As appearing in CSU SOURCE | 10.9.19

CSU anthropologist: History offers lesson about decline of large mammals

Tony Phifer

The effect of the extinctions of numerous large mammal species around 12,000 years ago is still being felt today and could provide a preview of what’s to come as several existing large mammal species find themselves on the brink of extinction.

According to a study led by Anikó Tóth at Australia’s Macquarie University and coauthored by Colorado State University paleoanthropologist Andrew Du, the loss of megafauna such as mastodons, mammoths, saber-toothed cats, ground sloths and others impacted the landscape for surviving species as the last ice age ended. Tóth and Du, along with 17 other international researchers, are part of the Evolution of Terrestrial Ecosystems working group based at the Smithsonian Institution. The results of their study were published in the Sept. 20 issue of Science.

“For decades researchers have debated what caused the great extinction of these large mammals across North America, but our group wanted to look at the effect of those extinctions,” said Du, who joined CSU’s Department of Anthropology and Geography faculty this summer. “It’s very interesting and meaningful work because most of our at-risk mammals today are the larger ones. This study looks at what would happen if these large mammals went extinct.”

Loss of ice age beasts altered ecosystems

Andrew Du, Department of Anthropology and Geography, Colorado State University

Du said plant and animal communities existed in one pattern for hundreds of millions of years, but the demise of the large mammals changed the landscape. Without them, remaining species tended to interact less frequently, making ecosystems less connected and more vulnerable to collapse.

To reach their conclusions, the group analyzed data accumulated over the past several decades, which included fossil records of around 90 species dating to around 21,000 years ago to the present. Once the larger mammals went extinct, smaller mammals such as deer and coyotes tended to keep to themselves rather than interact with other species.

“Regardless of what caused the demise of the large mammals,” said Du, “once that happened, it created a cascading effect throughout the ecosystem that affected all species. Those large mammals were important components of those ecosystems.”

Is history repeating itself?

Du said African elephants are a good modern example of the role large mammals can have in ecosystem impact. Elephants, he said, knock over trees and strip their bark, helping create grasslands. While doing research in Kenya earlier this year, he and other researchers came upon a forest where one previously had not existed – all because elephants had been excluded from the area.

“If you suddenly have a forest where there previously was a grassland, that impacts the entire ecosystem,” he said. “It changes the frequency and impact of fires and alters the way other species utilize the landscape.”

Du said the study should sound a warning as threats to endangered large mammals like elephants, tigers, rhinos and others increase.

“The first thing we have to recognize is that large animals are very important members of these ecosystems,” he said. “This study isn’t the first to show their importance, but it does look at the effect of losing them. Conservation efforts are having a positive impact, but if we lose more of these species it will drastically restructure our ecosystems – and that’s not an ideal scenario.”