Arquivo da tag: Extinção animal

Human impact on nature ‘dates back millions of years’ (BBC)

Early human ancestors could have stolen food from other animals. Mauricio Antón

By Helen Briggs BBC News

20 January 2020

The impact of humans on nature has been far greater and longer-lasting than we could ever imagine, according to scientists.

Early human ancestors living millions of years ago may have triggered extinctions, even before our species evolved, a study suggests.

A decline in large mammals seen in Eastern Africa may have been due to early humans, researchers propose.

Extinction rates started to increase from around four million years ago.

This coincides with the period when ancient human populations were living in the area, as judged by fossil evidence.

“We are now negatively impacting the world and the species that live in it more than ever before. But this does not mean that we used to live in true harmony with nature in the past,” said study researcher, Dr Søren Faurby of the University of Gothenburg.

“We are extremely successful in monopolising resources today, and our results show that this may have also been the case with our ancestors.”

Getty Images. A lion feasts on the carcass of a rhinoceros in Kenya

The researchers looked at extinction rates of large and small carnivores and how this correlated with environmental changes such as rainfall and temperature.

They also looked at changes in the brain size of human ancestors such as Australopithecus and Ardipithecus.

They found that extinction rates in large carnivores correlated with increased brain size of human ancestors and with vegetation changes, but not with precipitation or temperature changes.

They found the best explanation for carnivore extinction in East Africa was that these animals were in direct competition for food with our ancestors.

They think human ancestors may have stolen freshly-killed prey from the likes of sabre-toothed cats, depriving them of food.

“Our results suggest that substantial anthropogenic influence on biodiversity started millions of years earlier than currently assumed,” the researchers reported in the journal Ecology Letters.

Co-researcher Alexandre Antonelli of the Royal Botanic Gardens, Kew, said the view that our ancestors had little impact on the animals around them is incorrect, as “the impact of our lineage on nature has been far greater and longer-lasting than we ever could ever imagine”.

A landmark report last year warned that as many as one million species of animals and plants are threatened with extinction in the coming decades.

A more recent study found that the growth of cities, the clearing of forests for farming and the soaring demand for fish had significantly altered nearly three-quarters of the land and more than two-thirds of the oceans.

Building an Ark for the Anthropocene (New York Times)

CreditJason Holley

WE are barreling into the Anthropocene, the sixth mass extinction in the history of the planet. A recent study published in the journal Science concluded that the world’s species are disappearing as much as 1,000 times faster than the rate at which species naturally go extinct. It’s a one-two punch — on top of the ecosystems we’ve broken, extreme weather from a changing climate causes even more damage. By 2100, researchers say, one-third to one-half of all Earth’s species could be wiped out.

As a result, efforts to protect species are ramping up as governments, scientists and nonprofit organizations try to build a modern version of Noah’s Ark. The new ark certainly won’t come in the form of a large boat, or even always a place set aside. Instead it is a patchwork quilt of approaches, including assisted migration, seed banks and new preserves and travel corridors based on where species are likely to migrate as seas rise or food sources die out.

The questions are complex. What species do you save? The ones most at risk? Charismatic animals, such as lions or bears or elephants? The ones most likely to survive? The species that hold the most value for us?

One initiative, the Intergovernmental Platform on Biodiversity and Ecosystem Services formed in 2012 by the governments of 121 countries, aims to protect and restore species in wild areas and to protect species like bees that carry out valuable ecosystem service functions in the places people live. Some three-quarters of the world’s food production depends primarily on bees.

“We still know very little about what could or should be included in the ark and where,” said Walter Jetz, an ecologist at Yale involved with the project. Species are being wiped out even before we know what they are.

Another project, the EDGE of Existence, run by the Zoological Society of London, seeks to protect the most unusual wildlife at highest risk. These are species that evolved on their own for so long that they are very different from other species. Among the species the project has helped to preserve are the tiny bumblebee bat and the golden-rumped elephant shrew.

While the traditional approach to protecting species is to buy land, preservation of the right habitat can be a moving target, since it’s not known how species will respond to a changing climate.

To complete the maps of where life lives, scientists have enlisted the crowd. A crowdsourcing effort called the Global Biodiversity Information Facility identifies and curates biodiversity data — such as photos of species taken with a smartphone — to show their distribution and then makes the information available online. That is especially helpful to researchers in developing countries with limited budgets. Another project, Lifemapper, at the University of Kansas Biodiversity Institute, uses the data to understand where a species might move as its world changes.

“We know that species don’t persist long in fragmented areas and so we try and reconnect those fragments,” said Stuart L. Pimm, a professor of conservation at Duke University, and head of a nonprofit organization called SavingSpecies. One of his group’s projects in the Colombian Andes identified a forest that contains a carnivorous mammal that some have described as a cross between a house cat and a teddy bear, called anolinguito, new to science. Using crowd-sourced data, “we worked with local conservation groups and helped them buy land, reforest the land and reconnect pieces,” Dr. Pimm says.

Coastal areas, especially, are getting scrutiny. Biologists in Florida, which faces a daunting sea level rise, are working on a plan to set aside land farther inland as a reserve for everything from the MacGillivray’s seaside sparrow to the tiny Key deer.

To thwart something called “coastal squeeze,” a network of “migratory greenways” is envisioned so that species can move on their own away from rising seas to new habitat. “But some are basically trapped,” said Reed F. Noss, a professor of conservation biology at the University of Central Florida who is involved in the effort, and they will most likely need to be picked up and moved. The program has languished, but Amendment 1, on the ballot this November, would provide funding.

One species at risk is the Florida panther. Once highly endangered, with just 20 individuals left, this charismatic animal has come back — some. But a quarter or more of its habitat is predicted to be under some three feet of water by 2100. Males will move on their own, but females will need help because they won’t cross the Caloosahatchee River. Experts hope to create reserves north of the river, and think at some point they will have to move females to new quarters.

Protecting land between reserves is vital. The Yellowstone to Yukon Conservation Initiative, known as Y2Y, would protect corridors between wild landscapes in the Rockies from Yellowstone National Park to northern Canada, which would allow species to migrate.

RESEARCHERS have also focused on “refugia,” regions around the world that have remained stable during previous swings of the Earth’s climate — and that might be the best bet for the survival of life this time around.

A section of the Driftless Area encompassing northeastern Iowa and southern Minnesota, also known as Little Switzerland, has ice beneath some of its ridges. The underground refrigerator means the land never gets above 50 or so degrees and has kept the Pleistocene snail, long thought extinct, from disappearing there. Other species might find refuge there as things get hot.

A roughly 250-acre refugia on the Little Cahaba River in Alabama has been called a botanical lost world, because of its wide range of unusual plants, including eight species found nowhere else. Dr. Noss said these kinds of places should be sought out and protected.

Daniel Janzen, a conservation ecologist at the University of Pennsylvania who is working to protect large tracts in Costa Rica, said that to truly protect biodiversity, a place-based approach must be tailored to the country. A reserve needs to be large, to be resilient against a changing climate, and so needs the support of the people who live with the wild place and will want to protect it. “To survive climate change we need to minimize the other assaults, such as illegal logging and contaminating water,” he said. “Each time you add one of those you make it more sensitive to climate change.”

The Svalbard Global Seed Vault, beneath the permafrost on an island in the Arctic Ocean north of mainland Norway, preserves seeds from food crops. Frozen zoos keep the genetic material from extinct and endangered animals. The Archangel Ancient Tree Archive in Michigan, meanwhile, founded by a family of shade tree growers, has made exact genetic duplicates of some of the largest trees on the planet and planted them in “living libraries” elsewhere — should something befall the original.

In 2008, Connie Barlow, a biologist and conservationist, helped move an endangered conifer tree in Florida north by planting seedlings in cooler regions. Now she is working in the West. “I just assisted in the migration of the alligator juniper in New Mexico by planting seeds in Colorado,” she said. “We have to. Climate change is happening so fast and trees are the least capable of moving.”