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Earth science: The extinction of the world’s largest animals led to an increase in grassland fires


A study finds that the loss of the megafauna grazing on Earth between 50,000 and 7,000 years ago led to a massive increase in grassland fires worldwide.

These large herbivores—which included the famous woolly mammoth, giant bison, and ancient horses—are thought to have become extinct as the climate warmed.

However, experts led by Yale University showed that their loss had spillover effects – with weeds they no longer eat to provide fuel for wildfires.

The team added that their findings highlight the need to consider the role of herbivores when projecting global fire activity now and in the future.

Study finds that the loss of Earth-grazing megafauna – including the woolly mammoth – 50,000-7,000 years ago led to a massive increase in grassland fires worldwide

These large herbivores - such as the famous woolly mammoth, giant bison (whose remains have been photographed) and ancient horses - are thought to have gone extinct as the climate warmed.

These large herbivores – such as the famous woolly mammoth, giant bison (whose remains have been photographed) and ancient horses – are thought to have gone extinct as the climate warmed.

The research was conducted by paleobiologist Alison Karp of Yale University, Connecticut, and colleagues.

“These extinctions led to a series of consequences” — among them, she explains, the collapse of predators and the loss of fruit trees that depended on large herbivores to disperse their seeds.

“Studying these influences helps us understand how herbivores shape today’s global environment,” she explained.

The researchers wondered whether — given that the loss of giant herbivores would likely lead to an accumulation of dry grass, leaves and wood — this might lead to a temporary increase in fire activity.

In their study, the experts compiled a list of large mammals now lost and approximate dates when they became extinct across four continents.

Their analysis indicated that South America lost the largest number of grazing animals (83 percent of all species), followed by North America (68 percent), Australia (44 percent), and then Africa (22 percent).

Next, the team compared this data with records of past wildfire activity as recorded by the presence of charcoal in lake sediments from 410 sites worldwide.

Not only did this reveal increased wildfire activity following the extinction of megafauna – but that the Americas, which lost more grazing animals, saw greater increases in fire levels than Australia and Africa, where changes were smaller.

According to Dr. Karp and her colleagues, grasslands around the world have been altered by the loss of herbivores, the resulting fires and the loss of grazing-tolerant weeds. It took time for the new pastoralists, including livestock, to adapt to the new ecosystems.

However, the loss of large transversal species – such as mastodons, giant sloths and Australian diprotodons, all of which feed on shrubs and trees – has not been found to be associated with a similar increase in bushfires.

In their study, the experts compiled a list of large mammals now lost and approximate dates when they became extinct across four continents — and compared this data with records of past wildfire activity as recorded by the presence of charcoal in lake sediments from 410 sites worldwide, shown

In their study, the experts compiled a list of large mammals now lost and approximate dates when they became extinct across four continents — and compared this data with records of past wildfire activity as recorded by the presence of charcoal in lake sediments from 410 sites worldwide, shown

Not only did the analysis reveal increased wildfire activity following the extinction of megafauna (shown) - but that the Americas, which lost more grazing animals, saw greater increases in fire levels than Australia and Africa, where changes were smaller.

Not only did the analysis reveal increased wildfire activity following the extinction of megafauna (shown) – but that the Americas, which lost more grazing animals, saw greater increases in fire levels than Australia and Africa, where changes were smaller.

The team said the findings show how we should consider the role of herders of wild animals and livestock in mitigating wildfires, particularly given climate change.

“This work really highlights how important pastoralists are in shaping fire activity,” said paper author and ecologist Carla Staver, of Yale University.

“We need to pay close attention to these interactions if we are to accurately predict the future of fires.”

The full results of the study were published in the journal Science.

WHAT DO WE KNOW ABOUT ANCIENT MEGAFAUNA?

The Earth was once inhabited by a variety of gigantic animal forms that are recognizable today in the smaller forms taken by their ancestors.

They were quite large, usually over 88 pounds (40 kg) and generally at least 30 percent larger than any of their surviving relatives.

There are several theories to explain this relatively sudden extinction. The main explanation for what was around him was that this was due to environmental and ecological factors.

Almost finished by the end of the last ice age. Megafauna is believed to have initially emerged in response to icy conditions and became extinct with the advent of warmer climates.

In the temperate zone of Eurasia and North America, the extinction of megafauna ended simultaneously with the replacement of the vast surrounding tundra a vast area of ​​forests.

Glacial species, such as mammoths and woolly rhinos, were replaced by animals that are better adapted to forests, such as elk, deer, and pigs.

Reindeer and Caribou retreated north, while horses moved south to the steppes of Central Asia.

All this happened about 10,000 years ago, despite the fact that humans colonized North America less than 15,000 years ago and non-tropical Eurasia nearly a million years ago.

Worldwide, there is no evidence that indigenous peoples systematically hunted or excessively killed megafauna.

The largest regularly hunted animal was the bison in North America and Eurasia, yet it survived about 10,000 years until the early 20th century.

For social, spiritual and economic reasons, First Nations peoples reaped the game in a sustainable way.



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