When it comes to saving the planet from the ravages of climate change, protecting forests is a high priority for almost everyone. But at the current rate of warming, forests may not be able to adapt quickly enough to remain healthy, according to a study published Monday in the journal Proceedings of the National Academy of Sciences. This has adverse consequences for everything from carbon storage to biodiversity. The study looked at forests in the western US and found that they are evolving to cope with higher temperatures – something scientists call "thermophilicisation" – by becoming increasingly dominated by trees better able to tolerate heat and drought stress. However, the researchers found that the speed of this transformation "lags behind climate change by a factor of ten". This creates a situation in which, according to the document, "forest trees are increasingly mismatched with their environment." This means trees are more likely to die or be susceptible to fire or insect attack. Researchers from the University of California, Berkeley and the US Forest Service analyzed the composition of approximately 50,000 forest plots in western states over 10-year periods. The USFS has spent decades building an inventory of trees on these lands to monitor long-term changes, and researchers have used that data and then mapped localized climate change data onto it. "Ideally, you would see an individual relationship between the thermal tolerance of trees and warming," said Kyle Rosenblad, Ph.D. candidate at the university and lead author. While he and the team found that trees with greater tolerance for warmer temperatures and drier weather, such as California juniper, are indeed gaining dominance, climate change is outpacing those adaptations. Equally troubling, Rosenblad said, is how the ratio of trees is changing. New species do not come to forests. Instead, the composition is changing mainly because established species that prefer cooler, wetter conditions—such as Douglas fir—die or are weakened and attacked by insects. This could lead to large-scale ecological changes over centuries or even decades. "Places that are forested today may only be able to support grasslands," Rosenblad said. "Try as we may, we may not be able to stop it."

(Leslie Kaufman)