Droughts, fires… Forests could absorb less carbon

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Due to the drought, in the Vosges forest (here in Sewen, in 2019) spruces and firs are dying. – © Margaux Velikonia / Reporterre Due to the drought, in the Vosges forest (here in Sewen, in 2019) spruces and firs are dying. – © Margaux Velikonia / Reporterre Today, forests are the safest way to store carbon. By absorbing large amounts of atmospheric carbon through photosynthesis, their role as carbon sinks is gaining them increasing attention in the name of nature-based solutions. But a study published in Science on September 2 shows that, disrupted by climate change, forests may not play the role expected of them. To assess the risks facing the world’s forests in the 21st century, the international study combines the results of several scientific approaches, from carbon flow modeling to direct observations of forest evolution. The synthesis shows that some approaches are more optimistic than others. “The results on carbon storage [à partir de modèles basés sur les échanges de carbone] they are probably too optimistic. Methods based on satellite observations tend to show more risks,” says the first author of the study William RL Anderegg, a researcher at the University of Utah. The American researcher tells Reporterre that the former overestimate the benefits of increasing atmospheric carbon. A higher concentration of CO2 favors plant growth and thus contributes to increased carbon storage. But provided that the forests are in good condition. However, droughts, heat spikes and fires directly threaten the world’s forests. Damages little taken into account by these early models. “A much higher level of uncertainty” Other approaches, on the other hand, look at how forests will evolve under the effect of global warming and the increase in extreme events Scientists know, for example, that the change in the biological rhythm of plants, with longer growing seasons contributing to increased stress hydric, weakens the vegetation. Certain species are expected to disappear in regions where climatic conditions are too far removed from their current habitat. A study published in Nature last February thus showed the evolution of the distribution of forest species on the planet under the effect of global warming. The drier regions of the Amazon are at high risk. Here in the region of Manaus (Brazil), in 2005. Wikimedia Commons/CC BY 3.0/James Martins Another key conclusion of the Science study, the sometimes contradictory results of the models. “The level of uncertainty, especially between different approaches, is much higher than I expected,” acknowledges William RL Anderegg. A conclusion that shows that knowledge to predict the consequences of climate change on forests remains incomplete. However, some regions (the North American forests, the drier parts of the Amazon, and the southern boreal forests) are at particularly high risk in the coming decades, regardless of the methods and scenarios. These areas, already located on the edge of large areas of distribution, are particularly vulnerable to global warming. “The western forests of North America are particularly dry, which has already led to significant tree mortality under the effect of climate change,” the researcher emphasizes. 📨 Subscribe for free newsletters Subscribe in less than a minute to receive a selection of articles published by Reporterre by email, either daily or weekly. Subscribe After this article Climate Climate change threatens the carbon storage capacity of tropical forests Comments September 2, 2022 at 10:01 am, Updated September 2, 2022 at 2:40 pm Reading Time : 3 minutes

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