Rising temperatures and species extinction linked, researchers say
25 Ottobre 2007
Global temperatures predicted for the coming centuries could wipe out over 50% of existing animal and plant species, scientists from the Universities of York and Leeds warn. Studying nearly the
entire fossil record available, they discovered that there has been a close link between Earth’s climate and the extinction of species over the past 520 million years.
Biodiversity in marine and terrestrial fossils shows that the number of species decreases considerably during warm ‘greenhouse’ phases. During cooler ‘icehouse’ phases, on the other hand, the
reverse is true.
‘Our results provide the first clear evidence that global climate may explain substantial variation in the fossil record in a simple and consistent manner,’ says Dr Peter Mayhew, population
ecologist at the University of York. ‘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.’
Over the period now comprehensively studied by the researchers for the first time, there were five major mass extinction events. Four of those were associated with greenhouse phases.
About 65 million years ago, 16% of marine families, 47% of marine genera (groups of species exhibiting similar characteristics) and 18% of land vertebrate families – including dinosaurs –
disappeared. In this case, the effect of the heat was probably aggravated by the impact of a large asteroid on the Yucatan Peninsula. Fossils indicate similar or even higher death tolls during
the End-Triassic (200 to 214 million years ago), the End-Permian (about 251 million years ago), the Late Devonian (about 364 million years ago) and the Ordovician-Silurian (439 million years
‘The long-term association has not been seen before, as previous studies have largely been confined to relatively short geological periods, limited geographical extents and few groups of
organisms,’ Professor Tim Benton from the University of Leeds explains. ‘But the evidence is striking.’