Archives par mot-clé : Extinction

Human ancestors not to blame for ancient mammal extinctions in Africa

by University of Utah, November23, 2018 in ScienceDaily


New research disputes a long-held view that our earliest tool-bearing ancestors contributed to the demise of large mammals in Africa over the last several million years. Instead, the researchers argue that long-term environmental change drove the extinctions, mainly in the form of grassland expansion likely caused by falling atmospheric carbon dioxide (CO2) levels.

The study is published today in the journal Science.

“Despite decades of literature asserting that early hominins impacted ancient African faunas, there have been few attempts to actually test this scenario or to explore alternatives,” Faith says. “We think our study is a major step towards understanding the depth of anthropogenic impacts on large mammal communities, and provides a convincing counter-argument to these long-held views about our early ancestors.”

To test for ancient hominin impacts, the researchers compiled a seven-million-year record of herbivore extinctions in eastern Africa, focusing on the very largest species, the so-called ‘megaherbivores’ (species over 2,000 lbs.) Though only five megaherbivores exist in Africa today, there was a much greater diversity in the past. For example, three-million-year-old ‘Lucy’ (Australopithecus afarensis) shared her woodland landscape with three giraffes, two rhinos, a hippo, and four elephant-like species at Hadar, Ethiopia.

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Geologists uncover new clues about largest mass extinction ever

by University of Tennessee at Knoxville, August 27, 2018 in ScienceDaily from Nature.


Through the analysis of samples, Broadley and his team tried to determine the composition of the lithosphere. They found that before the Siberian Flood Basalts took place, the Siberian lithosphere was heavily loaded with chlorine, bromine, and iodine, all chemical elements from the halogen group. However, these elements seem to have disappeared after the volcanic eruption.

“We concluded that the large reservoir of halogens that was stored in the Siberian lithosphere was sent into the earth’s atmosphere during the volcanic explosion, effectively destroying the ozone layer at the time and contributing to the mass extinction,” Broadley said.

The sixth mass genesis? New species are coming into existence faster than ever thanks to humans

by Prof. Chris D. Thomas, July 10, 2017 in TheConversation


Animals and plants are seemingly disappearing faster than at any time since the dinosaurs died out, 66m years ago. The death knell tolls for life on Earth. Rhinos will soon be gone unless we defend them, Mexico’s final few Vaquita porpoises are drowning in fishing nets, and in America, Franklin trees survive only in parks and gardens.

Yet the survivors are taking advantage of new opportunities created by humans. Many are spreading into new parts of the world, adapting to new conditions, and even evolving into new species … (…)

What caused the mass extinction of Earth’s first animals?

by Arizona State University, June 27, 2018 in ScienceDaily


Scientists have argued for decades over what may have caused this mass extinction, during what is called the “Ediacaran-Cambrian transition.” Some think that a steep decline in dissolved oxygen in the ocean was responsible. Others hypothesize that these early animals were progressively replaced by newly evolved animals.

The precise cause has remained elusive, in part because so little is known about the chemistry of Earth’s oceans that long ago.

A research team, led by scientists from Arizona State University and funded by NASA and the National Science Foundation, is helping to unravel this mystery and understand why this extinction event happened, what it can tell us about our origins, and how the world as we know it came to be. The study, published in Science Advances, was led by ASU School of Earth and Space Exploration graduate student Feifei Zhang, under the direction of faculty member Ariel Anbar and staff scientist Stephen Romaniello. (…)

When the dinosaurs died, so did forests — and tree-dwelling birds

By Field Museum, May 24, 2018 in ScienceDaily (CurrentBiology)


Sixty-six million years ago, the world burned. An asteroid crashed to Earth with a force one million times larger than the largest atomic bomb, causing the extinction of the dinosaurs. But dinosaurs weren’t the only ones that got hit hard — in a new study, scientists learned that the planet’s forests were decimated, leading to the extinction of tree-dwelling birds.

Invisible Scientific Debates Accomplish Nothing

by Donna Laframboise, April 23, 2018 in ClimateChangeDispatch


SPOTLIGHT: After the Intergovernmental Panel on Climate Change (IPCC) report was released in 2007, its dramatic findings of species extinction were repeatedly emphasized by chairman Rajendra Pachauri.

BIG PICTURE: When it examined the question of species extinction, the 2007 IPCC report relied heavily on a single piece of research – a Nature cover storypublished early in 2004. Written by Chris Thomas and 18 others, this was the source of Pachauri’s claim that climate change threatened 20 to 30% of the world’s species.

Studying oxygen, scientists discover clues to recovery from mass extinction

by Arizona State University, April  17, 2018 in ScienceDaily


About 252 million years ago, more than 90 percent of all animal life on Earth went extinct. This event, called the “Permian-Triassic mass extinction,” represents the greatest catastrophe in the history of life on Earth. Ecosystems took nearly five million years to recover and many aspects of the event remain a mystery.

A research team, led by scientists from Arizona State University and funded by NASA and the National Science Foundation, is helping to understand why this extinction event happened and why it took life so long to recover. The study, published in Science Advances, was led by ASU School of Earth and Space Exploration graduate student Feifei Zhang, with direction from school faculty member Ariel Anbar.

Extinction and global warming 250 million years ago

by U. of Bristol, January 10, 2018 in A Watts, WUWT


One of the key effects of the end-Permian mass extinction, 252 million years ago, was rapid heating of tropical waters and atmospheres.

How this affected life on land has been uncertain until now.

In a new study published today, Dr Massimo Bernardi and Professor Mike Benton from the School of Earth Sciences at the University of Bristol show how early reptiles were expelled from the tropics.

Volcanic eruptions drove ancient global warming event

by Marcus Gutjah et al., August 30,  2017 in PhysOrg


A natural global warming event that took place 56 million years ago was triggered almost entirely by volcanic eruptions that occurred as Greenland separated from Europe during the opening of the North Atlantic Ocean,

The amount of carbon released during this time was vast—more than 30 times larger than all the fossil fuels burned to date and equivalent to all the current conventional and unconventional fossil fuel reserves we could feasibly ever extract.” Ridgwell said.

An unexpected finding was that enhanced organic matter burial was important in ultimately sequestering the released carbon and accelerating the recovery of the Earth’s ecosystem without massive extinctions.

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Dino-killing asteroid could have thrust Earth into two years of darkness

by National Center for Atmospheric Research/University Corporation for Atmospheric Research, August 21, 2017 in ScienceDaily


Tremendous amounts of soot, lofted into the air from global wildfires following a massive asteroid strike 66 million years ago, would have plunged Earth into darkness for nearly two years, new research finds. This would have shut down photosynthesis, drastically cooled the planet, and contributed to the mass extinction that marked the end of the age of dinosaurs.

Underground magma triggered Earth’s worst mass extinction with greenhouse gases

by Howard Lee, geologist, August 9, 2017 in WUWT


Earth’s most severe mass extinction, the “Great Dying,” began 251.94 million years ago at the end of the Permian period, with the loss of more than 90% of marine species. Precise rock dates published in 2014 and 2015 proved that the extinction coincided with the Siberian Traps LIP, an epic outpouring of lava and intrusions of underground magma covering an area of northern Asia the size of Europe.

But those rock dates presented science with a new puzzle: why was the mass extinction event much shorter than the eruptions? And why did the extinction happen some 300,000 years after the lava began to flow?

Flourishing ocean drives the end-Permian marine mass extinction

by Martin Schobben et al., July 2014,


The Permian geologic period that ended the Paleozoic era climaxed around 252 million years ago with a sweeping global mass extinction event in which 90 to 95 percent of marine life became extinct. It would take 30 million years for planetary biodiversity to recover. Understanding the contributing factors of the end-Permian mass extinction is critical to understanding and perhaps mitigating the current anthropogenic climate change.

Earth Is Not in the Midst of a Sixth Mass Extinction

by Peter Brannen, June 14, 2017


“It is absolutely critical to recognize that I am NOT claiming that humans haven’t done great damage to marine and terrestrial [ecosystems], nor that many extinctions have not occurred and more will certainly occur in the near future. But I do think that as scientists we have a responsibility to be accurate about such comparisons.”

Many popular science articles take this as a given, and indeed, there’s something emotionally satisfying about the idea that humans’ hubris and shortsightedness are so profound that we’re bringing down the whole planet with us.