traction, especially in the past few years — and not just among geoscientists. The word has been invoked by archaeologists, historians and even gender-studies researchers; several museums around the world have exhibited art inspired by the Anthropocene; and the media have heartily adopted the idea. “Welcome to the Anthropocene,” The Economist announced in 2011.

The greeting was a tad premature. Although the term is trending, the Anthropocene is still an amorphous notion — an unofficial name that has yet to be accepted as part of the geological timescale. That may change soon. A committee of researchers is currently hashing out whether to codify the Anthropocene as a formal geological unit, and when to define its starting point.

But critics worry that important arguments against the proposal have been drowned out by popular enthusiasm, driven in part by environmentally minded researchers who want to highlight how destructive humans have become. Some supporters of the Anthropocene idea have even been likened to zealots. “There’s a similarity to certain religious groups who are extremely keen on their religion — to the extent that they think everybody who doesn’t practise their religion is some kind of barbarian,” says one geologist who asked not to be named.

The debate has shone a spotlight on the typically unnoticed process by which geologists carve up Earth’s 4.5 billion years of history. Normally, decisions about the geological timescale are made solely on the basis of stratigraphy — the evidence contained in layers of rock, ocean sediments, ice cores and other geological deposits. But the issue of the Anthropocene “is an order of magnitude more complicated than the stratigraphy”, says Jan Zalasiewicz, a geologist at the University of Leicester, UK, and the chair of the Anthropocene Working Group that is evaluating the issue for the International Commission on Stratigraphy (ICS).

Written in stone

For geoscientists, the timescale of Earth’s history rivals the periodic table in terms of scientific importance. It has taken centuries of painstaking stratigraphic work — matching up major rock units around the world and placing them in order of formation — to provide an organizing scaffold that supports all studies of the planet’s past. “The geologic timescale, in my view, is one of the great achievements of humanity,” says Michael Walker, a Quaternary scientist at the University of Wales Trinity St David in Lampeter, UK.

Walker’s work sits at the top of the timescale. He led a group that helped to define the most recent unit of geological time, the Holocene epoch, which began about 11,700 years ago.

Sources: Dams/Water/Fertilizer, IGBP; Fallout, Ref. 5; Map, E. C. Ellis Phil. Trans. R. Soc. A 369, 1010–1035 (2011); Methane, Ref. 4

The decision to formalize the Holocene in 2008 was one of the most recent major actions by the ICS, which oversees the timescale. The commission has segmented Earth’s history into a series of nested blocks, much like the years, months and days of a calendar. In geological time, the 66 million years since the death of the dinosaurs is known as the Cenozoic era. Within that, the Quaternary period occupies the past 2.58 million years — during which Earth has cycled in and out of a few dozen ice ages. The vast bulk of the Quaternary consists of the Pleistocene epoch, with the Holocene occupying the thin sliver of time since the end of the last ice age.

When Walker and his group defined the beginning of the Holocene, they had to pick a spot on the planet that had a signal to mark that boundary. Most geological units are identified by a specific change recorded in rocks — often the first appearance of a ubiquitous fossil. But the Holocene is so young, geologically speaking, that it permits an unusual level of precision. Walker and his colleagues selected a climatic change — the end of the last ice age’s final cold snap — and identified a chemical signature of that warming at a depth of 1,492.45 metres in a core of ice drilled near the centre of Greenland1. A similar fingerprint of warming can be seen in lake and marine sediments around the world, allowing geologists to precisely identify the start of the Holocene elsewhere.

“The geologic timescale, in my view, is one of the great achievements of humanity.”

Even as the ICS was finalizing its decision on the start of the Holocene, discussion was already building about whether it was time to end that epoch and replace it with the Anthropocene. This idea has a long history. In the mid-nineteenth century, several geologists sought to recognize the growing power of humankind by referring to the present as the ‘anthropozoic era’, and others have since made similar proposals, sometimes with different names. The idea has gained traction only in the past few years, however, in part because of rapid changes in the environment, as well as the influence of Paul Crutzen, a chemist at the Max Plank Institute for Chemistry in Mainz, Germany.

Crutzen has first-hand experience of how human actions are altering the planet. In the 1970s and 1980s, he made major discoveries about the ozone layer and how pollution from humans could damage it — work that eventually earned him a share of a Nobel prize. In 2000, he and Eugene Stoermer of the University of Michigan in Ann Arbor argued that the global population has gained so much influence over planetary processes that the current geological epoch should be called the Anthropocene2. As an atmospheric chemist, Crutzen was not part of the community that adjudicates changes to the geological timescale. But the idea inspired many geologists, particularly Zalasiewicz and other members of the Geological Society of London. In 2008, they wrote a position paper urging their community to consider the idea3.

Those authors had the power to make things happen. Zalasiewicz happened to be a member of the Quaternary subcommission of the ICS, the body that would be responsible for officially considering the suggestion. One of his co-authors, geologist Phil Gibbard of the University of Cambridge, UK, chaired the subcommission at the time.

Although sceptical of the idea, Gibbard says, “I could see it was important, something we should not be turning our backs on.” The next year, he tasked Zalasiewicz with forming the Anthropocene Working Group to look into the matter.

A new beginning

Since then, the working group has been busy. It has published two large reports (“They would each hurt you if they dropped on your toe,” says Zalasiewicz) and dozens of other papers.

The group has several issues to tackle: whether it makes sense to establish the Anthropocene as a formal part of the geological timescale; when to start it; and what status it should have in the hierarchy of the geological time — if it is adopted.

When Crutzen proposed the term Anthropocene, he gave it the suffix appropriate for an epoch and argued for a starting date in the late eighteenth century, at the beginning of the Industrial Revolution. Between then and the start of the new millennium, he noted, humans had chewed a hole in the ozone layer over Antarctica, doubled the amount of methane in the atmosphere and driven up carbon dioxide concentrations by 30%, to a level not seen in 400,000 years.

When the Anthropocene Working Group started investigating, it compiled a much longer long list of the changes wrought by humans. Agriculture, construction and the damming of rivers is stripping away sediment at least ten times as fast as the natural forces of erosion. Along some coastlines, the flood of nutrients from fertilizers has created oxygen-poor ‘dead zones’, and the extra CO2 from fossil-fuel burning has acidified the surface waters of the ocean by 0.1 pH units. The fingerprint of humans is clear in global temperatures, the rate of species extinctions and the loss of Arctic ice.

The group, which includes Crutzen, initially leaned towards his idea of choosing the Industrial Revolution as the beginning of the Anthropocene. But other options were on the table.

Some researchers have argued for a starting time that coincides with an expansion of agriculture and livestock cultivation more than 5,000 years ago4, or a surge in mining more than 3,000 years ago (see ‘Humans at the helm’). But neither the Industrial Revolution nor those earlier changes have left unambiguous geological signals of human activity that are synchronous around the globe (see ‘Landscape architecture’).

This week in Nature, two researchers propose that a potential marker for the start of the Anthropocene could be a noticeable drop in atmospheric CO2 concentrations between 1570 and 1620, which is recorded in ice cores (see page 171). They link this change to the deaths of some 50 million indigenous people in the Americas, triggered by the arrival of Europeans. In the aftermath, forests took over 65 million hectares of abandoned agricultural fields — a surge of regrowth that reduced global CO2.

Landscape architecture

A model of land use, based on human-population estimates, suggests that people modified substantial parts of the continents even thousands of years ago.

Land used intensively by humans.

8,000 years before present (bp)

8,000 years before present (bp)

1,000 years before present (bp)

anthropocene-slideshow-5

Present

anthropocene-slideshow-10

Source: E. C. Ellis Phil. Trans. R. Soc. A 369, 1010–1035 (2011).

In the working group, Zalasiewicz and others have been talking increasingly about another option — using the geological marks left by the atomic age. Between 1945 and 1963, when the Limited Nuclear Test Ban Treaty took effect, nations conducted some 500 above-ground nuclear blasts. Debris from those explosions circled the globe and created an identifiable layer of radioactive elements in sediments. At the same time, humans were making geological impressions in a number of other ways — all part of what has been called the Great Acceleration of the modern world. Plastics started flooding the environment, along with aluminium, artificial fertilizers, concrete and leaded petrol, all of which have left signals in the sedimentary record.

In January, the majority of the 37-person working group offered its first tentative conclusion. Zalasiewicz and 25 other members reported5 that the geological markers available from the mid-twentieth century make this time “stratigraphically optimal” for picking the start of the Anthropocene, whether or not it is formally defined. Zalasiewicz calls it “a candidate for the least-worst boundary”.

The group even proposed a precise date: 16 July 1945, the day of the first atomic-bomb blast. Geologists thousands of years in the future would be able to identify the boundary by looking in the sediments for the signature of long-lived plutonium from mid-century bomb blasts or many of the other global markers from that time.

A many-layered debate

The push to formalize the Anthropocene upsets some stratigraphers. In 2012, a commentary published by the Geological Society of America6 asked: “Is the Anthropocene an issue of stratigraphy or pop culture?” Some complain that the working group has generated a stream of publicity in support of the concept. “I’m frustrated because any time they do anything, there are newspaper articles,” says Stan Finney, a stratigraphic palaeontologist at California State University in Long Beach and the chair of the ICS, which would eventually vote on any proposal put forward by the working group. “What you see here is, it’s become a political statement. That’s what so many people want.”

Finney laid out some of his concerns in a paper7 published in 2013. One major question is whether there really are significant records of the Anthropocene in global stratigraphy. In the deep sea, he notes, the layer of sediments representing the past 70 years would be thinner than 1 millimetre. An even larger issue, he says, is whether it is appropriate to name something that exists mainly in the present and the future as part of the geological timescale.

“It’s become a political statement. That’s what so many people want.”

Some researchers argue that it is too soon to make a decision — it will take centuries or longer to know what lasting impact humans are having on the planet. One member of the working group, Erle Ellis, a geographer at the University of Maryland, Baltimore County, says that he raised the idea of holding off with fellow members of the group. “We should set a time, perhaps 1,000 years from now, in which we would officially investigate this,” he says. “Making a decision before that would be premature.”

That does not seem likely, given that the working group plans to present initial recommendations by 2016.

Some members with different views from the majority have dropped out of the discussion. Walker and others contend that human activities have already been recognized in the geological timescale: the only difference between the current warm period, the Holocene, and all the interglacial times during the Pleistocene is the presence of human societies in the modern one. “You’ve played the human card in defining the Holocene. It’s very difficult to play the human card again,” he says.

Walker resigned from the group a year ago, when it became clear that he had little to add. He has nothing but respect for its members, he says, but he has heard concern that the Anthropocene movement is picking up speed. “There’s a sense in some quarters that this is something of a juggernaut,” he says. “Within the geologic community, particularly within the stratigraphic community, there is a sense of disquiet.”

Zalasiewicz takes pains to make it clear that the working group has not yet reached any firm conclusions.“We need to discuss the utility of the Anthropocene. If one is to formalize it, who would that help, and to whom it might be a nuisance?” he says. “There is lots of work still to do.”

Any proposal that the group did make would still need to pass a series of hurdles. First, it would need to receive a supermajority — 60% support — in a vote by members of the Quaternary subcommission. Then it would need to reach the same margin in a second vote by the leadership of the full ICS, which includes chairs from groups that study the major time blocks. Finally, the executive committee of the International Union of Geological Sciences must approve the request.

At each step, proposals are often sent back for revision, and they sometimes die altogether. It is an inherently conservative process, says Martin Head, a marine stratigrapher at Brock University in St Catharines, Canada, and the current head of the Quaternary subcommission. “You are messing around with a timescale that is used by millions of people around the world. So if you’re making changes, they have to be made on the basis of something for which there is overwhelming support.”

Some voting members of the Quaternary subcommission have told Nature that they have not been persuaded by the arguments raised so far in favour of the Anthropocene. Gibbard, a friend of Zalasiewicz’s, says that defining this new epoch will not help most Quaternary geologists, especially those working in the Holocene, because they tend not to study material from the past few decades or centuries. But, he adds: “I don’t want to be the person who ruins the party, because a lot of useful stuff is coming out as a consequence of people thinking about this in a systematic way.”

If a proposal does not pass, researchers could continue to use the name Anthropocene on an informal basis, in much the same way as archaeological terms such as the Neolithic era and the Bronze Age are used today. Regardless of the outcome, the Anthropocene has already taken on a life of its own. Three Anthropocene journals have started up in the past two years, and the number of papers on the topic is rising sharply, with more than 200 published in 2014.

By 2019, when the new fossil hall opens at the Smithsonian’s natural history museum, it will probably be clear whether the Anthropocene exhibition depicts an official time unit or not. Wing, a member of the working group, says that he does not want the stratigraphic debate to overshadow the bigger issues. “There is certainly a broader point about human effects on Earth systems, which is way more important and also more scientifically interesting.”

As he walks through the closed palaeontology hall, he points out how much work has yet to be done to refashion the exhibits and modernize the museum, which opened more than a century ago. A hundred years is a heartbeat to a geologist. But in that span, the human population has more than tripled. Wing wants museum visitors to think, however briefly, about the planetary power that people now wield, and how that fits into the context of Earth’s history. “If you look back from 10 million years in the future,” he says, “you’ll be able to see what we were doing today.”

Nature 519, 144–147 (12 March 2015), doi:10.1038/519144a

References

  1. Walker, M. et alJ. Quat. Sci. 24317 (2009).
  2. Crutzen, P. J. & Stoermer, E. F. IGBP Newsletter 411718 (2000).
  3. Zalasiewicz. J. et alGSA Today 18(2), 48 (2008).
  4. Ruddiman, W. F. Ann. Rev. Earth. Planet. Sci. 414568 (2013).
  5. Zalasiewicz, J. et alQuatern. Int. http://dx.doi.org/10.1016/j.quaint.2014.11.045 (2015).
  6. Autin, W. J. & Holbrook, J. M. GSA Today 22(7), 6061 (2012).
  7. Finney, S. C. Geol. Soc. Spec. Publ. 3952328 (2013).

Coping with the anthropocene: How we became nature (Science Daily)

Date: March 17, 2015

Source: De Gruyter

Summary: Overpopulation, the greenhouse effect, warming temperatures and overall climate disruption are all well recognized as a major threat to the ecology and biodiversity of the Earth.  The issue of humankind’s negative impact on the environment, albeit hotly debated and continuously present in the public eye, still only leads to limited policy action.


Overpopulation, the greenhouse effect, warming temperatures and overall climate disruption are all well recognized as a major threat to the ecology and biodiversity of the Earth. The issue of mankind’s negative impact on the environment, albeit hotly debated and continuously present in the public eye, still only leads to limited policy action. Urgent action is required, insist Paul Cruzten and Stanislaw Waclawek, the authors of “Atmospheric Chemistry and Climate in the Anthropocene,” published in open access in the new Chemistry-Didactics-Ecology-Metrology.

In their sobering review, Crutzen, the 1995 Nobel Laureate in Chemistry, and Waclawek, outline the development of a new geological epoch — the Anthropocene, where human actions become a global geophysical force, surpassing that of nature itself.

Anthropocene, which relates to the present geological epoch, in which human actions determine the behavior of the planet Earth to a greater degree than other natural processes. The term, coined by American ecologist Eugene F. Stoermer and popularized by Crutzen, introduced the epoch succeeding the Holocene, which is the official term for the present epoch on Geological Time Scale, covering the last 11, 500 years.

Although Anthropocene is not a new concept, it is only now that the authors present stunning evidence in support of their claim. The article describes the negative impact of the human footprint, which ensues a gradual destruction of the Earth. Highlighting different data elements — it yields overwhelming evidence that “man, the eroder” now transforms the atmospheric, geologic, hydrologic, biospheric, and other earth system processes.

The list is long and unforgiving:

· Excessively rapid climate change, so that ecosystems cannot adapt

· The Arctic ocean ice cover is thinner by approximately 40% compared to 20-40 years ago

· Ice loss and the growing sea levels

· Overpopulation (fourfold increase in the 20th century alone)

· Increasing demand for freshwater

· Releases of NO into the atmosphere, resulting in high surface ozone layers

· Loss of agricultural soil through erosion

· Loss of phosphorus. Dangerous depletion in agricultural regions

· Melting supplies of phosphate reserves (leading to serious reduction in crop yield)

Describing the negative impact of human activities on the environment, the authors identify planetary boundaries, as means to attaining global sustainability. It is “a well-documented summary of all humankind actions affecting the environment on all scales. According to Crutzen, we live in a new era, Anthropocene, and our survival fully depends on us. I strongly recommend this unusual publication in the form of highly informative compressed slides and graphs.” says Marina Frontasyeva from the Joint Institute for Nuclear Research in Dubna, Russia. Nature is us, and responding to the Anthropocene means building a culture that grows with the Earth’s biological wealth instead of depleting it.


Journal Reference:

  1. Paul J. Crutzen, Stanisław Wacławek. Atmospheric Chemistry and Climate in the AnthropoceneChemistry-Didactics-Ecology-Metrology, 2015 DOI: 10.1515/cdem-2014-0001

Did a Volcanic Cataclysm 40,000 Years Ago Trigger the Final Demise of the Neanderthals? (Geological Society of America)

19 March 2015

Boulder, Colo., USA – The Campanian Ignimbrite (CI) eruption in Italy 40,000 years ago was one of the largest volcanic cataclysms in Europe and injected a significant amount of sulfur-dioxide (SO2) into the stratosphere. Scientists have long debated whether this eruption contributed to the final extinction of the Neanderthals. This new study by Benjamin A. Black and colleagues tests this hypothesis with a sophisticated climate model.

Black and colleagues write that the CI eruption approximately coincided with the final decline of Neanderthals as well as with dramatic territorial and cultural advances among anatomically modern humans. Because of this, the roles of climate, hominin competition, and volcanic sulfur cooling and acid deposition have been vigorously debated as causes of Neanderthal extinction.

They point out, however, that the decline of Neanderthals in Europe began well before the CI eruption: “Radiocarbon dating has shown that at the time of the CI eruption, anatomically modern humans had already arrived in Europe, and the range of Neanderthals had steadily diminished. Work at five sites in the Mediterranean indicates that anatomically modern humans were established in these locations by then as well.”

“While the precise implications of the CI eruption for cultures and livelihoods are best understood in the context of archaeological data sets,” write Black and colleagues, the results of their study quantitatively describe the magnitude and distribution of the volcanic cooling and acid deposition that ancient hominin communities experienced coincident with the final decline of the Neanderthals.

In their climate simulations, Black and colleagues found that the largest temperature decreases after the eruption occurred in Eastern Europe and Asia and sidestepped the areas where the final Neanderthal populations were living (Western Europe). Therefore, the authors conclude that the eruption was probably insufficient to trigger Neanderthal extinction.

However, the abrupt cold spell that followed the eruption would still have significantly impacted day-to-day life for Neanderthals and early humans in Europe. Black and colleagues point out that temperatures in Western Europe would have decreased by an average of 2 to 4 degrees Celsius during the year following the eruption. These unusual conditions, they write, may have directly influenced survival and day-to-day life for Neanderthals and anatomically modern humans alike, and emphasize the resilience of anatomically modern humans in the face of abrupt and adverse changes in the environment.

FEATURED ARTICLE
Campanian Ignimbrite volcanism, climate, and the final decline of the Neanderthals
Benjamin A. Black et al., University of California, Berkeley, California, USA. Published online ahead of print on 19 March 2015; http://dx.doi.org/10.1130/G36514.1.

Baylor Researcher Finds First-Ever Evidence of Climate Change of Northern China Region Dating Back Thousands of Years (Baylor Univ.)

China's Hunshandake Sandy Lands

China’s Hunshandake Sandy Lands (Courtesy of Steve Forman)

Feb. 16, 2015

By Tonya B. Lewis

Study Sheds Light on How Populations Respond and Adapt to Climate Change

WACO, Texas (Feb. 16, 2015) — Using a relatively new scientific dating technique, a Baylor University geologist and a team of international researchers were able to document—for the first time—a drastic climate change 4,200 years ago in northern China that affected vegetation and led to mass migration from the area.

Steve Forman, Ph.D., professor of geology in the College of Arts & Sciences, and researchers—using a dating technique called Optically Stimulated Luminescence—uncovered the first evidence of a severe decrease in precipitation on the freshwater lake system in China’s Hunshandake Sandy Lands. The impact of this extreme climate change led to desertification—or drying of the region—and the mass migration of northern China’s Neolithic cultures.

Their research findings appear in the January 2015 issue of the Proceedings of the National Academy of Sciences and are available online.

“With our unique scientific capabilities, we are able to assert with confidence that a quick change in climate drastically changed precipitation in this area, although, further study needs to be conducted to understand why this change occurred,” Forman said.

Between 2001 and 2014, the researchers investigated sediment sections throughout the Hunshandake and were able to determine that a sudden and irreversible shift in the monsoon system led to the abrupt drying of the Hunshandake resulting in complications for the population.

“This disruption of the water flow significantly impacted human activities in the region and limited water availability. The consequences of a rapid climatic shift on the Hunshandake herding and agricultural cultures were likely catastrophic,” Forman said.

He said these climatic changes and drying of the Hunshandake continue to adversely impact the current population today. The Hunshandake remains arid and even with massive rehabilitation efforts will unlikely regrow dense vegetation.

“This study has far-reaching implications for understanding how populations respond and adapt to drastic climate change,” Forman said.

Forman is the director of the Geoluminescence Dating Research Lab in the department of geology.

Study co-authors include: Xiaoping Yang, Ph.D., of the Chinese Academy of Sciences; Louis A. Scuderi, Ph.D., of the University of New Mexico; Xulong Wang, Ph.D., of Chinese Academy of Sciences; Louis J. Scuderi, Ph.D., of the University of Hawaii; Deguo Zhang, Ph.D., of the Chinese Academy of Sciences; Hongwei Li, Ph.D., of the Chinese Academy of Sciences; Qinghai Xu, Ph.D., of Hebei Normal University; Ruichang Wang, Ph.D., of the Chinese Academy of Social Sciences; Weiwen Huang, Ph.D., of the Institute of Vertebrate Paleontology and Paleoanthropology and Shixia Yang, Ph.D., of the Institute of Vertebrate Paleontology and Paleoanthropology.

The West without Water: What Can Past Droughts Tell Us About Tomorrow? (Origins)

vol. 8, issue 6 – march 2015

by  B. LYNN INGRAM

Editor’s Note:
Almost as soon as European settlers arrived in California they began advertising the place as the American Garden of Eden. And just as quickly people realized it was a garden with a very precarious water supply. Currently, California is in the middle of a years-long drought and the water crisis is threatening the region’s vital agricultural economy, not to mention the quality of life of its people, plants, and animals. This month B. Lynn Ingram, Professor of Geography and Earth & Planetary Science, examines how a deep historical account of California’s water patterns can help us plan for the future.


The state of California is beginning its fourth year of a serious drought, with no end in sight.

The majority of water in the western United States is delivered by winter storms from the Pacific, and over the past year, those storms were largely blocked by an enormous ridge of high pressure. A relatively wet December has given way to the driest January on record, and currently over 90 percent of California is in severe to exceptional drought.

The southwestern states are also experiencing moderate to severe drought, and this comes on the heels of a very dry decade. This long drought has crept up on the region, partly because droughts encroach slowly and they lack the visual and visceral effects of other, more immediate natural disasters such as earthquakes, floods, or tsunamis.

Meteorologists define drought as an abnormally long period of insufficient rainfall adversely affecting growing or living conditions. But this bland definition belies the devastation wrought by these natural disasters. Drought can lead to failed crops, desiccated landscapes, wildfires, dehydrated livestock, and in severe cases, water wars, famine, and mass migration.

Although the situation in the West has not yet reached such epic proportions, the fear is that if it continues much longer, it could.

Lake Powell, in 2009, showing a white calcium carbonate “bathtub ring” exposed after a decade of drought lowered the level of the reservoir to 60 percent of its capacity. (Photo courtesy of U.S. Bureau of Reclamation.)

In California, reservoirs are currently at only 38 percent of capacity, and the snowpack is only 25 percent of normal for late January. Elsewhere in the Southwest, Lake Powell, the largest reservoir on the Colorado River, is at 44 percent of capacity.

The amount of water transported through irrigation systems to California’s Central Valley—the most productive agricultural region in the world—has been reduced to only 20 percent of customary quantities, forcing farmers to deepen groundwater wells and drill new ones.

Over the past year, 410,000 acres have been fallowed in this vast agricultural region that provides 30 percent of all the produce grown in the United States and virtually all of the world’s almonds, walnuts, and pistachios. As California dries up, food prices might well rise across the nation.

The question on everyone’s mind is when will this dry period finally come to an end and rainfall return to normal—and just what is normal for the U.S. Southwest when it comes to rain?

And with a growing and more urban population and an ever-changing climate, will we ever be free from the threat of long dry periods, with their disruptive effects on food production and the plants and animals that rely on water to survive?

A glance into the history of the Southwest reminds us that the climate and rainfall patterns have varied tremendously over time, with stretches of drought many decades longer than the one we are experiencing now.

Long dry stretches during the Medieval centuries (especially between 900 and 1350 CE) had dramatic effects on the native peoples of the Southwest (the ancestral Pueblo, Hohokam, and Sinagua), including civilizational collapse, violence, malnutrition, and forced social dislocation.

These earlier Americans are a warning to us.

The past 150 years, which we have used as our baseline for assumptions about rainfall patterns, water availability for agriculture, water laws, and infrastructure planning, may in fact be an unusually wet period.

Let’s look at the past few hundred years first and then explore the region’s climate in geological time.

Recent Droughts and the Arid Regions of the United States

John Wesley Powell stands as one of the most extraordinary scientists and explorers in America in the second half of the 19th century.

In 1869 he became the first white man to lead an expedition down the Colorado River and through the Grand Canyon, a feat all the more remarkable considering Powell had lost most of his right arm during the Civil War.

Ten years later, Powell published Report on the Lands of the Arid Regions of the United States, a careful assessment of the region’s capacity to be developed.

In it, Powell argued that very little of the West could sustain agriculture. In fact, his calculations suggested that even if all the water in western streams were harnessed, only a tiny fraction of the land could be irrigated.

Further, Powell believed that growth and development ought to be carefully planned and managed, and that boundaries drawn for new western states ought to follow watersheds to avoid inter-state fighting over precious water resources.

When Powell presented his findings to Congress, politicians howled. Powell found himself denounced by pro-development forces, including railroads and agricultural interests.

Prescient as Powell’s study has proved to be, it was almost entirely ignored at the time.

Instead, those development boosters responded to Powell’s data about the aridity of the west with a novel climatological theory: “Rain follows the plow.” They insisted that agriculture could cause the rains to fall, so like magic the more acres brought under cultivation the more rain farmers would enjoy.

The years surrounding the turn of the 20th century turned out to be unusually wet across much of the region. Hopeful pioneers continued to flock to the West, despite the visible signs of aridity.

They still do. The past century and a half in California and the West has been a period of steady population growth. And today the U.S. Southwest is the fastest-growing region in the United States (which itself is the world’s fourth-fastest-growing nation).

The Dirty Thirties and Beyond

The relatively wet period of the late nineteenth and early twentieth centuries gave way to drought in the late 1920s with the start of the Dust Bowl—now considered to be the United States’ worst climate tragedy.

The years between 1928 and 1939 were among the driest of the 20th century in the American West. This drought had particularly severe effects on California’s developing agricultural industry that were only mitigated by the extensive pumping of groundwater that eventually caused the ground surface in California’s Central Valley to drop by several feet.

Donner Lake, Sierra Nevada Range, California (Photo taken by B. Lynn Ingram).

In the 20th century, the single driest year (rivaling the 2013-2014 water year) was the drought of 1976-1977, extending across the entire state of California and into the Northwest, the Midwest, and the Canadian Prairie region north of Montana.

In California, precipitation levels dropped to less than a quarter of average. Reservoirs dropped to one-third their normal levels, and 7.5 million trees in the Sierra Nevada weakened by drought succumbed to insect related diseases, fueling massive wildfires. Snowfall was extremely sparse, forcing ski areas to close.

The following decade, another six-year drought occurred from 1987 to 1992, and while no single year was as severe as the drought of 1976-1977, the cumulative effects were ultimately more devastating. Annual precipitation attained only 50 percent of the 20th century average, with far-ranging impacts.

In the Sierra Nevada, water-stressed trees suffered widespread mortality from pine bark beetle infestations. Reduced stream flow caused major declines in fish populations, affecting commercial and recreational fisheries by lowering populations of Chinook salmon and striped bass.

By the fourth year of the drought, reservoir storage statewide was down 60 percent, causing a decline in hydroelectric power generation and the imposition of water restrictions including a decrease in agricultural water delivery by 75 percent.

Farmers relied more on groundwater, with private well owners deepening existing wells or drilling new ones. In the San Joaquin Valley, 11 million acre-feet more groundwater was extracted than could be replenished naturally, further lowering already low groundwater levels.

Measuring Droughts over Geological Time

As bad and worrisome as these more recent historical droughts in California and the West were, they pale in comparison to events uncovered in the geological record.

In recent years, earth scientists have been discovering that the climate and weather in the West over the past 100 to 150 years represents only a narrow part of the full range of climate in the region.

By peering deeper into Earth’s history—the past centuries and millennia—the frequency and magnitude of extreme climate events like drought can be better understood.

The evidence comes in various forms, such as mud from the bottom of lakes and ponds, microscopic organisms living in the oceans, bubbles frozen in glaciers, pencil-thin wood cores drilled from trees, and salts precipitating in dried-up lake bottoms.

A cut section of a Giant Sequoia trunk from Tuolumne Grove, Yosemite National Park, California, showing AD dates of fires (photo courtesy of Thomas Swetnam, Laboratory of Tree-Ring Research, University of Arizona).

One of the earliest records of past climate change comes from the rings of the long-lived Douglas fir. Trees are particularly effective recorders of climate because they respond every year to conditions of temperature and precipitation, responses recorded in the growth rings of their trunks.

In a landmark study during the early 1940s, a 600-year record of Colorado River flow using Douglas firs revealed several sustained periods of low water flow and these periods recurred with some regularity.

The reconstruction showed a particularly severe drought in the late 1500s, a drought lasting over a decade that has since shown up in multiple records from throughout the West.

These records also reveal that the driest single year over the past millennium (even drier than the parched 1976-1977 drought) occurred in 1580 CE. Trees across the West either had a narrow ring, or even a missing ring, that year.

Looking at an even broader picture, evidence from the past 10 millennia—a relatively warm era since the last Ice Age, which we call the Holocene—informs us that the severity of past extreme events (including droughts and floods) far exceeds those experienced over the past century and a half.

One of the longest dry periods for California and the West occurred during what is known as the mid-Holocene climatic optimum, a time when much of the earth experienced warmer than average conditions from about 4,500 to 7,500 years ago.

In the American West, there are numerous clues showing that this time period was drier than average for upwards of 1,400 years. These climate extremes caused significant human dislocations and forced native populations to migrate from the desert interiors of the West to the coastal regions.

The Tools for Uncovering Climate History

One of the most vivid clues for understanding the patterns of past drought in the West was revealed in Lake Tahoe toward the end of the Great Dust Bowl of the mid-1930s. At that time, Tahoe’s water level dropped fourteen inches, exposing a mysterious clustering of tree stumps sticking up from the water’s surface along the lake’s southern shore.

These trees attracted the attention of Samuel Harding, an engineering Professor from the University of California, Berkeley. Harding discovered that the trees were large, with trunks as wide as three feet in diameter, and appeared to be firmly rooted in the lake bottom.

Harding reasoned that the trees had grown in this location for a long time to attain such sizes, and since they were now submerged in over twelve feet of water, he surmised that at some time in the past the lake level had been much lower.

Frances Malamud-Roam, B. Lynn Ingram, and Christina Brady coring a small oxbow lake in the Sacramento Valley, California. (Photo taken by Anders Noren, University of Minnesota, LaCore curator.)

After collecting cores through their trunks, he counted up to 150 rings, concluding that it was a dry spell of over a century that caused the lake level to drop, allowing the trees to grow along the former shoreline.

Harding had to wait two decades before he could date this drought, after the invention of radiocarbon dating in the 1950s. Radiocarbon measurements of the outermost rings of the tree stumps showed that these trees died approximately 4,800 years ago.

Decades later, more evidence emerged from Lake Tahoe during another of California’s droughts in the late 1980s, when the lake’s surface dropped again, exposing even more tree stumps.

This time, it was an archaeologist, Susan Lindstrom, who noticed the tops of trees sticking out of the water along Tahoe’s southern shore. Donning scuba gear, Lindstrom was able to find fifteen submerged tree stumps that had escaped Harding’s attention, some measuring up to three and a half feet in diameter.

The radiocarbon dates from this much larger population of trees refined and extended the boundaries of the mid-Holocene drought, moving the beginning to as early as 6,290 years ago, and the ending to 4,840 years ago.

These stumps, located deeper in the lake, showed that the lake level had dropped by even more than Harding originally thought – by more than 20 feet. Lindstrom and other researchers have since located tree stumps in more places around the shores of Lake Tahoe and in other Sierran lakes.

Sediment core taken by Frances Malamud-Roam and B. Lynn Ingram from beneath San Francisco Bay, California. (Photo taken by B. Lynn Ingram.)

Geologists have also discovered more evidence from sediment cores taken from beneath lakes revealing the wide extent of this drought—across California and the Great Basin.

The archaeological records show that native populations migrated from the inland desert regions to the California coast at this time, likely in search of water and other resources during this prolonged drought.

Another dry millennium began about 3,000 years after the mid-Holocene drought ended. Evidence for this prolonged drought was found throughout California and the West.

One study, conducted in my laboratory at UC Berkeley, examined sediments accumulating beneath the San Francisco Bay estuary. These sediments contain information about precipitation over the entire drainage basin of the Sacramento and San Joaquin Rivers—an area that covers 40 percent of California.

Frances Malamud-Roam and Anders Noren coring marsh sediments adjacent to San Francisco Bay (Photo taken by B. Lynn Ingram)

Rivers draining the Sierra Nevada Range and Central Valley flow through San Francisco Bay and out the Golden Gate to the Pacific Ocean. In the Bay, fresh river water meets and mixes with the incoming ocean water, producing a range of salinity: fresh at the Delta, saline in the Central bay near the Golden Gate, and brackish in between.

Organisms growing in the Bay record the salinity in their shells, which then sink to the bottom and are preserved in the sediments. We took sediment cores from beneath the Bay and analyzed the chemistry of the fossil shells, allowing us to reconstruct past salinity, and therefore past river flow.

These studies showed that droughts lasting over a decade occurred regularly over the past two millennia, at intervals of 50 to 90 years. The cores also revealed a period of high salinity that began about 1,700 years ago and ending about 700 years ago, suggesting another prolonged drought.

We conducted a related study with Professor Roger Byrne in the Geography Department at UC Berkeley, coring the tidal marshlands surrounding the bay to assess the impact of this drought on this ecosystem.

These marshes have grown up around the edges of San Francisco Bay for the past 5,000 years or so, forming peat. The marsh peats contain fossil plants and chemical evidence for past periods of wetter and drier conditions in the watershed.

A drought in the watershed, if prolonged and severe, can cause higher salinity downstream in the estuary as the inflow of fresh water drops. In response, salt-tolerant species in the marshes expand further inland toward the Delta and the fresh water species retreat. Conversely, unusually wet winters generate fresher conditions in the estuary, leading to an expansion of freshwater-adapted species.

We analyzed the pollen and plant remains, carbon chemistry of the peats, and diatoms—the microscopic phytoplankton that grow in the marshes and produce tiny silica shells.

All of this evidence showed that the average freshwater inflow to San Francisco Bay was significantly lower than today’s levels for a thousand years, between 1,750 and 750 years ago.

The peak of this low-inflow interval, with freshwater flows 40 percent below average levels, occurred approximately 900 to 1,200 years ago, during a time when global temperatures were high, known as the Medieval Warm Period.

Mono Lake, showing calcium carbonate “tufa tower” formations that originally formed beneath the lake but are now exposed after the water level dropped. The eastern flank of the Sierra Nevada range is shown in the background. (Photo by D. J. DePaolo.)

Evidence for this drought was also discovered in an ancient lake situated east of the Sierra Nevada. Geography Professor Scott Stine analyzed the sedimentary sequences in Mono Lake, delineating patterns of alternately higher and lower lake levels for the past 4,000 years.

Mono Lake experienced an extended low stand that began about 1,600 years ago, dropping to an even lower level 700 to 1,200 years ago. During the 1980s drought, Stine also discovered large tree stumps submerged in Mono Lake.

Much like the tree stumps discovered in Lake Tahoe, these submerged trees indicated that at one time the lake was so small that its shoreline was several tens of feet lower than the present shoreline, when the trees now underwater could grow on dry ground. Stine went on to discover similar submerged tree stumps in lakes, marshes, and rivers throughout the central and southern Sierra Nevada Range.

By counting their growth rings, Stine determined that they had lived up to 160 years. Based on the amount the lake level dropped, he calculated that the average annual river flows in the region were only 40 to 60 percent of what they were in the late 20th century.

Radiocarbon dates of the outer growth layers of these tree stumps revealed that these trees clustered around two distinct periods, now known as the “Medieval Megadroughts”: CE 900 to 1100 and CE 1200 to 1350.

An ancient tree stump submerged in the West Walker River, eastern Sierra Nevada. (Photo courtesy of D. J. DePaolo.)

Across North America, tree-ring studies indicate that climate conditions over the past two millennia became steadily more variable (shifting between drier and wetter periods), with especially severe droughts between CE 900 and 1400.

These records show that over half the American West suffered severe drought between CE 1021 and CE 1051, and from CE 1130-1170, CE1240-1265 and CE 1360-1382.

The warm and dry conditions of the Medieval period spawned larger and more frequent wildfires, as recorded in the trunks of Giant sequoias—the massive redwoods growing in about 75 distinct groves along the mid-elevations of the western Sierra Nevada. These spectacular trees can live up to 3,200 years or more, and have exceeded 250 feet in height and 35 feet in diameter.

Thomas Swetnam, the current Director of the Laboratory of Tree Ring Research at the University of Arizona, discovered that the trees carry scars on their annual growth rings that indicate past fires in the region.

Swetnam sampled giant sequoias from five groves between Yosemite National Park and Sequoia National Park, far enough apart that individual fires could not have spread from one grove to the next. He dated the trees using ring-width patterns, and recorded the fire scars contained within annual rings.

His analysis reveals that during the Medieval period, from 1,200 to 700 years ago, an average of thirty-six fires burned every century.

During the centuries preceding the Medieval period (from about 1,500 to 1,200 years ago) and immediately following it (from about 700 years ago to the current century), the fire frequency was substantially lower, with an average of 21 fires per century.

The Human Costs of Droughts Then and Now

The archaeological record suggests that the extended periods of drought in the Medieval era caused severe hardship for both coastal and inland peoples— particularly the ancestral Pueblo communities—as dwindling resources increased disease, malnutrition, and warfare. Long inhabited sites were abandoned as the desperate populations wandered in search of new water sources.

Ancient pueblo cliff dwelling at Mesa Verde, southwestern Colorado. (Photo taken by B. Lynn Ingram)

Much of what archaeologists know about the ancestral Pueblo comes from pueblo and cliff dwellings from the four corners region, including Chaco Canyon in northwestern New Mexico, Mesa Verde in southwestern Colorado, and Canyon de Chelly in northeastern Arizona.

Chaco Canyon in New Mexico was the site of one of the most extensive of the ancestral Pueblo settlements. At its peak, during the 11th and early 12th centuries CE, Chaco Canyon had great pueblos the size of apartment blocks housing hundreds of residents in large, high-ceilinged rooms.

These settlements were supported by agriculture, allowing people to settle in one place year-round. Most of the farming depended on annual rains, supplemented by water from nearby streams and groundwater.

But over time, the climate became increasingly arid and unpredictable. The ancestral Pueblo farmers were forced to build an extensive system of diversion dams and canals, directing rainwater from the mesa tops to fields on the canyon floor, allowing them to expand the area of arable land.

The population in the four corners region swelled throughout the 11th and 12th centuries CE—but then collapsed.

Another ancient society, the Hohokam, lived in central Arizona near the confluence of Arizona’s only three rivers, the Gila, Verde, and Salt. The Hohokam civilization thrived in central Arizona for a thousand years, building an extensive network of integrated canal systems, capable of transporting large volumes of water long distances.

At their peak, an estimated 40,000 Hohokam lived in Arizona, but they suddenly vanished in the mid-15th century.

Montezuma’s Castle, a cliff dwelling occupied by the Sinagua, located just north of Camp Verde in central Arizona. (Photo by B. Lynn Ingram.)

In northern Arizona, between Phoenix and Flagstaff, the Sinagua culture also thrived during this period. As the climate turned drier, they built cliff dwellings in central Arizona, suggesting that resources became scarce, forcing them to build fortified dwellings with hidden food storage areas. The Sinagua also disappeared about the same time as the Hohokam.

All of these societies were flourishing prior to a rather abrupt collapse. The archaeological record of the last decades of the ancestral Pueblo in Chaco Canyon abounds with signs of suffering.

Skeletal remains show signs of malnutrition, starvation and disease; life spans declined and infant mortality rates increased. Evidence of violence, possibly warfare, was found in mass graves containing bones penetrated with arrowheads and teeth marks, and skulls bearing the scars of scalping.

Piles of belongings were found, apparently left behind as the people abandoned their settlements and fled, some to live in fortified hideouts carved in the cliff faces, protecting their hoarded food from enemies.

The unusually dry climate of the Medieval period also appeared to have tested the endurance and coping strategies of even the well-adapted native populations in California.

The skeletal remains show that life in the interior of California was particularly difficult, as the drought severely reduced sources of food (nuts, plants, deer, and other game). Settlements along rivers were abandoned, and trade between inland and coastal groups broke down. As water supplies dried up, conflicts – even battles – between groups arose over territory and food and water resources.

The Watery Lessons of the Past

The “Medieval Drought” serves as a model for what can happen in the West. It also provides an important impetus for water sustainability planning. And the hardships suffered by the first human inhabitants in the West provide important lessons.

For instance, during extended periods of abundant moisture, some societies experienced rapid population growth, leaving them vulnerable to collapse when the climate inevitably turned dry again.

Modern societies in the West have followed a similar path over the past century— after a century of fairly abundant moisture, the population in this region has exploded (and become more urbanized).

Modern engineering has allowed the exploitation of all available water sources for human use, and western water policy has favored water development for power, cities, and farms over sustainability of the environment and ecosystems.

These policies have allowed populations to grow to the limit that this region can support, leaving us vulnerable during extended drier conditions.

The longest six-year droughts experienced by the West over the past century are meager by comparison, despite the extreme hardship they brought to the region.

In fact, in the context of the longer-term climate history, the 20th century actually stands out as one of the wettest over the past 1,300 years, yet the droughts of the mid-1920s, 1977 and the late 1980s caused immense hardship for our society, based as it is upon heavy water usage.

In addition, future changes in the global climate will interact with the natural cycles of drought in California and the West in ways that are difficult to predict. Climate models predict that warming will likely make the extreme events, particularly floods and droughts, even larger and more frequent.

Some of these impacts have already begun. Over the past two decades, warming and an earlier start of the spring season have caused forest fires to become more frequent and intense.

A warmer climate will also bring less precipitation that falls as snow. The American West depends on snow-bearing winter storms for a natural water reservoir. This snow begins melting in the late spring, and continues into the summer, filling streams, lakes, and reservoirs that sustain natural ecosystems throughout the dry summer months.

The snow pack supports cities and irrigated agriculture, providing up to 80 percent of the year’s water supply across the West. As the region warms, the snow that does fall will melt faster and earlier in the spring, rather than melting during the late spring and summer, when it is so critically needed.

The message of past climates is that the range of “normal” climate is enormous—and we have experienced only a relatively benign portion of it in recent history. The region’s climate over the past decade has been dry when compared to the 20th century average, suggesting a return to a drier period.

This past year was also the warmest on record in the American West, and the ten hottest years on record occurred since 1997. The position of inhabitants of the West is precarious now and growing more so.

As we continue with an unsustainable pattern of water use, we become more vulnerable each year to a future we cannot control. It is time for policy makers in the West to begin taking action toward preparing for drier conditions and decreased water availability.


Read more from Origins on Water and the Environment: The World Water CrisisThe River JordanWho Owns the Nile?The Changing ArcticOver-Fishing in American WatersClimate Change and Human Population; and the Global Food Crisis.


Suggested Reading

Benson, L., Kashgarian, M., Rye, R., Lund, S., Paillet, F., Smoot, J., Kester, C., Mensing, S., Meko, D. and Lindstrom, S., 2002. “Holocene Multidecadal and Multi-centennial Droughts Affecting Northern California and Nevada.” Quaternary Science Reviews 21, 659-682.

Bradley, R.S., Briffa, K.R., Cole, J., Hughes, M.K., and Osborn, T.J., 2003. “The climate of the last millennium.” In: Alverson, K, Bradley, R.S., and Pedersen, T.F. (Eds.), Paleoclimate, Global Change and the Future, Springer Verlag, Berlin, pp. 105-49.

Brunelle, A. and Anderson, R.S., 2003. “Sedimentary charcoal as an indicator of late-Holocene drought in the Sierra Nevada, California, and its relevance to the future. “ The Holocene 13(1), 21-28.

Cayan, D. R., S. A. Kammerdiener, M. D. Dettinger, J. M. Caprio, and D. H. Peterson, 2001. “Changes in the onset of spring in the Western United States.” Bull. Am. Met. Soc., 82, 399-415.

Fagan, B., 2003. Before California: an Archaeologist Looks at Our Earliest Inhabitants. Rowman and Littlefield Publishers, Inc, Lanham, MD. 400 p.

Gleick, P.H. and E.L. Chalecki. 1999.” The impacts of climatic changes for water resources of the Colorado and Sacramento-San Joaquin river basins.” Journal of the American Water Resources Association, Vol. 35, No. 6, pp.

Hughes, M.K. and Brown, P.M., 1992. “Drought frequency in central California since 101 B.C. recorded in giant sequoia tree rings.” Climate Dynamics 6,161-197

Ingram, B. Lynn and Malamud-Roam, F. (2013) The West without Water: What past floods, droughts, and other climatic clues tell us about tomorrow. UC Press, 256 pages.

Ingram, B. L., Conrad, M.E., and Ingle, J.C., 1996. “A 2000-yr record of Sacramento-San Joaquin River inflow to San Francisco Bay estuary, California.” Geology 24, 331-334.

Lightfoot, K., 1997. “Cultural construction of coastal landscapes: A middle Holocene perspective from San Francisco Bay.” In: Erlandson, J. and Glassow, M. (eds), Archaeology of the California Coast during the Middle Holocene, 129-141. Series, Perspectives in California Archaeology 4, Institute of Archaeology, Univ. of California.

Malamud-Roam, F. and B.L. Ingram. 2004. “Late Holocene d13C and pollen records of paleosalinity from tidal marshes in the San Francisco estuary.” Quaternary Research 62, 134-145.

Stahle, D. W., Cook, E. R., Cleaveland, M. K., Therrell, M. D., Meko, D. M., Grissino-Mayer, H. D., Watson, E., and Luckman, B., 2000. “Tree-ring data document 16th century megadrought over North America.” EOS Transactions of the American Geophysical Union 81 (12), 121-125.

Stine, S., 1990. “Past Climate At Mono Lake.” Nature 345: 391.

Stine, S., 1994. “Extreme and persistent drought in California and Patagonia during mediaeval time.” Nature 369: 546-549.

Swetnam, T.W. 1993. “Fire history and climate change in Giant Sequoia groves.” Science 262, 885.

Do we need “the Anthropocene?” (Inhabiting the Anthropocene)

Zev Trachtenberg | January 5, 2015 at 7:00 am

As 2014 came to a close I received a wonderfully provocative e-mail from my friend and colleague in the Environmental Political Theory community John Meyer. He wrote that he has been led to

ask — out loud — a question that may seem either naive or cynical, but is not meant as either: so what’s the big deal about the Anthropocene? . . . To be clear, I get why it’s a big deal in geological terms. But what I’m wondering is: in what ways does it alter our understanding/approach/argument as philosophers, political theorists, political ecologists, environmental humanists, etc., that have already been working on environmental/sustainability concerns?

Does it add to or modify established critiques of “nature”? Does it convey an urgency that might otherwise be lacking? Does it alter our sense of human/more-than-human relations? Is it primarily a vehicle that might convey a set of concerns to a broader public? I know that none of these questions are original, but I pose them b/c I’m fascinated with the explosion of attention to the concept over the past couple years and yet genuinely struggling to make sense of the impetus/es for it.

This strikes me as a really good question. So as 2015 begins, here are some (I hope) seasonally appropriate reflections–not direct answers to John–on whether speaking about the Anthropocene adds some distinctive value to preexisting conversations about anthropogenic environmental change.

An immediate issue has to do with the status of the word as a term in Geology; in that context of course the Anthropocene is a proposed period in the geological time-scale, and it is an open question as to whether or not it will be formally adopted by the International Commission on Stratigraphy (the “ICS”—the decision is anticipated in 2016; here is the website for the working group handling the proposal). But the “explosion of attention” John mentions is due to the usage of the term in an informal way to refer to the massive transformation of Earth systems by human beings. Reference to the Anthropocene lends a kind of scientific prestige; it may be that work in the Humanities (my own area) is particularly prone to the urge to bolster its relevance and credibility by affiliating itself with a scientific endorsement of the project of discussing human-induced environmental change. And that appeal (made explicitly or implicitly) to Geology seems to vindicate the sense that anthropogenic change is really happening.

There is, no doubt, a degree of “wow factor” to the idea that humanity has become a force of nature, akin to geological phenomena like volcanoes and earthquakes, and potentially just as cataclysmic. Reference to the Anthropocene seems to ground this amazing thought in the sober authority of dispassionate geologists attuned to processes that shape the Earth itself. To speak of the Anthropocene is thus to hitch one’s claims to a fundamental understanding of nature, which can help justify one’s own demands on one’s audience for belief, and for action. It is not impossible, therefore, that we are experiencing a bandwagon effect–that the term “Anthropocene” is functioning as a buzzword in what will turn out to be a passing wave of academic fashion. Its passage might be accelerated if people find that, after all, adding the term to studies of particular examples of anthropogenic environmental change does not in fact add any value. And I can’t help but wonder what would happen if the ICS ends up rejecting the term next year. Will that deflate an academic bubble? Or will there be an intensification of C.P. Snow’s split between two cultures?

My own sense is that the “buzzier” sense of “Anthropocene” in fact does have some value—though I want to acknowledge that it is probably not be the best word for the job I want to approve. As a geological term “Anthropocene” refers to a hypothesized condition or set of facts about the Earth; it is the task of the ICS to decide whether that hypothesis is, in it sbest scientific judgment, true. But the informal usage of the word seems to connote a meaning over and above the idea that the present condition of the Earth has been profoundly shaped by human activity. On this additional meaning the word refers not to a condition, but to a broad intellectual approach. In this sense “Anthropocene” can be taken to name something like a paradigm: an intellectual framework which provides a consistent way for understanding diverse phenomena. The framework brings together a range of ideas and outlooks which harmonize around the theme that human activity has led to a distinctive condition of the Earth; it might therefore be called “Anthropocenism.” Thankfully I’ve not see that word before—and hope never to again. But the absence of a viable name leaves the imprecise usage—of the name for the condition—in place as the label for the approach, i.e. for the cluster of views that overlap by attending to anthropogenic environmental change.

In other words, the recent “explosion of attention” to the Anthropocene John notices might reflect the emergence of a consensus across a fairly wide range of disciplines on how to think about the relationship between human beings and the physical environment. The concept may not add any new information to any given field—many of which have well established traditions of examining that relationship. But, by redescribing ideas that are already available it facilitates the recognition that disparate fields indeed address a common theme. The shared term holds out at least the potential that researchers with profoundly different interests can see in each other’s work ideas that can advance their own. At the risk of sounding Pollyannaish, I believe that the possibility that the Anthropocene proposal might facilitate disciplinary cross-fertilization means that the value it adds to existing work is not negligible.

What I’ve said so far is pretty general; I have not given much detail about the content of the “paradigm” I’ve suggested the term the Anthropocene should be taken to name. One hope for this blog is that that content might emerge out the readings we are presenting in our reading posts. But I will conclude with a highly compressed (and too general) statement of what I take to be the core notions.

As the name of an outlook, the Anthropocene articulates the idea that human beings are natural: human life is embedded in the natural world. I draw two key implications from this starting point. First, while it is a commonplace of environmental thinking that our embeddedness means that human beings are essentially dependent on the causal processes at work in natural world, embeddedness equally means that human actions have effects in the natural world; this fact is also essential to our status as natural beings. The causal continuity here points to a systemic understanding, whereby there is no clear conceptual distinction between human and natural domains. Second, the humancharacter of the causal processes by which human beings affect the world is associated with technology. An image from the beginning of Stanley Kubrick’s 2001 conveys my point here. The proto-human creature becomes human by using a tool—the bone it uses as a weapon. It then tosses the bone in the air, and we next see a space craft. But the human character of human causality is at the same time social—and technology can only be understood in terms of the social and economic structures and processes through which it is developed and deployed.

As a matter of shorthand I interpret the Anthropocene (in the precise sense of a condition of the Earth) as the consequence of these two implications of naturalism: the socially organized deployment of technology so amplifies and concentrates human causal power that human activity can redirect or disrupt planetary-scale Earth system processes, yielding a state of the system best characterized by reference to human influence. But I am suggesting that we also use the term Anthropocene in a less precise way, to point to something like a paradigm. In that sense it gathers together empirical research that describes and explains the socially and technologically mediated effects human beings have on the world. Within this paradigm the project of understanding observations involves interpreting them in terms of the traces of human causal influence they might reveal. And that is why, I believe, this paradigm can successfully link normative inquiries to descriptive ones. For, by attending centrally to the structure and dynamics of human causal power within the natural world, it keeps in clear focus the issue of moral responsibility.

Antropoceno, Capitaloceno, Cthulhuceno: o que caracteriza uma nova época? (ClimaCom)

28/10/2014

A proposta de formalização de uma nova época da Terra levanta questões sobre utilidade, responsabilidade e formas alternativas de narrar a história do mundo em que vivemos

Por Daniela Klebis

Os impactos das ações humanas sobre o planeta nos últimos 200 anos têm sido tão profundos que podem justificar a definição de nova época para a Terra, o Antropoceno. No último dia 17 de outubro, a Comissão Internacional sobre Estratigrafia (ICS, na sigla inglês), reuniu-se em Berlim para dar continuidade às discussões sobre a formalização dessa nova época terrena, cuja decisão final será votada somente em 2016. A despeito dos processos burocráticos, o termo já foi informalmente assimilado por filósofos, arqueólogos, historiadores, ambientalistas e cientistas do clima e, nesse meio, o debate segue, para além da reunião de evidências físicas, no sentido de compreender sua utilidade: estamos prontos para assumir a época dos humanos?

A história da Terra se divide em escalas de tempo geológicas, que são definidas pela ICS, com sede em Paris, na França. Essas escalas de tempo começam com grandes espaços de tempos chamados éons, que se dividem em eras (como a Mezozóica), e então em períodos (Jurássico, Neogeno),  épocas e por fim, em idades. Quem acenou pela primeira vez a necessidade de definir uma nova época, baseada nos impactos indeléveis das ações humanas sobre a paisagem terrestre foi o químico atmosférico Paul J. Crutzen, prêmio Nobel de química em 1995. Cutzen sugeriu o termo Antropoceno durante o encontro  do Programa Internacional de Geofera e Biosfera (IGBP, na sigla em inglês), no México, em 2000. O evento tinha por objetivo discutir os problemas do Holoceno, a época em que nos encontramos há cerca de 11700 anos,desde o fim da era glacial.

A hipótese sustentada pelos defensores da nova denominação baseia-se nas observações sobre as mudanças iniciadas pelo homem sobre o ambiente desde 1800, cujas evidências geológicas  possuem impacto a  longo prazo na história da Terra.  E quais são as evidências que podem justificar a adoção do termo Antropoceno?  “O que nós humanos mais fizemos nesses dois séculos foi criar coisas que não existiram pelos 4,5 bilhões de anos da história da Terra”, denuncia o geólogo Jan Zalasiewicz, presidente do grupo de trabalho sobre o Antropoceno da ICS, em colóquio em Sidney, na Autrália, em março deste ano.

antropoceno1

Minerais sintéticos, fibras de carbono, plásticos, concreto, são alguns exemplos de novos elementos criados pelo homem. O concreto, um material produzido pela mistura de cimento, areia, pedra e água, vem se espalhando na superfície de nosso planeta a uma velocidade de 2 bilhões de quilômetros por ano, conforme aponta o geólogo.  Abaixo da superfície, escavações em busca de minérios e petróleo já abriram mais de 50 milhões de quilômetros em buracos subterrâneos.

Além das mudanças físicas, a emissão exagerada de dióxido de carbono e outros gases de efeito estufa, resultantes da ação humana, provocam mudanças químicas na atmosfera, como aquecimento global, descongelamento de calotas polares e acifidificação dos oceanos. A biosfera é também analisada, já que mudanças resultantes da perda de habitats, atividades predatórias e invasão de especies também provocam mudanças na composição química e física dos ambientes.

As evidências do impacto da ação humana,que vêm sendo consistentemente apontadas em estudos climáticos, foram reforçadas pelo 5º. Relatório do Painel Intercontinental de Mudanças Climáticas (IPCC), publicado no início do ano, com um consenso de 97% dos cientistas. Mais recentemente, no dia 30 de setembro, um relatório publicado no publicado pela WWF (World Wildlife Fund, em inglês), em parceria com a Sociedade Zoológica de Londres, apontou ainda que, nos últimos 40 anos, 52% da população de animais vertebrados na Terra desapareceu. Ao mesmo tempo, os seres humanos dobraram em quantidade. “Estamos empurrando a biosfera para a sua 6ª. extinção em massa”, alerta Hans-Otto Pörtner, do Instituto Alfred Wegener de Pesquisa Marinha e Polar, em Bremerhaven, Alemanha, e co-autor do capítulo sobre ecossistema do relatório do IPCC publicado nesse ano. Pörtner refere-se às cinco grandes extinções em massa registradas nos últimos 540 milhões de anos, caracterizadas por palentólogos como períodos em que mais de 75% das espécies foram extintas do planeta em um curto intervalo geológico.

“Há 200 anos, a coisas começaram a mudar o suficiente para visivelmente impactar o planeta: a população cresceu, assim como as emissões de CO2”, destaca Zalasiwicz. Segundo ele, o uso de energia cresceu 90 vezes entre 1800 e 2010, e já queimamos cerca de 200 milhões de anos de fósseis, entre carvão, óleo e gás. “Os humanos correspondem a 1/3 de todos os vertebrados da terra. Mas a dominação sem precedentes sobre todos os outros seres vivos, faz dessa a er a humana”, conclui.

Eileen Crist pesquisadora do Departamento de Ciências e Tecnologia na Sociedade, no Virginia Tech, no EUA, desafia a escolha do termo, defendendo que o discurso do Antropoceno deixa de questionar a soberania humana para propor, ao contrário, abordagens tecnológicas que poderiam tornar o domínio humano sustentável. “Ao afirmar a centralidade do homem – tanto como uma força causal quanto como objeto de preocupação – o Antropoceno encolhe o espaço discursivo para desafiar a dominação da biosfera, oferecendo, ao invés disso, um campo técnico-científico para a sua racionalização e um apelo pragmático para nos resignarmos à sua atualidade”, argumenta a pesquidadora em um artigo publicado em 2013.

O Antropoceno, dessa forma, entrelaça uma série de temas na formatação de seu discurso, como, por exemplo, o aumento acelerado da população que chegará a superar os 10 bilhões de habitantes; o crescimento econômico e a cultura de consumo enquanto modelo social dominante; a tecnologia como destino inescapável e, ao mesmo tempo, salvação da vida humana na Terra; e, ainda, o pressuposto de que o impacto humano é natural e contingente da nossa condição de seres providos de inteligência superior. Crist aponta que esse discurso mascara a opção de racionalizar o regime totalitátio do humano no planeta. “Como discurso coeso, ele bloqueia formas alternativas de vida humana na Terra”, indica.

antropoceno2

Relacionalidade

Donna Haraway, professora emérita da Universidade da Califórina em Santa Cruz, EUA, comentou, em participação no Colóquio Os Mil Nomes de Gaia, em setembro, que essa discussão é um dos “modos de buscar palavras que soam muito grandes, porém, não são grandes o suficiente para compreender a continuidade e a precariedade de viver e morrer nessa Terra”. Haraway é também umas das críticas do termo Antropoceno. Segundo ela, o Antropoceno implica um homem individual, que se desenvolve, e desenvolve uma nova paisagem de mundo, estranho a todas as outras formas de vida: uma percepção equivocada de um ser que seria capaz existir sem se relacionar com o resto do planeta. “Devemos compreender que para ser um, devemos ser muitos. Nos tornamos com outros seres”, comenta.

Para Haraway, épreciso, problematizar essa percepção, e endereçar a responsabilidade pelas mudanças, que está justamente no sistema capitalista que criamos. Este sim tem impulsionado a exploração, pelos homens, da Terra: “A história inteira poderia ser Capitaloceno, e não Antropoceno”, diz. Tal percepção, de acordo com a filósofa, pemite-nos resistir ao senso inescapabilidade presente nesse discurso, como Crist mencionou acima. “Estamos cercados pelo perigo de assumir que tudo está acabado, que nada pode acontecer”, diz.

Haraway aponta, entretanto, que é necessário evocar um senso de continuidade (ongoingness,em inglês),a partir de outras possibilidades narrativas e de pensamento.Uma delas, seria o Cthulhuceno, criado pela filósofa. A expressão vem de um conto de H.P.Lovecraft, O chamado de Cthulhu, que fala sobre humanos que têm suas mentes deterioradas quando, em rituais ao deus Cthulhu – uma mistura de homem, dragão e polvo que vive adormecido sob as águas do Pacífico Sul – conseguem vislumbrar uma realidade diferente da que conheciam.  No início da história, o autor norte-americano descreve o seguinte: “A coisa mais misericordiosa do mundo, acho eu, é a incapacidade da mente humana de correlacionar tudo que ela contém”.  A partir desse contexto, Donna Haraway explica que é necessário “desestabilizar mundos de pensamentos, com mundos de pensamentos”. O Cthulhuceno não é sobre adotar uma transcendência, uma ideia de vida ou morte: “trata-se de abraçar a continuidade sinuosa do mundo terreno, no seu passado​​, presente e futuro. Entretanto, tal continuidade implica em assumir que existe um problema muito grande e que ele precisa ser enfrentado. Devemos lamentar o que aconteceu, pois não deveria ter ocorrido. Mas não temos que continuar no mesmo caminho”, sugere.

“Forum: Archaeology of the Anthropocene” (AAA Blog)

“Forum: Archaeology of the Anthropocene”

by Asa Randall

CITATION:

Edgeworth, M., Benjamin, J., Clarke, B., Crossland, Z., Domanska, E., Gorman, A. C., Graves-Brown, P., Harris, E. C., Hudson, M. J., Kelley, J. M., Paz, V. J., Salerno, M. A., Witmore, C. & Zarankin, A. 2014. Forum: Archaeology of the Anthropocene. Journal of Contemporary Archaeology, 1,1, pp. 73-132.

ON-LINE AVAILABILITY:

 DOI: 10.1558/jca.v1i1.73

ABSTRACT:

What role will archaeology play in the Anthropocene – the proposed new geological epoch marked by human impact on Earth systems? That is the question discussed by thirteen archaeologists and other scholars from five continents in this thought-provoking forum. Their responses are diverse and wide-ranging. While Edward Harris looks to archaeological stratigraphy for a material paradigm of the Anthropocene, Alice Gorman explores the extent of human impact on orbital space and lunar surfaces – challenging the assumption that the Anthropocene is confined to Earth. Jeff Benjamin investigates the sounds of the Anthropocene. Paul Graves-Brown questions the idea that the epoch had its onset with the invention of the steam engine, while Mark Hudson uses Timothy Morton’s concept of hyperobjects to imagine the dark artefacts of the future. Victor Paz doubts the practical relevance of the concept to archaeological chronologies, and Bruce Clarke warns archaeologists to steer clear of the Anthropocene altogether, on the grounds of the overbearing hubris of the very idea of the Age of Humans. Others like Jason Kelly and Ewa Domanska regard the Anthropocene debate as an opportunity to reach new forms of understanding of Earth systems. André Zarankin and Melisa Salerno ground significant issues in the archaeology of Antarctica. And Zoe Crossland explores the vital links between the known past and the imagined future. As a discipline orientated to the future and contemporary world as well as the past, Chris Witmore concludes, archaeology in the Anthropocene will have more work than it can handle.

The archaeological imagination is the ability to conceive of a past through encounters with old objects, substances, or places (Thomas, 1996, p. 63-64). In a sense, the archaeological imagination meshes the past with the present, as ancient objects are animated with contemporary concerns. Imagining a past and even empathizing with ancient actors likely has its roots in early modern humans (Gamble, 2008, p. 1-2). That is, everyone has an archaeological imagination.  Archaeologists in particular have spent a fair amount of time honing their scientific toolkits and theoretical frameworks to create informed narratives about the past. Much archaeological effort has been oriented towards elucidating patterns and processes in deep time, although archaeologies of modern rubbish disposal or ruination (e.g. Rathje and Murphy, 2001, p, Dawdy, 2010, p.) have coexisted with studies of the more ancient. Indeed, archaeology’s focus on the material world—or human entanglements with it—provides relevant viewpoint in which to engage with, critique, or document the Anthropocene.

In the inaugural issue of the Journal of Contemporary Archaeology, Edgeworth and colleagues turn their archaeological imagination towards the “anthropocene” and ask what does an archaeology of the Anthropocene look like, how do today’s practices create tangible (or even acoustic) traces, and what might the Anthropocene’s archaeological record look like in the future? The collection of short papers emerged from the 2013 Theoretical Archaeology Group meeting, and there is much to digest here. Of the contributions in the forum, those by Edgeworth (“Introduction”) and Witmore (“Archaeology, the Anthropocene, and the Hypanthropocene”) provide useful discussions of the themes, controversies, and contributions. Broadly speaking, the forum participants engage with the ways in which the Anthropocene destabilizes disciplinary boundaries and makes complex the relationship between time scales (human versus geological) and the spatial scale(s) of human activity in the world. These same sorts of themes echo ongoing debate regarding the Anthropocene as a precise “thing” whose identity is controlled by Geologists, or one that invokes or necessitates many viewpoints.

Of particular interest to me were those contributions that highlighted ways in which aspects of Anthropocenic habitation extend or unsettle traditional archaeological imaginations. For example, Hudson (“Dark Artifacts: Hyperobjects and the Archaeology of the Anthropocene”) considers from an archaeological perspective what Morton (2010, p.) refers to as “hyperobjects.” Paraphrasing Hudson, hyperobjects are characterized as massively distributed such that they are physically and conceptually viscous, of a particular phase but of great durability, nonlocal (i.e. not typical of any one place), formed from interactions, and often “dangerous”.  Cited examples include Styrofoam, radionuclides, or plastiglomerate (so, too, the rebounding landscapes described by Ingo Schlupp may qualify); the spatial distribution, small size, or virtual character of hyperobjects makes them difficult to visualize or even comprehend. Not only do hyperobjects resist easy interpretation due to their lack of being of a particular place, their durability means that they lack life-cycles that are intelligible within a human framework of hundreds or thousands of years (that is, they will co-exist with many different kinds of societies in the future). While hyperobjects are of human agency, they reside in a strange state between cultural and natural whose ubiquity does not neatly sit in the localized or humanized imagined pasts that we are accustomed to thinking through, and which may ultimately lead to indifference towards them.

In a related vein, Crossland (“Anthropocene: Locating Agency, Imagining the Future”) considers the ways in which narratives about the Anthropocene can warp time and agency. To paraphrase Crossland, by restricting the Anthropocene to the industrial era (replete with dangerous hyperobjects), a teological arrow is held fast between the past and the present, such that only a dystopic future is possible. On the other hand, relocating the Anthropocene to the ancient world (the so-called Paleoanthropocene) may promote continuity between present and past (and redistribute the responsibility for it globally), but “the power of the imagery is undercut, and the ability of the concept to shock people and governments into change seems to be weakened” (p. 125). Crossland suggests a third route for our archaeological imaginations in the Anthropocene, which is to accept that at any point in time futures are open ended, and that “traces of the past therefore provide the ground for imagining the future” (p. 127). While preexisting conditions are important, traces of the past are really collaborations between the past and the present. We can avoid historical narratives that are arranged as progressive change with dystopian futures by envisioning that presents (in the past and our own) had many potential futures.  Kenneth Sassaman (2012, p.) has similarly argued that the relationships between past/present/future are never stable, and that communities in the past likely planned for their own alternative futures.

I’m not certain that the concept of hyperobject does anything for us, particularly as a marker of the Anthropocene. It is likely that other “pre-modern” objects or technologies have been equally influential but we do not reflect on them either. Furthermore, the time and space bending properties of the archaeological imagination are not easily translated into a world dominated by progressive thinking.  But, Hudson and other papers in this contribution challenges us to think about how the categories of objects and substances we are creating today—and the methods we use to interrogate them—can influence how we think about time, culture, and even social justice. In this regard, I suspect the upcoming “Anthropocene Slam: A Cabinet of Curiosities” forum (which will apparently be streamed live) will provide much food for thought. According to the forum’s description, each contributor has provided an object of study, ranging from substances such as concrete to room thermostats, through which we might visualize or imagine the relations between pasts and futures and different ecologies.

What will a future archaeological imagination make of the anthropocene? Time will certainly tell.  Yet, perhaps thinking about how we are creating an archaeological record of our own may make us more keenly future oriented.

FURTHER READING:

Dawdy, S. L. 2010. Clockpunk Anthropology and the Ruins of Modernity. Current Anthropology, 51, 761-793. DOI 10.1086/657626. Dawdy explores the ways in which creative uses of  and experiences with the past in contemporary times undermines easy separations between modern and premodern.

Gamble, C. 2008. Archaeology: the basics, New York, Routledge. This is an easy to read introductory text on Archaeology and interpretation.

Morton, T. 2010. The ecological thought, Cambridge, Mass., Harvard University Press. Morton considers what interconnectedness means, particularly when we acknowledge that all things have relations.

Rathje, W. L. & Murphy, C. 2001. Rubbish!: the archaeology of garbage, Tucson, AZ, University of Arizona Press. This popular book provides insights from archaeological examinations of modern refuse disposal practices.

Sassaman, K. E. 2012. Futurologists Look Back. Archaeologies, 10.1007/s11759-012-9205-0, 1–19. 10.1007/s11759-012-9205-0. Sassaman argues that the wall that is often erected between modern and premodern communities is minimized if we allow ancient communities to have imagined and acted upon their own futures (so called futures past).

Thomas, J. 1996. Time, Culture and Identity: An Interpretive Archaeology, London, Routledge. Thomas introduces the concept of the archaeological imagination.

Megafloods: What They Leave Behind (Science Daily)

Jan. 16, 2014 — South-central Idaho and the surface of Mars have an interesting geological feature in common: amphitheater-headed canyons. These U-shaped canyons with tall vertical headwalls are found near the Snake River in Idaho as well as on the surface of Mars, according to photographs taken by satellites. Various explanations for how these canyons formed have been offered — some for Mars, some for Idaho, some for both — but in a paper published the week of December 16 in the online issue ofProceedings of the National Academy of Sciences,Caltech professor of geology Michael P. Lamb, Benjamin Mackey, formerly a postdoctoral fellow at Caltech, and W. M. Keck Foundation Professor of Geochemistry Kenneth A. Farley offer a plausible account that all these canyons were created by enormous floods.

Stubby Canyon, Malad Gorge State Park, Idaho. (Credit: Michael Lamb)

Canyons in Malad Gorge State Park, Idaho, are carved into a relatively flat plain composed of a type of volcanic rock known as basalt. The basalt originated from a hotspot, located in what is now Yellowstone Park, which has been active for the last few million years. Two canyons in Malad Gorge, Woody’s Cove and Stubby Canyon, are characterized by tall vertical headwalls, roughly 150 feet high, that curve around to form an amphitheater. Other amphitheater-headed canyons can be found nearby, outside the Gorge — Box Canyon, Blue Lakes Canyon, and Devil’s Corral — and also elsewhere on Earth, such as in Iceland.

To figure out how they formed, Lamb and Mackey conducted field surveys and collected rock samples from Woody’s Cove, Stubby Canyon, and a third canyon in Malad Gorge, known as Pointed Canyon. As its name indicates, Pointed Canyon ends not in an amphitheater but in a point, as it progressively narrows in the upstream direction toward the plateau at an average 7 percent grade. Through Pointed Canyon flows the Wood River, a tributary of the larger Snake River, which in turn empties into the Columbia River on its way to the Pacific Ocean.

Geologists have a good understanding of how the rocks in Woody’s Cove and Stubby Canyon achieved their characteristic appearance. The lava flows that hardened into basalt were initially laid down in layers, some more than six feet thick. As the lava cooled, it contracted and cracked, just as mud does when it dries. This produced vertical cracks across the entire layer of lava-turned-basalt. As each additional sheet of lava covered the same land, it too cooled and cracked vertically, leaving a wall that, when exposed, looks like stacks of tall blocks, slightly offset from one another with each additional layer. This type of structure is called columnar basalt.

While the formation of columnar basalt is well understood, it is not clear how, at Woody’s Cove and Stubby Canyon, the vertical walls became exposed or how they took on their curved shapes. The conventional explanation is that the canyons were formed via a process called “groundwater sapping,” in which springs at the bottom of the canyon gradually carve tunnels at the base of the rock wall until this undercutting destabilizes the structure so much that blocks or columns of basalt fall off from above, creating the amphitheater below.

This explanation has not been corroborated by the Caltech team’s observations, for two reasons. First, there is no evidence of undercutting, even though there are existing springs at the base of Woody’s Cove and Stubby Canyon. Second, undercutting should leave large boulders in place at the foot of the canyon, at least until they are dissolved or carried away by groundwater. “These blocks are too big to move by spring flow, and there’s not enough time for the groundwater to have dissolved them away,” Lamb explains, “which means that large floods are needed to move them out. To make a canyon, you have to erode the canyon headwall, and you also have to evacuate the material that collapses in.”

That leaves waterfall erosion during a large flood event as the only remaining candidate for the canyon formation that occurred in Malad Gorge, the Caltech team concludes.

No water flows over the top of Woody’s Cove and Stubby Canyon today. But even a single incident of overland water flow occurring during an unusually large flood event could pluck away and topple boulders from the columnar basalt, taking advantage of the vertical fracturing already present in the volcanic rock. A flood of this magnitude could also carry boulders downstream, leaving behind the amphitheater canyons we see today without massive boulder piles at their bottoms and with no existing watercourses.

Additional evidence that at some point in the past water flowed over the plateaus near Woody’s Cove and Stubby Canyon are the presence of scour marks on surface rocks on the plateau above the canyons. These scour marks are evidence of the type of abrasion that occurs when a water discharge containing sediment moves overland.

Taken together, the evidence from Malad Gorge, Lamb says, suggests that “amphitheater shapes might be diagnostic of very large-scale floods, which would imply much larger water discharges and much shorter flow durations than predicted by the previous groundwater theory.” Lamb points out that although groundwater sapping “is often assumed to explain the origin of amphitheater-headed canyons, there is no place on Earth where it has been demonstrated to work in columnar basalt.”

Closing the case on the canyons at Malad Gorge required one further bit of information: the ages of the rock samples. This was accomplished at Caltech’s Noble Gas Lab, run by Kenneth A. Farley, W. M. Keck Foundation Professor of Geochemistry and chair of the Division of Geological and Planetary Sciences.

The key to dating surface rocks on Earth is cosmic rays — very high-energy particles from space that regularly strike Earth. “Cosmic rays interact with the atmosphere and eventually with rocks at the surface, producing alternate versions of noble gas elements, or isotopes, called cosmogenic nuclides,” Lamb explains. “If we know the cosmic-ray flux, and we measure the accumulation of nuclides in a certain mineral, then we can calculate the time that rock has been sitting at Earth’s surface.”

At the Noble Gas Lab, Farley and Mackey determined that rock samples from the heads of Woody’s Cove and Stubby Canyon had been exposed for the same length of time, approximately 46,000 years. If Lamb and his colleagues are correct, this is when the flood event occurred that plucked the boulders off the canyon walls, leaving the amphitheaters behind.

Further evidence supporting the team’s theory can be found in Pointed Canyon. Rock samples collected along the walls of the first kilometer of the canyon show progressively more exposure in the downstream direction, suggesting that the canyon is still being carved by Wood River. Using the dates of exposure revealed in the rock samples, Lamb reconstructed the probable location of Pointed Canyon at the time of the formation of Woody’s Cove and Stubby Canyon. At that location, where the rock has been exposed approximately 46,000 years, the surrounding canyon walls form the characteristic U-shape of an amphitheater-headed canyon and then abruptly narrow into the point that forms the remainder of Pointed Canyon. “The same megaflood event that created Woody’s Cove and Stubby Canyon seems to have created Pointed Canyon,” Lamb concludes. “The only difference is that the other canyons had no continuing river action, while Pointed Canyon was cut relatively slowly over the last 46,000 years by the Wood River, which is not powerful enough to topple and pluck basalt blocks from the surrounding plateau, resulting in a narrow channel rather than tall vertical headwalls.”

Solving the puzzle of how amphitheater-headed canyons are created has implications reaching far beyond south-central Idaho because similar features — though some much larger — are also present on the surface of Mars. “A very popular interpretation for the amphitheater-headed canyons on Mars is that groundwater seeps out of cracks at the base of the canyon headwalls and that no water ever went over the top,” Lamb says. Judging from the evidence in Idaho, however, it seems more likely that on Mars, as on Earth, amphitheater-headed canyons were created by enormous flood events, suggesting that Mars was once a very watery planet.

Journal Reference:

  1. M. P. Lamb, B. H. Mackey, K. A. Farley. Amphitheater-headed canyons formed by megaflooding at Malad Gorge, IdahoProceedings of the National Academy of Sciences, 2013; 111 (1): 57 DOI: 10.1073/pnas.1312251111

Anthropocene Continues to Spark Scientific Debate (The Geological Society of America)

GSA Annual Meeting Technical Session: “Geomorphology of the Anthropocene”

Boulder, Colorado, USA – How have humans influenced Earth? Can geoscientists measure when human impacts began overtaking those of Earth’s other inhabitants and that of the natural Earth system? Responding to increasing scientific recognition that humans have become the foremost agent of change at Earth’s surface, organizers of this GSA technical session have brought together speakers and poster presentations from a variety of sources in order to answer these questions and define the “Geomorphology of the Anthropocene.”

“Anthropocene” is a fairly new term (first used ca. 2002 by Paul Crutzen) now being applied to the current global environment and its domination by human activity (see J. Zalasiewicz et al.’s 2008 GSA Today article “Are we now living in the Anthropocene” [v. 18, no. 2, p. 4]). This “era” or “epoch” spans a yet-undetermined but so far brief (in geologic terms) time scale potentially marking the end of the Holocene epoch.

Session organizers Anne Jefferson of Kent State University, Karl Wegmann of North Carolina State University, and Anne Chin of the University of Colorado Denver have gathered presentations addressing human interactions with Earth’s systems. Research studies span a range of temporal and spatial scales and investigate a variety of influences, including the effects of indigenous culture as well as dams and cities.

Chin says that part of the research is spurred by “the difficulty of finding any place (no matter how ‘pristine’) where the landscape hasn’t been affected by human activities.” She cites the U.S. National Research Council’s “Grand Challenge” in Landscapes on the Edge: New Horizons for Research on Earth’s Surface (2010) to determine how Earth’s surface may evolve in the Anthropocene.

Chin also points to the intensification of debate over “Anthropocene” and the time frame it encompasses as scientists, policymakers, the media, and the public become increasingly aware of the term. A goal of this session is to address the debate and add a greater base of scientific understanding to round out the popularity of the idea.

Three Geological Society of American (GSA) specialty divisions cosponsor this session: the GSA Quaternary Geology and Geomorphology Division, the GSA Geology and Society Division, and the GSA Archaeological Geology Division, thus bringing to bear a multidisciplinary perspective to the problem. Talks include “An early Anthropocene analog: Ancient Maya impacts on the Earth’s surface”; “Removing streams from the landscape: Counting the buried streams beneath urban landscapes”; and Anthropogenic influences on rates of coastal change.”

Papers from this session will be compiled into a special issue of Anthropocene, a new journal launching in 2013 by Elsevier, devoted to addressing one of the grand challenges of our time.

Session 8: T24. Geomorphology of the Anthropocene: The Surficial Legacy of Past and Present Human Activities
Talks: https://gsa.confex.com/gsa/2012AM/webprogram/Session30644.html
When: Sunday, 4 Nov., 8 a.m. to noon
Where: Charlotte Convention Center, Room 207A
Poster Session: https://gsa.confex.com/gsa/2012AM/webprogram/Session31925.html
When: Sunday, 4 Nov., 9 a.m. to 6:30 p.m.
Where: Charlotte Convention Center Hall B

Contacts: 
Anne J. Jefferson: ajeffer9@kent.edu, +1-980-213-5933
Karl W. Wegmann: kwwegman@ncsu.edu
Anne Chin: anne.chin@ucdenver.edu, +1-979-492-0074

Find out what else is new and newsworthy by browsing the complete technical program schedule at https://gsa.confex.com/gsa/2012AM/finalprogram/.

To identify presentations in specific areas of interest, search topical sessions by discipline categories or sponsors using the drop-down menus atwww.geosociety.org/meetings/2012/sessions/topical.asp, or use your browser’s “find” feature to search for keywords or convener names.

New Book Explores ‘Noah’s Flood’: Says Bible and Science Can Get Along (Science Daily)

ScienceDaily (Aug. 14, 2012) — David Montgomery is a geomorphologist, a geologist who studies changes to topography over time and how geological processes shape landscapes. He has seen firsthand evidence of how the forces that have shaped Earth run counter to some significant religious beliefs.

But the idea that scientific reason and religious faith are somehow at odds with each other, he said, “is, in my view, a false dichotomy.”

In a new book, “The Rocks Don’t Lie: A Geologist Investigates Noah’s Flood” (Aug. 27, 2012, W.W. Norton), Montgomery explores the long history of religious thinking — particularly among Christians — on matters of geological discovery, from the writings of St. Augustine 1,700 years ago to the rise in the mid-20th century of the most recent rendering of creationism.

“The purpose is not to tweak people of faith but to remind everyone about the long history in the faith community of respecting what we can learn from observing the world,” he said.

Many of the earliest geologists were clergy, he said. Nicolas Steno, considered the founder of modern geology, was a 17th century Roman Catholic priest who has achieved three of the four steps to being declared a saint in the church.

“Though there are notable conflicts between religion and science — the famous case of Galileo Galilei, for example — there also is a church tradition of working to reconcile biblical stories with known scientific fact,” Montgomery said.

“What we hear today as the ‘Christian’ positions are really just one slice of a really rich pie,” he said.

For nearly two centuries there has been overwhelming geological evidence that a global flood, as depicted in the story of Noah in the biblical book of Genesis, could not have happened. Not only is there not enough water in the Earth system to account for water levels above the highest mountaintop, but uniformly rising levels would not allow the water to have the erosive capabilities attributed to Noah’s Flood, Montgomery said.

Some rock formations millions of years old show no evidence of such large-scale water erosion. Montgomery is convinced any such flood must have been, at best, a regional event, perhaps a catastrophic deluge in Mesopotamia. There are, in fact, Mesopotamian stories with details very similar, but predating, the biblical story of Noah’s Flood.

“If your world is small enough, all floods are global,” he said.

Perhaps the greatest influence in prompting him to write “The Rocks Don’t Lie” was a 2002 expedition to the Tsangpo River on the Tibetan Plateau. In the fertile river valley he found evidence in sediment layers that a great lake had formed in the valley many centuries ago, not once but numerous times. Downstream he found evidence that a glacier on several occasions advanced far enough to block the river, creating the huge lake.

But ice makes an unstable dam, and over time the ice thinned and finally give way, unleashing a tremendous torrent of water down the deepest gorge in the world. It was only after piecing the story together from geological evidence that Montgomery learned that local oral traditions told of exactly this kind of great flood.

“To learn that the locals knew about it and talked about it for the last thousand years really jolted my thinking. Here was evidence that a folk tale might be reality based,” he said.

He has seen evidence of huge regional floods in the scablands of Eastern Washington, carved by torrents when glacial Lake Missoula breached its ice dam in Montana and raced across the landscape, and he found Native American stories that seem to tell of this catastrophic flood.

Other flood stories dating back to the early inhabitants of the Pacific Northwest and from various islands in the Pacific Ocean, for example, likely tell of inundation by tsunamis after large earthquakes.

But he noted that in some regions of the world — in Africa, for example — there are no flood stories in the oral traditions because there the annual floods help sustain life rather than bring destruction.

Floods are not always responsible for major geological features. Hiking a trail from the floor of the Grand Canyon to its rim, Montgomery saw unmistakable evidence of the canyon being carved over millions of years by the flow of the Colorado River, not by a global flood several thousand years ago as some people still believe.

He describes that hike in detail in “The Rocks Don’t Lie.” He also explores changes in the understanding of where fossils came from, how geologists read Earth history in layers of rock, and the writings of geologists and religious authorities through the centuries.

Montgomery hopes the book might increase science literacy. He noted that a 2001 National Science Foundation survey found that more than half of American adults didn’t realize that dinosaurs were extinct long before humans came along.

But he also would like to coax readers to make sense of the world through both what they believe and through what they can see for themselves, and to keep an open mind to new ideas.

“If you think you know everything, you’ll never learn anything,” he said.

New Understanding to Past Global Warming Events: Hyperthermal Events May Be Triggered by Warming (Science Daily)

These geological deposits make the Bighorn Basin area of Wyoming ideal for studying the PETM. (Credit: Aaron Diefendorf)

ScienceDaily (Apr. 2, 2012) — A series of global warming events called hyperthermals that occurred more than 50 million years ago had a similar origin to a much larger hyperthermal of the period, the Pelaeocene-Eocene Thermal Maximum (PETM), new research has found. The findings, published in Nature Geoscience online on April 1, 2012, represent a breakthrough in understanding the major “burp” of carbon, equivalent to burning the entire reservoir of fossil fuels on Earth, that occurred during the PETM.

“As geologists, it unnerves us that we don’t know where this huge amount of carbon released in the PETM comes from,” says Will Clyde, associate professor of Earth sciences at the University of New Hampshire and a co-author on the paper. “This is the first breakthrough we’ve had in a long time. It gives us a new understanding of the PETM.” The work confirms that the PETM was not a unique event – the result, perhaps, of a meteorite strike – but a natural part of Earth’s carbon cycle.

Working in the Bighorn Basin region of Wyoming, a 100-mile-wide area with a semi-arid climate and stratified rocks that make it ideal for studying the PETM, Clyde and lead author Hemmo Abels of Utrecht University in the Netherlands found the first evidence of the smaller hyperthermal events on land. Previously, the only evidence of such events were from marine records.

“By finding these smaller hyperthermal events in continental records, it secures their status as global events, not just an ocean process. It means they are atmospheric events,” Clyde says.

Their findings confirm that, like the smaller hyperthermals of the era that released carbon into the atmosphere, the release of carbon in the PETM had a similar origin. In addition, the warming-to-carbon release of the PETM and the other hyperthermals are similarly scaled, which the authors interpret as an indication of a similar mechanism of carbon release during all hyperthermals, including the PETM.

“It points toward the fact that we’re dealing with the same source of carbon,” Clyde says.

Working in two areas of the Bighorn Basin just east of Yellowstone National Park – Gilmore Hill and Upper Deer Creek – Clyde and Abels sampled rock and soil to measure carbon isotope records. They then compared these continental recordings of carbon release to equivalent marine records already in existence.

During the PETM, temperatures rose between five and seven degrees Celsius in approximately 10,000 years — “a geological instant,” Clyde calls it. This rise in temperature coincided exactly with a massive global change in mammals, as land bridges opened up connecting the continents. Prior to the PETM, North America had no primates, ancient horses, or split-hoofed mammals like deer or cows.

Scientists look to the PETM for clues about the current warming of Earth, although Clyde cautions that “Earth 50 million years ago was very different than it is today, so it’s not a perfect analog.” While scientists still don’t fully understand the causes of these hyperthermal events, “they seem to be triggered by warming,” Clyde says. It’s possible, he says, that less dramatic warming events destabilized these large amounts of carbon, releasing them into the atmosphere where they, in turn, warmed the Earth even more.

“This work indicates that there is some part of the carbon cycle that we don’t understand, and it could accentuate global warming,” Clyde says.