Our forests are precious. From multiple points of view. They help us limit global warming by storing carbon, for example. But they also suffer from this same warming. Some more. Others a little less. It will soon be important to target which ones to focus our regeneration efforts on.
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On the California side, a period of megadrought which lasted three years, between 2012 and 2015, damaged the ponderosa pine forests, decimated by an invasion of small bark beetles, pine beetles. More broadly, nearly 130 million trees ofspeciesspecies different died. Of the Los Alamos National Laboratory researchers (United States) announce today that these forests will probably not regain their previous density for a century. A problem for the storage of carbonecarbone. But the good news is that these forests now seem protected from other attacks, precisely because of their low density.
The interactions are complex, explain the researchers. With global warming, bark beetles are growing faster. Fewer of them diewinterwinter. With the stressstress due to droughtsdroughts that multiply, the most populated forests also become more susceptible to attacks by beetles. And it is only once the density of forests has been drastically reduced by bark beetles that said forests become more resistant again. A phenomenon to be taken into account when planning to regenerate forests.
Of the University of Utah researchers (United States) confirm this. According to them, the regions of the United States most at risk of losing forest carbon through wildfires, climate stress or damage from insectsinsects — three causes made more frequent in the context of climate change — are where many carbon offsetting projects through forest cover have been implemented. “It is really urgent to update these projects”comments William Anderegg, lead author of the study, in a communiqué.
Complex interactions to be specified
He and his team have mapped out possible futures for U.S. forests in the face of climate change by not only drawing on historical data, but also using machine learning to identify climate niches that species of trees prefer the most and thanks to complex models that include the interactions between the ecosystem and theatmosphereatmosphere. If these different models showed some divergences, they also provided some points of convergence.
Thus, according to the researchers, the country’s forests should, by the end of the XXIe century, store between 3 and 5 billion tons of additional carbon. It’s good news. Although it should be noted that, without global warming, the figure would have risen to nearly 9.5 billion tonnes.
Researchers also report that a large number of carbon offset forestry projects — planting trees to capture carbon from the atmosphere — especially in the southeast and west coast of the United States are aimed at ‘failure. Before the end of the century, reforested areas will emit carbon — through forest fires or insect attacks — instead of storing it.
But many questions still remain unanswered. To what extent does the increase in CO concentrations2 in the atmosphere could benefit plants and trees and help them grow more? What are the real effects of fires, climatic stress and insects on tree mortality? Or, how will the biomes move? Researchers should respond as soon as possible. In the meantime, they recall that “Combat climate change as soon as possible and move to a low-energy future. issueissue carbon massively reduces the risks that forests are likely to face and increases the potential benefits that we could derive from those same forests”.
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