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lunedì 5 dicembre 2016

THE EXTINCTION VORTEX

The sixth mass extinction — the one that seven billion humans are sadly doing their utmost to trigger at this very moment — is shaping up to be like nothing our planet has ever seen. That’s the conclusion of a sweeping new analysis, which compared marine fossil records from Earth’s five previous mass extinction events to what’s happening in the oceans right now.



There is no past event that looks biologically like what’s happening today,” lead study author Jonathan Payne, of Stanford University, told Gizmodo. Unlike the past, Payne said, “processes like warming and ocean acidification are not the dominant cause of threat in the modern ocean”.



Instead, the dominant threat is people. It’s the nets, harpoons, and trawlers that are systematically emptying the oceans of fish and other marine life forms. Whereas the mass extinctions of the past tended to target organisms in certain environments, the sixth mass extinction is poised to hit the biggest animals the hardest. And that could have have profound implications for how our planet’s future unfolds.



A palaeontologist by training, Payne and his research group started compiling data on modern marine organisms several years back, in order to study how body size and ecological traits have changed over evolutionary time. Payne, who has studied the End Permian extinction event, which wiped out more than 95 per cent of all marine species 250 million years ago, soon realised that his dataset — comprising living and extinct members of nearly 2500 marine genera — could serve another purpose.


“We thought the data we had would allow us to examine extinction in the modern [era] in a way that would be very comparable to the fossil record,” Payne said. “Our hope was that we might be able to identify past events that biologically were most similar to the extinction threat the oceans are facing today.”


So that’s exactly what the researchers did. By comparing the extinction threat faced by modern marine genera (as indicated by their official conservation status) with their ancestral counterparts, Payne and his colleagues discovered that modern extinction threat is more strongly associated with body size. Larger animals face a greater risk of disappearing than smaller animals.


In past mass extinction events, body size didn’t matter that much. Instead, it was an organism’s habitat that dictated its fate. Animals that lived in the open ocean, or pelagic zone, went extinct at a higher rate than benthic creatures living on the seafloor.



This difference in “extinction selectivity” can be explained by different drivers. During the End Permian, changes in ocean chemistry triggered by microbes, volcanoes, or some combination of the two are thought to have created a toxic environment for most marine life. At the end of the Cretaceous period, an enormous asteroid impact followed by supervolcano eruptions sent plumes of dust into the sky, choking out sunlight and cutting off the energy supply at the bottom of the food chain. In both cases, organisms that lived in more isolated, sheltered environments away from the ocean’s surface fared better.


Today, the dominant driver of marine extinction is people, and people aren’t terribly selective about what environments they pluck animals from. We go for the biggest game, fishing down the food web and removing top predators. Within species, too, we tend to hunt the largest individuals, which is why North Atlantic cod and Chesapeake oysters were historically much larger. “In a sense, we’re driving evolution [toward smaller individuals],” Payne said.


There are a few big caveats to the analysis. For the sake of comparison, Payne and his co-authors only analysed marine genera that have fossil counterparts, which means certain soft-bodied organisms that don’t preserve well (like octopods) were excluded. What’s more, they only looked at organisms whose extinction risk has been assessed by the International Union for the Conservation of Nature (IUCN). That creates a rather serious bias toward big, charismatic groups: fish, sea turtles, marine mammals, and the like. There are countless species of marine invertebrates that we simply don’t have enough data on to do a proper threat assessment.


Perhaps most problematically, the study excluded corals, which are currently in the midst of a catastrophic, global die-off. As habitat for roughly a quarter of all marine species, the loss of coral reefs due to global warming and ocean acidification would undoubtedly be a major blow to the health of the oceans overall.


Even considering these omissions, the pattern the authors uncovered implies that the trajectory of the sixth mass extinction could be unique. The loss of large animals tends to cause what ecologists call a “tropic cascade”, which is essentially a ripple effect down the food chain. Larger organisms also play an outsized role in global nutrient cycling: whale faeces fertilises the oceans with iron, for instance, while salmon migrations bring nitrogen and phosphorus upstream and even onto the land.


It’s unclear whether the loss of these ecosystem services will make it harder for marine life to recover, but it’s certainly a possibility. The study minces no words to this point: “the preferential removal of the largest animals from the modern oceans, unprecedented in the history of animal life, may disrupt ecosystems for millions of years.”


There is, however, a bright spot: things haven’t got too terrible yet. In Payne’s dataset, there is only one genus that has actually gone extinct in the past 500 years. While more species have gone extinct, and some genera are too poorly studied to be sure, we’re at best on the precipice of a sixth mass extinction. We can still turn this sinking ship around.

“We have the opportunity to totally avert this, if we make the right decisions,” Payne said. “Even on the land, where we have lost a bunch of large species, almost everything at the genus level is still here.”

“To claim we’re in a sixth mass extinction is something very enormous,” he continued. “It is a possibility. It is not the reality yet.”

THE SIXTH MASS EXTINCTION WILL BE LIKE NOTHING IN EARTH’S HISTORY corespirit

Climate Change Will Accelerate Earth's Sixth Mass Extinction Sarah Zielinski SMITHSONIAN.COM  

A new report indicates that more than half of wild primate species are facing extinction.

The study, which was conducted by a team of 31 leading scientists from across the globe, looked at the current data we have on the state of primates around the world and the challenges they face, utilizing data from the International Union for the Conservation of Nature (IUCN) among other sources. While we have several smaller studies that give us a worrying insight into the decline of primates, this research aims to provide a broader snapshot—and the results aren't encouraging.


There’s new evidence that some of the large creatures that once roamed Australia – what scienitsts call Australia’s ancient megafauna – didn’t disappear due to climate change as had been proposed earlier. Instead, the evidence suggests that humans were the primary cause of these unique creatures’ sudden extinction some 45,000 years ago. Prior to that time, were 1,000-pound kangaroos in Australia, 2-ton wombats, 25-foot-long lizards, 400-pound flightless birds, 300-pound marsupial lions and Volkswagen-sized tortoises. After that time, those huge creatures had disappeared.
A science team led by Sander van der Kaars of Monash University in Australia used information from a sediment core drilled in the Indian Ocean off the coast of southwest Australia to help reconstruct past climate and ecosystems on the Australian continent. The core contains layers of material blown and washed into the ocean over time, and so looking deeper in the sediments is the same as looking deeper into the past. The team’s paper on this subject was published online January 20, 2017 in the peer-reviewed journal Nature Communications.
Gifford Miller at the University of Colorado Boulder (CU Boulder) was a member of the research team. He said in a statement from CU Boulder that the sediment core let scientists look back more than 150,000 years, a time period spanning Earth’s last full glacial cycle.
He said the sediments his team exacontained dust, pollen, ash and spores from a fungus called Sporormiella, which can still be found today in the dung of domestic livestock. In the past, as now, this spore thrived on the dung of plant-eating mammals. Miller said his team found the spores in abundance in the sediment layers from 150,000 years ago to about 45,000 years ago. Then, suddenly, the number of spores in the sediments went into a nosedive. He added:
The abundance of these spores is good evidence for a lot of large mammals on the southwestern Australian landscape up until about 45,000 years ago. Then, in a window of time lasting just a few thousand years, the megafauna population collapsed.
The first humans arrived in Australia about 50,000 years ago. Miller said that more than 85 percent of Australia’s mammals – birds and reptiles weighing over 100 pounds – went extinct a few thousand years after the first humans arrived.
This isn’t Miller’s first foray into the world of early humans in Australia, and the results of their hunting. In 2016, he used burned eggshells of the 400-pound bird, Genyornis, as the first direct evidence that humans actually preyed on the Australian megafauna.
According to the CU Boulder statement, scientists have been debating the causes of the Australian megafauna extinctions for decades:
Some claim the animals could not have survived changes in climate, including a shift some 70,000 years ago when much of the southwestern Australia landscape went from a wooded eucalyptus tree environment to an arid, sparsely vegetated landscape.
Others have suggested the animals were hunted to extinction by Australia’s earliest immigrants who had colonized most of the continent by 50,000 years ago, or a combination of overhunting and climate change.
But Miller believes now that humans were the primary cause of the extinction, which might have been caused by what he called imperceptible overkill. He bases that idea on a 2006 study by Australian researchers, which indicated that even low-intensity hunting of Australian megafauna – like the killing of one juvenile mammal per person per decade – could have resulted in the extinction of a species in just a few hundred years. Sander van der Kaars, the study leader, said:
The results of this study are of significant interest across the archaeological and Earth science communities and to the general public who remain fascinated by the menagerie of now extinct giant animals that roamed the planet – and the cause of their extinction – as our own species began its persistent colonization of Earth.
They’re also food for thought for anyone who believes that the activities of a few or a lot of humans can’t have a large effect on the environment.

Early humans wiped out big animals in Australia Deborah Byrd January 25, 2017


Humanity driving 'unprecedented' marine extinction 15 SETTEMBRE 2016



The World's Largest Animals Are Close To Disappearing 25 AGOSTO 2016 


Bird Snatching Bandits Kidnap African Grey Parrot to Near Extinction in Ghana Emerson Urry February 17, 2016 

Save the Pacific Bluefin Tuna  and 


Over 50% of sharks and rays in the Mediterranean Sea are at risk of extinction 6 December 2016 / Shreya Dasgupta 

Carnage for dolphins on Killer Whales: The Mega Hunt 4th December 2016 James Wray 

Can Anything Save the Sumatran Rhino From Extinction? Jani ActmanNational Geographic  

A Rare Look at the Disappearing World of Antarctica's Whales Douglas Fox DECEMBER 6, 2016 

Another Arctic Species Losing Out as Sea Ice Declines: The Ivory Gull John R. Platt on November 30, 2016

A third of the world's Polar Bears facing extinction 7 Dec 2016 Michael Staines

The Last Leopards 2 7 DICEMBRE 2016 


SNOWBALL EFFECT

The term “snowball effect” is an unfortunate way to describe climate change, but a new study is predicting just that.
Climate scientists warn that by 2050, an astonishing 55 trillion kilograms of carbon could be released into the atmosphere from the soil. To put things in perspective, that’s the emissions equivalent of adding another United States to the planet. And, like a rapidly tumbling snowball, more emissions mean more warming, and more warming means… well, you get it.
Of course, this nightmare scenario hinges on our inability to curb carbon emissions—a fate that’s become significantly more realistic with Donald Trump, a vocal climate change denier and coal aficionado, about to enter the White House. Our failure to meet the goals mandated by the Paris Agreement would result in “about 17 percent more than the projected emissions due to human-related activities during that period,Tom Crowther, the study’s lead author and a researcher at the Netherlands Institute of Ecology, said in a statement.
The new study, which was published in Nature this week, presents findings from a global survey of soil data collected over the past 20 years. Scientists have been researching terrestrial carbon for decades, not only over its potential to emit greenhouse gases, but also for its ability to store them. However, Crowther claims this is the first time a worldwide perspective of soil emissions has ever been presented.
Unlike other surveys, Crowther said, this one considered carbon losses from some of the coldest places on Earth.
In the Arctic, for example, enormous caches of carbon have accumulated in the soil over thousands of years. Because of freezing temperatures, the microbes that normally stimulate the release of carbon through decomposition are less active in these regions. But as temperatures continue to rise, as they’ve done precipitously this year, these microbes could become more lively, accelerating the rate at which carbon is emitted into the atmosphere.
“Carbon stores are greatest in places like the Arctic and the sub-Arctic, where the soil is cold and often frozen,” Crowther added. “The scary thing is, these cold regions are the places that are expected to warm the most under climate change.”
The 55 trillion kilograms of emissions would come in the form of carbon dioxide (CO2) and methane, according to the study. Methane, which possesses up to 25 times the warming power of CO2, is especially concerning in parts of Siberia where melting permafrost is causing strange natural phenomena to literally bubble up from underground. In an interview with Alex Verbeek, Crowther said these effects could be worsened by carbon emissions from soil deposits.
To slow down or offset these processes, things like carbon sequestration and plant growth could help. But as the study notes, the net effect of such strategies require further investigation.
“Getting a handle on these kinds of feedbacks is essential if we’re going to make meaningful projections about future climate conditions,” Crowther added.
“Only then can we generate realistic greenhouse gas emission targets that are effective at limiting climate change.”


NASA photo reveals massive rift in Antarctic ice that will produce iceberg the size of Delaware December 4, 2016


Marina Abramović and Mark Ruffalo Speak Out in New Climate Change Documentary Diana Shi — Dec 3 2016



Technosphere and Sixth Mass Extinction 20 OTTOBRE 2015


The Annihilation of Nature 12 NOVEMBRE 2015


Carbon emissions put sixteen percent of species at risk of extinction May 14, 2015



Capitalist Greed Pushing The World Into The Sixth Extinction 25 AGOSTO 2015



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