Biologist Anthony Ambrose climbs the world’s largest trees, but he doesn’t do it for the endorphin rush. The University of California-Berkeley researcher studies how drought and climate change affect forest ecosystems—and right now, he’s concerned about how the state’s sequoia trees are faring under California’s ongoing drought.

Ambrose and his team of researchers check on the trees by measuring their water status, a.k.a. how much water is available for them to continue to function and grow. To do this, the biologist needs to take samples from the trees’ crowns, so he scales the 300-foot sequoias in the name of science.

“As water moves up the tree it’s fighting gravity and friction and the top of the tree is going to be the most stressed part of the tree. So in order to get a really good idea of how stressed they are, we need to go to the tippy top,” Ambrose explains.

Learn more about Ambrose’s research in the video above, courtesy of Great Big Story.

[h/t Great Big Story]

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