Climate change poses a unique set of threats to the world’s forests. Forests are vital for ecosystems, water and nutrient cycles, and carbon management, so dying trees are a worrying prospect. And increased temperatures and droughts certainly have the potential to kill trees.

But a paper in this week’s PNAS suggests that the increased CO₂ and humidity that will accompany climate change may go some way toward offsetting the risks to forests—and identifies which forests are likely to fare better and worse.

Feed the tree

What kills a tree? As with humans, the options are endless, but climate change creates some specific risks. Decreasing annual rainfall in certain regions is an obvious problem, but it’s also about when the rain falls, not just how much of it does. Drought in the growing season is a bigger problem than at other times of year. Higher temperatures also mean that trees lose more water from their leaves. On the other hand, higher humidity and more CO₂ in the air allow trees to operate more efficiently. That might allow them to compensate for drought and heat.