Fellows in the News

Forests could actually turn into a source of CO2, according to a study that paired climate forecasts with an analysis of records on more than two million trees across North America.

Scientists have considered forests a potential barrier to climate change, since plants on land take up about 25 percent of our carbon dioxide emissions. As trees in colder areas are exposed to warmer temperatures and more CO2 emissions, they will grow faster and absorb more emissions, helping to mitigate the effects of a primary greenhouse gas, the theory goes. 

But, in an alarming twist, global warming is likelier to limit forests' capacity for absorbing emissions in many parts of the continent, a study released today in the journal Ecology Letters finds. After combining climate projections with the tree records, researchers found no evidence for the boreal greening hypothesis. In fact, they found a risk of a negative feedback loop, as trees in their model reacted poorly to warmer temperatures due to drought and other disturbances. 

That means as trees die faster than they can take up CO2 emissions, releasing trapped carbon, forests could become a net source of carbon, accelerating climate change. The study found that we could reach such a tipping point as early as 2050. 

“It’s one more piece of evidence that this is a serious problem and it’s going to take a real serious global coordination to stop it,” said Noah Charney, the study's first author and a postdoctoral research associate in the University of Arizona’s Department of Ecology and Evolutionary Biology. “There isn’t necessarily going to be some balance that’s going to keep us in check.”

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