American scientists have established a direct link between the extinction of the megafaune at the end of the quaternary and the massive increase of the meadow lights.
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The multiplication of megafeux in recent years has made fire science a booming discipline. How to confront them? How to prevent them? A team from the University of Yale published on Thursday, November 25, in the journal Science, a study that promises to arouse serious debate. In trying to pierce the cause, she has not scrutinized recent disasters in California or Australia. She chose to look at the distant past. And its conclusion is without appeal: the meadow fires have been fed by the disappearance of large herbivores.
“For a long time, we have known that large herbivores eat enough plants to transform the vegetable structure, recalls Allison Karp, researcher in the prestigious university and first audience of the study. It had led to The hypothesis that they could also modify the behavior of the fires. “The mechanism seemed pretty natural: less large gravoists causes a biomass accumulation that will turn the first fire to the brazier. Some studies conducted locally, in the Tanzanian plains of Serengeti or South Africa, pleaded in this direction. “We wanted to test this idea to the largest possible scale, that of the continent through the geological time”, continues the ecologist.
The period opening 50,000 years ago and interrupted 6,000 years ago, which saw disappear
– For various reasons and sometimes poorly explained – iconic species such as woolly mammoth, giant bison or ancient horses, had an ideal observation field. The researchers followed the trajectory of the 302 species of large herbivores of the end of the quaternary. They watched how the extinctions had spread over four continents for which they had enough information and noted great inequality. By losing 83% of his megafauna, South America paid the heavier tribute, followed by North America (68%). Australia (44%) and, above all, Africa (22%) were much more savvy.
The researchers then diven their attention into the Global Paleofire Database, the ancient fire database. The coals found in sediments of some lakes are listed, which allow to date but also to estimate the importance of the fires of the past. On the essence of the 410 sites corresponding to their period, they found that everywhere the activity of the fires increased after the disappearance of herbivores – regardless of the climate factor. By then distributing these events by continent, the same palmaresis appeared: it is in South America that fire activity has experienced the greatest growth, followed by North America, Australia and Africa.
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