Loss of ancient grazers triggered a global rise in fires

Woolly mammoth. Tracy O is pictured via Wikimedia Commons.

The woolly mammoth, giant bison, and ancient horses were extinct from 50,000 years to 6,000 years ago. A new study published in the journal Science shows that the loss of these species caused a dramatic increase in fire activity in the world's grassland.

Yale scientists collaborated with the Utah Natural History Museum to create lists of extinct large mammals and their approximate dates of extinction. South America lost the most grazers, followed by North America. The losses were higher than in Australia and Africa.

They compared the findings with the records of fire activity in the lake. They used charcoal records from 410 global sites to show that fire activity increased after the extinctions. South America, then North America, saw larger increases in fire extent, whereas Australia and Africa saw little change in grassland fire activity.

Allison Karp is a researcher in the Department of Ecology & Evolutionary Biology at Yale. The effects of herbivores help us understand global ecology today.

Widespread megaherbivores had major impacts on extinction, from predator collapse to the loss of fruit-bearing trees. The authors wondered if there was an increase in fire activity in the world's ecosystems due to a build up of dry grass, leaves, or wood. Grass- fueled fires increased in the grassland.

Mastodons, diprotodons, and giant sloths, which foraged on shrubs and trees in wooded areas, went extinct during the same period, but their losses had less impact on fires in wooded areas.

The loss of herbivores and increase in fires resulted in the transformation of the grassland. New grazers, including livestock, adapted to the new environment.

The authors said that scientists should consider the role of livestock and wild animals in climate change. Staver said that the work highlights how important grazers are for shaping fire activity. If we want to accurately predict the future of fires, we need to pay close attention to these interactions.

The Global response of fire activity to late Quaternary extinctions was written by Allison Karp. www.science.org/doi/10.1126/science.abj1580

Science journal information.

The loss of ancient grazers triggered a global rise in fires.

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