Worst mass extinctions occur when temperatures are the warmest
Rhett A. Butler, mongabay.com
October 24, 2007




Warming temperatures could trigger a ‘mass extinction event', warn scientists writing in the latest issue of Proceedings of the Royal Society B.

Comparing ancient records of marine and terrestrial diversity with historical temperature estimates, researchers from the Universities of York and Leeds found a close correlation between Earth climate and extinctions over the past 520 million years: higher extinction rates occur at higher temperatures.

"We found that over the fossil record as a whole, the higher the temperatures have been, the higher the extinctions have been," lead author Peter Mayhew, a University of York ecologist, told the Associated Press.




    Countries with the highest number of threatened (top) and extinct (bottom) species according to 2006 IUCN Red List data. The "threatened" chart includes species listed as Critically Endangered (CR), Endangered (EN) or Vulnerable (VU) by IUCN, while the "extinct" chart includes species classified as "Extinct (EX)" or "Extinct in the Wild (EW)" on the Red List. Both charts include mammals, birds, reptiles, amphibians, fishes, mollusks, other invertebrates, and plants to the totals.

Mayhew, together with University of York student Gareth Jenkins and University of Leeds Professor Tim Benton, say that temperatures forecast over the next century are "within the range of the warmest greenhouse phases that are associated with mass extinction events identified in the fossil record."

"Our results provide the first clear evidence that global climate may explain substantial variation in the fossil record in a simple and consistent manner. If our results hold for current warming - the magnitude of which is comparable with the long-term fluctuations in Earth climate - they suggest that extinctions will increase," said Mayhew.

The researchers note that four of the five historical mass extinction events are associated with warm greenhouse phases. The largest mass extinction event of all, the end-Permian when 95 percent of animal and plant species disappeared, occurred during one of the warmest-ever climate phases.

Ecologists have long warned that the human-induced climate warming could trigger a massive die-off of species. Dr. Thomas Lovejoy, a leading biologist who coined the term "biological diversity", estimate that 10-20 percent of all species could go the way of dinosaurs by the year 2020. Peter Raven, another leading scientists, has predicted that 565 species of mammals and at least 500 species of birds will go extinct within the next 50 years.

CITATION: Peter J. Mayhew, Gareth B. Jenkins, Timothy G. Benton (2007). A long-term association between global temperature and biodiversity, origination and extinction in the fossil record. Proceedings of the Royal Society B Tuesday, October 23, 2007

ABSTRACT: The past relationship between global temperature and levels of biological diversity is of increasing concern due to anthropogenic climate warming. However, no consistent link between these variables has yet been demonstrated. We analysed the fossil record for the last 520Myr against estimates of low latitude sea surface temperature for the same period. We found that global biodiversity (the richness of families and genera) is related to temperature and has been relatively low during warm ‘greenhouse' phases, while during the same phases extinction and origination rates of taxonomic lineages have been relatively high. These findings are consistent for terrestrial and marine environments and are robust to a number of alternative assumptions and potential biases. Our results provide the first clear evidence that global climate may explain substantial variation in the fossil record in a simple and consistent manner. Our findings may have implications for extinction and biodiversity change under future climate warming. (The Royal Society)


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CITATION:
Rhett A. Butler, mongabay.com (October 24, 2007).

Mass extinctions happen when temperatures are the warmest.

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