The extensive northern forests of Canada, Alaska and Siberia are about to fundamentally change their tree density because of climate change. According to a new study led by researchers from Wageningen University & Research and published in the Proceedings of the National Academy of Sciences, this change will increase the risk of forest fires. The research team explored 20 years of tree cover data from satellites to model future shifts.
Boreal forests encircle the cold, northern regions of our planet. They host a diverse set of species, regulate global climate by storing huge amounts of carbon in the trees and soils, and provide for the livelihoods of millions of people. However, within decades, climate warming is now rapidly changing the conditions under which boreal forests have fulfilled their important roles for millennia. Understanding how boreal forests may change in the future is therefore key.
Because boreal trees grow slowly, it takes some time to see changes in the forest. “This time lag could keep the forests in a state that doesn’t match the changing climate,” explains Ronny Rotbarth, lead author of the new study, which he carried out as a Ph.D. candidate at Wageningen University & Research.
“Forests growing at the southern boreal distribution range may not be able to maintain the current number of trees as the climate becomes drier and warmer. Therefore, they may become less dense. Other forests, in the cold north, could support more trees as conditions warm up, and in fact become denser than the forests we currently find there.”
Past changes offer glimpse into the future
Future changes in ecosystems, such as boreal forests, are typically projected by complex simulation models. In the new study, the researchers used an alternative innovative approach. “By examining two decades of tree density from space, we explored whether past changes could hint at the future state to which the forests may be shifting,” says Egbert van Nes, co-author of the study. The researchers used the changes in tree density during that time to project forest conditions until the year 2100.
