Climate change has been a significant factor in mass mammal extinction over most of the last fifty thousand years, according to an international team.
The team used global data modelling to build continental ‘climate footprints’ and map them on to extinction data.
“Between 50,000 and 3,000 years before present (BP), 65 percent of mammal species weighing over 44kg went extinct, together with a lower proportion of small mammals,” says lead author Dr David Nogues-Bravo from the University of Copenhagen.
“Why these species became extinct in such large numbers has been hotly debated for over a century.”
Over most of the last 50,000 years, the global climate became colder and drier, reaching full glacial conditions 21,000 years ago.
Since then, it’s has become warmer, leading to colonization of new regions by humans – and many believed that it was this human colonization that cause the mass extinctions.
The study shows that climate change had a global influence over extinctions throughout the late quaternary, but the level of extinction seems to be related to each continent’s footprint of climate change.
In Africa, for example, where the climate changed relatively little, there were fewer extinctions. However, in North America, which experienced more climate change, more species suffered extinction.
A key piece of evidence in the humans versus climate debate is the size of the extinct mammals. It has always been assumed that humans mainly impacted on large mammals, while if climate change played the key role there should be evidence of major impacts on small mammals as well.
The team’s results show that continents which suffered most climate change suffered larger extinctions of small mammals and vice versa.
“While climate change is not the only factor behind extinction, past, present or future, we cannot neglect in any way that climate change, directly or indirectly, is a crucial actor to understand past and future species extinctions,” said Miguel Araújo, a co-author of the paper from the National Museum of Natural Sciences in Spain.
Their paper appears in Evolution.