Before the arrival of human beings in the Amazon, fires were quite rare. Almost 15,000 years later, the region’s forest cover is reaching a point where it will no longer recover from current levels of deforestation and burning, a destruction that has never occurred in the past 100,000 years. At this rate, the forest will be replaced by a savanna (pasture with few trees) in this century.
It was to this bleak conclusion that biologist Mark Bush of the Florida Institute of Technology arrived in his research “New and recurring tipping points: the interaction of fire, climate change and deforestation in neotropical ecosystems”, published in Anais from the Missouri Botanical Garden in the United States.
Burnings arrived with the man
Analyzing samples of fossilized pollen and charcoal, an indicator of fire, resting thousands of years on the bottom of lakes, Bush mapped about 370 thousand years of paleological history in the region, tracking changes in vegetation over four glacial cycles and the frequency with that the fire was raging through the forest. According to the biologist, fires were almost unknown in the Amazon before the arrival of humans.
“Fire is a transforming agent in Amazonian and Andean vegetation, but it is rare in nature”, says the biologist in his study.
According to Bush, who is the leader of the Florida Tech Conservation Biology and Ecology Program, the first inhabitants of the Amazon have caused relatively minor disturbances in the past 10,000 years – nothing that the forest could not recover.
In decades, only pastures
The changes brought about by global warming and the consequent increasingly drier climate “are combining with deforestation and burning on an increasing scale, creating conditions for vast areas of tropical forest to transition to savannah in a matter of decades “.
If temperatures rise between 1 ° C and 1.5 ° C, the tipping point, when it will not be possible for the forest to recover, will be reached, which is likely to happen by the end of this century. With poor soil, tropical forests need high humidity to survive, as they are not adapted to withstand fire. The constant and increasingly violent burning seasons bring more heat to the region, which becomes drier and less shaded, accelerating the transition.
Regional problem, global effects
For the biologist, “the mortality of trees induced by drought and fire presages an imminent inflection point. Global warming may, in itself, induce it in this century, but if current policies are not interrupted by governments, who turn a blind eye to the destruction of the forest, we may arrive at a moment of no return much sooner “.
The end of the vegetation cover will take with it its immense and still unexplored biodiversity, bringing disastrous changes to the global climate. “Almost all fires in the Amazon are caused deliberately and have become much more frequent in the past 2 years. In addition to the loss of wildlife, the cascading effects of the end of the Amazon rainforest would alter rainfall across the hemisphere. This is not a problem. remote but of global and critical importance for food security “.