UC Berkeley researchers find mammal extinction may have affected current ecosystem

Tony Barnosky/Courtesy

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In a study published Monday, researchers, including one from UC Berkeley, discovered that the extinction of large land mammals near the end of the Ice Age had permanent effects on Earth’s ecosystem.

Anthony Barnosky, professor in the campus department of integrative biology and curator of the UC Museum of Paleontology, and Elizabeth Hadly, a Stanford University biology professor, found that the loss of large animals, such as mammoths, is a reason that grasslands are turning into shrubbery and small forests today.

“We didn’t know if this was a permanent or temporary effect,” Barnosky said. “Through looking at fossils, we are determining when big animals went extinct and seeing how that correlates to changing vegetation.”

Many mammals that used to trample and eat vegetation before it would start to pollinate are now extinct, according to the study. Without these animals’ consumption, vegetation was and is spreading through North America at a faster pace, which increases the risk of forest fires, according to Emily Lindsey, a postdoctoral researcher in Barnosky’s laboratory.

“We always assumed that climate change is affecting the changing landscape,” Lindsey said. “But it is really the loss of pressure from big mammals going extinct that is changing the vegetation.”

Large mammals, such as mastodons, ate plants before the plants grew to their full size, and they trampled on vegetation. As a result, these large animals helped keep grasslands from turning into forests, as researchers found by looking at fossils in three regions in North America.

“Fossils that we looked at record the tie between large animals and vegetation,” Hadley said. “The extinction in North America still impacts vegetation. The animals exerted a force that no living animal can.”

The group examined five places in the world where there was evidence of mastodon extinction, including California, Alaska, the Northeastern United States and two areas in South America. While evidence linking extinction of large mammals to changing landscapes was found in North America, none was found in South America.

This is due to the fact that there have never been mammals or mastodons present in those parts of South America. In Argentina, because the climate and soil conditions are not conducive to growing forests, researchers did not find a correlation between the extinction of large mammals and changing landscape, according to Barnosky.

Lindsey said that in the future, they hope to examine more regions in South America, where a tropical rain forest in the continent is already showing a correlation between extinction and changing vegetation on Earth today.

“A lot of large animals are in extinction today or are going to be extinct sooner or later,” Barnosky said. “We will not only lose these species but a lot smaller animals that depend on them. The ecosystem would be disrupted.”

Contact Danwei Ma at [email protected].