In a recently published study, American scientists have established a direct link between the extinction of the megafauna, at the end of the Quaternary, and the massive increase in prairie fires .
The period that begins 50,000 years ago, and ends 6,000 years ago, and which has seen the disappearance – for different reasons, and sometimes poorly explained – of truly iconic species (such as the giant bison or woolly mammoths) , presented an ideal field of observation for scientists.
Thus, they observed how the extinctions spread across four continents for which, in fact, the researchers had enough information. And they found great inequality.
They found that by losing 83% of its megafauna, South America was one of the hardest hit , followed closely by North America, with 68%. On the other side we find Australia (with 44%) and Africa (with 22%).
The Yale University researchers then turned their attention to the Global Paleofire Database, a database containing information on ancient fires, which lists the carbons found in the sediments of certain lakes, something very useful that not only allows dating but also estimating the importance of fires registered in the past.
Thus, they observed that, in most of the 410 sites corresponding to their period, fires increased after the disappearance of large herbivores, regardless of the climatic factor .
Then, breaking down these events by continent, they came across the same list: It was in South America that fire activity ended up experiencing the most growth, followed again by North America and Australia. And lastly, Africa.
The consumption of plants and herbs by herbivores tends to shape the landscapes. And a good example is found in the grazing activity of herds of cows and sheep, which maintain large open spaces because both trees and shrubs do not have time to develop in those areas.
However, if the different herds cannot frequent these spaces, the most common is that they end up becoming forests.
It was what the authors of the aforementioned study, published in the journal Science, found : the disappearance of large herbivores resulted in an accumulation of leaves, grasses and dry wood that, in turn, led to the spread of fires.
In particular, grass fires have increased especially in the prairies . Although they point out that other herbivores, such as mastodons (mammoths and proboscidia, similar to elephants), giant sloths or diprotodons (giant marsupials), which also became extinct during this period, but whose disappearance apparently did not have as much impact on the extent of fires feeding mainly on trees and shrubs.
Not surprisingly, some time ago we knew that the disappearance of large herbivores (those weighing more than 100 kilos) was affecting ecosystems, especially in Africa and Asia.