By Amrith Ramkumar
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…
…Carbon storage on land has long posed a central question for climate change scientists, said David Archer, a professor of geophysical sciences at the University of Chicago who studies global warming. Archer, who wasn’t involved in the study, said he agreed with the researchers’ conclusion: Even though some forests currently store carbon, and will continue to do so as temperatures rise in the future, it’s unclear how long that effect will last before warming leads to negative responses.
There are significant challenges in modeling change in forests and forecasting responses to climate conditions that haven’t been seen before. Nonetheless, Archer said, the study adds to evidence that emissions need to be monitored, especially when considering the impact climate change could have on carbon stored in soil.
“If you count both sides of the land equation, I would not be at all surprised for carbon to start emerging rather than disappearing from land in response to climate in the future,” Archer said. “That just seems to be inevitable to me.”
Read the full story via Bloomberg…