NASA / JPL CalTech

Droughts are hitting us harder, and they’re only going to keep on coming. But how do you know if your trees can make it through a severe drought? Now there’s a way to find out before the drought hits.

Obviously, some species of trees need more (or less) water than others. But scientists didn’t know why, when an unexpected dry spell hit, some species seemed to be able to weather the (lack of) storm, while others died off en masse. So researchers at the University of Utah undertook a survey of the available drought data to see what traits the survivors had in common. The results have just been published today in the Proceedings of the National Academy of Sciences.

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It’s not so much a question of how much water a species of tree does or doesn’t take up. Rather, it comes down to how well the tree transports that water. The less readily available the water, the harder the tree works to pull it up—and some trees simply break down under all that pressure.

Trembling aspens in Arizona, not making it through the drought / William Anderegg

“It’s a little bit akin to a tree heart attack,” lead researcher William Anderegg explained in a statement. “You can actually hear this on a hot summer day if you stick a microphone up to a tree—you can hear little pings and pops as these pipes get filled with air.”

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So what can we do with this new knowledge? We can start to change which trees we’re planting and cultivating. There’s already a move towards fostering plants that need less water, especially in areas like California and Texas that have been hit by long, multi-year droughts. But we’re also going to need to look for trees and other plants that are good at weathering stress in general.

The droughts that we’re seeing now are exceptional not just because of their duration, but because they’re often sandwiched in with other extreme weather events, including storms and hot temperatures that add further stress to plants. If we want to see trees survive climate change, we’re going to need to cultivate the strongest ones we can find.