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Does Global Warming Cause Mass Extinctions?

11.12.2013
11.12.2013 16:20 Age: 253 days

Geological evidence suggests that mass extinctions in the past were associated with global warming events.

Click to enlarge. St Audrie's Bay, United Kingdom. Rock samples were collected from this location to determine the oceanic and atmospheric conditions that caused the end-Triassic extinction 200 million years ago. Courtesy: L. Felipe Opazo, Plymouth University.

 

by Megan Meates , Curtin University

Researchers have discovered two of Earth’s ancient mass extinctions wiped out life on the planet in a similar way to one another and that both were associated with global warming conditions.


Research led by Curtin University in Perth, Western Australia, and published in Geology, demonstrated the cascade of events during the fourth largest extinction, at the end of the Triassic period 200 million years ago, were remarkably similar to those of the largest extinction that occurred at the end of the Permian 250 million years ago.


The research suggests perhaps all global warming-related mass extinctions show similar patterns of change.


From rock samples collected by colleagues in Plymouth University, lead scientists Professor Kliti Grice, Director of the WA Organic and Isotope Geochemistry Centre (WA-OIGC) program and Dr Caroline Jaraula and Dr Pierre Le Metayer, Research Fellows of the WA-OIGC program from Curtin, discovered and examined molecular fossils of land plants, algae and green sulfur bacteria (known as Chlorobi).


Alongside their international research team, they were able to determine the oceanic and atmospheric conditions that caused the end-Triassic extinction 200 million years ago.


“Back then, the world’s continents were being pulled apart to create what is now the Atlantic Ocean. This event was accompanied by frequent, massive volcanic eruptions that injected great quantities of CO2 into atmosphere, estimated at four times higher than today’s levels based on plant physiology,” Professor Grice said.


“The high CO2 levels triggered global warming; leading to a cascade of atmospheric and oceanic changes that were very similar to those that we found had caused the largest mass extinction, which happened 50 million years prior to this one.

 

Extinctions associated with global warming

“Of the five mass extinctions to have ever occurred in the past 600 million years, four were associated with global warming. Our research suggests if two of these had similar processes operating, perhaps all other global warming-related extinctions do too, helping us understand more about Earth’s history.”


Dr Jaraula said the research team looked at stable carbon isotopes of molecular fossils of plant waxes, algae and chlorobi before, during and after the extinction period.


Professor Richard Twitchett of Plymouth University said the next step was to compare the results to changes in the fossil record of marine animals, to help understand how future marine extinctions are likely to occur.

 

Glimpse

“Our study has provided a glimpse of how extinctions happen and their rates of change. While ocean circulation and aspects of the carbon cycle will always be different, the general patterns of change can still be compared,” Professor Michael Böttcher, of the Leibniz Institute for Baltic Sea Research, Germany, said.


Professor Grice and her research colleagues previously determined the conditions of the largest extinction occurring at the end of the Permian, 250 million years ago in a report published in Science in 2005.


The recently published research in Geology was carried out in conjunction with Plymouth University and Leibniz Institute for Baltic Sea Research, Germany.


The research has been funded by the Australian Research Council under a QEII Discovery Fellowship awarded to Professor Grice and Professor Twitchett. Professor Grice has also recently been awarded a Discovery Outstanding Research Award to continue this research and investigate the recovery of the largest extinction events and their association with oil and gas resources on a global scale.


The paper entitled “Elevated pCO2 leading to Late Triassic extinction, persistent photic zone euxinia, and rising sea levels” was published in Geology.


Abstract

The Late Triassic mass extinction event is the most severe global warming-related crisis to have affected important extant marine groups such as scleractinian corals, and offers potential insights into climate change scenarios. Here we present evidence from Chlorobi-derived biomarkers of episodic and persistent photic zone euxinia. From biomarkers and stable carbon isotopes, we present evidence of rapid mixing of atmospheric and oceanic carbon reservoirs. Global versus regional trends are resolved in kerogen organic matter type, carbonate δ13C, and bulk and pyrite δ34S. This suite of data demonstrates for the first time a comprehensive organic and stable isotope geochemical reconstruction of events leading up to the Late Triassic extinction event and its aftermath. The cascade of events prior to, during, and after the extinction is remarkably similar to those reported for the Late Permian extinction, the largest extinction event of the Phanerozoic. We predict that similar conditions will have occurred during all past episodes of rapid global warming and biotic crisis that are associated with similar rises in pCO2.


Citation

“Elevated pCO2 leading to Late Triassic extinction, persistent photic zone euxinia, and rising sea levels” by Caroline M.B. Jaraula, Kliti Grice1, Richard J. Twitchett, Michael E. Böttcher, Pierre LeMetayer, Apratim G. Dastidar and L. Felipe Opazo published in Geology.

doi: 10.1130/G34183.1

Read the abstract and get the paper here

 

Source

This story based on a news release from Curtin University here


 


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