Tropical forests are losing their ability to absorb carbon dioxide emitted into the atmosphere, according to a 30-year study of hundreds of thousands of trees.
Research led by the British University of Leeds, published today in the journal Nature, reveals that tropical forests have started to move from carbon dioxide deposits to emitters of that gas that causes the greenhouse effect.
Tropical forests sequester carbon, removing it from the atmosphere and depositing it in trees, thus slowly combating climate change, but new data indicate that this capacity reached its peak in the 1990s and has been declining.
The team of scientists analyzed three decades of tree growth and death in 65 virgin tropical forests in Africa and the Amazon and came to the conclusion that in the past decade, the forest’s carbon sequestration capacity has decreased by a third, which is because more trees die and the forest loses the ability to capture it.
More than 100 institutions collaborated in the research that shows for the first time on a large scale that a worrying loss is already occurring in a model that was normally considered safe in the coming decades.
The increase in carbon dioxide in the atmosphere favors the growth of trees, “but each year this effect is being offset by the negative impacts of high temperatures and droughts that delay the growth of trees and can kill them,” said the researcher and lead author of the study, Wannes Hubau, from the University of Leeds, in northern England.
“Combining data from Africa and the Amazon, we started to understand why these forests are changing, mainly because of carbon dioxide levels, temperatures, droughts and forest dynamics”, he added.
What the data shows is “a long-term future decline” in Africa and that the Amazon “will continue to weaken rapidly” until it becomes a carbon source in the mid-2030s.
In the 1990s, virgin tropical forests removed about 46 billion tonnes of carbon dioxide from the atmosphere, dropping to 25 billion tonnes in the 2010s.
What has been lost is the equivalent of what France, Germany, the United Kingdom and Canada jointly emit for ten years into the atmosphere through the consumption of fossil fuels.
As a percentage, from 17% of the emissions caused by human activity withdrawn in the 1990s, it went up to just 6% twenty years later.
Forests have lost 33% of their capacity to retain carbon dioxide and the area of intact forest has decreased by 19%, while emissions have increased by 46%.
Researcher Simon Lewis, from the geography faculty at Leeds University, noted that “intact rainforests remain a vital carbon scavenger, but without policies to stabilize the Earth’s climate it is only a matter of time before they are no longer capable of absorbing carbon dioxide “.
Losses first started in the Amazon in the mid-1990s, while in Africa they started fifteen years later.
The difference is explained by the fact that Amazonian forests are more dynamic than African forests and are more subject to strong climatic impacts, with higher temperatures, with rapid rises, and more severe and frequent droughts.
The authors point out that tropical forests are still huge carbon reservoirs, storing 250 billion tons in the trees alone, which is equivalent to 90 years of global emissions generated by the consumption of fossil fuels.
Cameroonian researcher Bonaventure Sonké, from Yaounde I University, said that “African countries and the international community will have to invest seriously in preparing for the current impacts of climate change on tropical regions”.
Another scientist at the University of Leeds, Oliver Phillips, added that it is necessary to support the work of scientists from Africa and the Amazon, whose “capabilities and potential have been underestimated”.
“It will be up to the next generation of African and Amazonian scientists to watch over these remarkable forests to help manage and protect them, “he said.
The most urgent dangers are deforestation, the timber industry and fires.