United States. – Loss of ancient herbs caused global increase in fires

Madrid, 25 (Europa Press)

The extinction of many of the world’s largest animals between 50,000 and 6,000 years ago, including iconic herbivorous species such as the woolly mammoth, giant bison and ancient horses, dramatically increased fire activity in the world’s grasslands, a According to the new study led by Yale University in the United States, and published in the journal Science.

In collaboration with the Utah Museum of Natural History, Yale scientists compiled a list of large extinct mammals and estimated dates of their extinction on four continents. The data showed that South America was the one that had lost the most species (83% of all species), followed by North America (68%). These losses were significantly higher than in Australia (44%) and Africa (22%).

They then compared these results with records of fire activity revealed in lake sediments. Using charcoal records from 410 locations around the world, which provide a historical record of regional fire activity on all continents, they found that fire activity increased after the megafires were extinguished.

The continents that lost the most herbivores (South America and later North America) showed greater increases in fire range, while the continents with the lowest extinction rates (Australia and Africa) had hardly any increase in grassland activity. There has been a change. Fire

“These extinctions triggered a cascade of consequences,” explains Allison Karp, a postdoctoral associate in the Yale Department of Ecology and Evolutionary Biology and author of the paper. “Studying these effects helps us understand how herbivores currently shape global ecology”.

The mass extinction of megaherbivores had a major impact on ecosystems, ranging from the decline of predators to the loss of fruit trees that previously relied on herbivores for dispersal.

But Karp, an associate professor of ecology and evolutionary biology in the Yale College of Arts and Sciences, and lead author Carla Staver wondered whether increased fire activity in the world’s ecosystems, particularly dry grass, was due to the accumulation of leaves. Wood due to the loss of reason or giant herbivores. He found that the grass fire had increased in the valleys.

However, Karp and Staver note that many species of ancient explorers – such as mastodons, diprotodons and giant sloths, which fed on shrubs and trees in wooded areas – also became extinct during the same period, but their loss of forest. had little effect on the fire. ,

Grassland ecosystems around the world were changed after the loss of grazing tolerant grasses due to the loss of herbivores and increased fires. New herders, including livestock, eventually adapted to the new ecosystem.

Therefore, scientists should consider the role of grazing cattle and wild herders in mitigating fires and climate change, according to the authors.

“This work highlights the importance that shepherds can have in determining fire activity,” says Stever. “We must pay close attention to these interactions if we are to accurately predict the future of fires.”