A major decline in plant diversity resulted in the extinction of the woolly mammoth, woolly rhinoceros and many other large animals following the last Ice Age, according to a new study published in the journal Nature.
Relying on DNA-based research, the Centre for GeoGenetics at the Natural History Museum of Denmark has found that the flowering plants that mammoths and other large creatures depended on for survival disappeared from North American and northern Asia during the last glacial period, eliminating a major food source for the animals.
Prior the that period, the landscapes of the Northern hemisphere were far more diverse and stable than today’s steppes, with megafauna like woolly rhinos and mammoths feeding on grasses and protein-rich flowering plants, or forbs.
But at the height of the last Ice Age – 25,000-15,000 years ago, at a time when the climate was at its coldest and driest – a major loss of plant diversity occurred, the study’s authors wrote.
As a result, the giant animals barely survived.
Once the Ice Age ended about 10,000 years ago the climate warmed again. However, the protein-rich forbs did not recover to their former abundance and were replaced with different kinds of vegetation, including grasses prevalent on today’s plains and steppes.
“This likely proved fatal for species like woolly rhino, mammoth, and horse in Asia and North America,” according to the University of Copenhagen. “Even though it became warmer again after the end of the Ice Age the old landscapes did not return.”
“We knew from our previous work that climate was driving fluctuations of the megafauna populations, but not how,” said study author Eske Willerslev of the Centre for GeoGenetics. “Now we know that the loss of protein-rich forbs was likely a key player in the loss of the Ice Age megafauna.”
The research team sampled permafrost cores dating back 50,000 years from 17 spots in northern Russian, Canada and Alaska. They found DNA signatures inside the cores showing that flowering species, and the tiny roundworms connected with them living in the soil, were more prevalent than grasses on the ancient steppes, according to RedOrbit.
The team also analyzed 18 archival samples of stomach contents and feces from mammoths, woolly rhinos, horses, reindeer and elk, discovering that flowering species were a significant portion of the animals’ diet, the online publication added.
“We show that the permafrost contains a vast, frozen DNA archive left as footprints from past ecosystems, and that we can (decipher) this archive by exploring the collections of plants and animals stored in Natural History Museums,” said study author Christian Brochmann, a botanist at the Natural History Museum at the University of Oslo in Norway.
“Using DNA from museum collections as reference, we could identify the different plant species that co-occurred with extinct Ice Age mammals,” he added.
Other theories on why megafauna went extinct include the devastating effects of a comet impact and overhunting by humans.