Changing vegetation killed off the woolly mammoth

Changing vegetation killed off the woolly mammoth

Woolly mammoths and other herbivores lived primarily on grasses, especially protein rich forbs.

Scientists have known for some time that climate change somehow resulted in the extinction of the woolly mammoth, woolly rhino and other ice age mammals. Until now it was unclear exactly what happened to cause the extinction as temperatures warmed and vegetation became more abundant. Eske Willerslev and other researchers at the University of Copenhagen think they have the answer.

Contrary to popular belief, the northern hemisphere had an abundance of plant life during the last ice age. Woolly mammoths and other herbivores of the era lived primarily on grasses, especially protein rich forbs. Forbs are herbaceous flowering plants. Modern examples include milkweed, saltworts, dandelion, cumin, ribwort and sunflowers, which are especially large for a forb.

As the Ice Age reached its coldest and driest points, 15,000 – 25,000 years ago, plants became more scarce and the mammoth population declined but did not die out. When the Ice Age ended, about 10,000 years ago, plant life became more abundant again but the forbs that the large mammals depended on did not. Instead they were replaced by other types of vegetation.

It is the loss of this protein rich food source that likely doomed the woolly mammoth, wooly rhino and other ice age mammals.

“We knew from our previous work that climate was driving fluctuations of the megafauna populations, but not how. Now we know that the loss of protein-rich forbs was likely a key player in the loss of the ice age megafauna. Interestingly one can also see our results in the perspective of the present climate changes. Maybe we get a hold on the greenhouse gases in the future. But don’t expect the good old well-known vegetation to come back when it becomes cooler again after the global warming. It is not given that the ‘old’ ecosystems will re-establish themselves to the same extent as before the warming. It’s not only climate that drives vegetation changes, but also the history of the vegetation itself and the mammals consuming it,” says Eske Willerslev.

The researchers studied 242 permafrost sediment samples and eight fossil samples from large mammals from around the Arctic. The samples were dated and analyzed for DNA. The gut content from permafrozen woolly rhinos, mammoth and other extinct ice age mammals was also studied.

The findings were published in the journal Nature.

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