Climate change, rather than human hunters, drove the wooly mammoth to extinction. That’s the claim from scientists who say that the hairy beasts lost their grazing grounds as forests rapidly replaced grasslands after the last ice age, roughly 20,000 years ago. The researchers used palaeoclimate and vegetation models to simulate the plant cover across the mammoths’ habitat around that time. And the results are striking. “The landscape at the last glacial maximum would have been dominated by grasses and small shrubs and bushes, a perfect vegetation for mammoths and other megafaunal grazers,” explains Judy Allen, a palaeoecologist at Durham University, UK and lead author of the study. "But as the climate warmed, the mammoths habitat of grassland was completely taken over by forest," she says. The tree takeover was boosted by more intense sunlight and higher levels of carbon dioxide in the atmosphere. (see BBC and Daily Telegraph).
Not only did this change happen across a vast area covering modern day Europe and North America, it also happened very fast. “We’re talking about a warming over a 2,000 to 5,000 year period,” says Brian Huntley, a Durham palaeoecologist and co-author of the study. “In just a few thousand years the mammoth’s habitat and food source more or less disappeared”. The research is published in Quaternary Science Reviews.
But why didn’t the mammoths just adapt? “It took a couple of millions of years for the mammoth lineage to evolve through to the woolly mammoths adapted to the cold and grassland conditions,” says Huntley. “A few thousand years would be insufficient time for a large animal like the mammoth with slow regeneration time to adapt quick enough.”
In fact, the woolly mammoth’s mouthparts were specially adapted for feeding on grass, with studies showing that it had evolved into two groups by around 40,000 years ago (see ‘Woolly mammoth family tree grows a new branch’).
Yet humans aren’t quite off the hook. “Our results show that a warming climate about 20,000 years ago would have put a lot of environmental stress on mammoths and other megafauna,” says Allen. “But there is no doubt that humans hunted mammoths. And as the climate warmed, human hunting may have led to the final demise of an already environmentally stressed species.”