Listening to forests, researchers establish their limits to heat and drought

Forests are seen as those that could help us limit global warming. But researchers warn us today. There comes a time when too much — too hot or too dry — is too much. And the very survival of the trees is then threatened.

“It is as if we had given the floor to the forests of the world »tell of researchers from an international team. How? ‘Or’ What ? By studying precisely georeferenced forest dieback events. In 675 locations around the world. To forget no wooded continent. Since 1970. And what have these forests yielded? That sometimes, too much… it’s too much!

By relating dieback events to climatic data, the researchers were able to establish the conditions for heat and drought most likely to put our forests at risk. They are linked to climatic extremes intensified. And climate models show that these extremes will become more frequent by 22% under a global warming of 2°C compared to the pre-industrial era. 140% below 4°C warming! Conditions that would double the frequency of dieback events.

Bad news for carbon storage

The researchers give the example of a temperate forest in Mexico. They note that for some years the season dry and hot from March to May is even drier. And even hotter than ever. What induce a stress for trees before the onset of the rainy season. A situation further amplified by the phenomenon La Nina which led, in 2021, to the loss of more than 8,000 mature trees, killed by bark beetles in the biosphere reserve of monarch butterfly in the center of the country.

Researchers are now stressing the importance of better understanding how not the hot can become ” too hot “ and the dry ” too dry “ for forests. Because beyond the fact that a dead tree can no longer capture carbon — and thus help to limit global warminganthropogenic — a dead tree gradually releases carbon. As it decomposes. And mortality events could thus wipe out the gains predicted by those who hope to rely on trees and plants to sequester some of the excess carbon we emit.