FSU researcher finds forest canopies are warmer than previously thought

Stephanie Pau, an associate professor in the Department of Geography
Stephanie Pau, an associate professor in the Department of Geography.

A study by a Florida State University researcher finds that temperatures in forest canopies are higher than previous estimates, threatening forests’ vital role in mitigating global warming. 

Stephanie Pau, an associate professor in the Department of Geography, was part of a team whose study was published in Proceedings of the National Academy of Sciences. 

Pau said leaves have optimal temperatures at which they capture carbon from the atmosphere. And as carbon dioxide fuels rising global temperatures, forests remain the most important part of the carbon cycle on land, she said. 

“The implications of our study are that with greater warming in the future, tree canopies will not cool as much as we thought they will, and this means they may sequester less carbon from the atmosphere.” 

She added: “Global temperatures that are livable for us are very closely tied to how much carbon dioxide forests can remove from the atmosphere.” 

The study included the use of cutting-edge thermal camera monitoring technology that measured temperatures every five minutes across a network of sites. While it’s long been known that leaf temperatures often differ from air temperatures, the bulk of previous studies came from experiments on individual leaves. 

“Previous thinking was that tree leaves will cool themselves by transpiring water when air temperatures get too hot for optimal photosynthesis,” Pau said. “Our study shows that this is not happening. Leaves and tree canopies are almost always hotter than air temperatures, and they are not cooling themselves when they are above their optimal temperatures.”  

The study underscores the importance and precarity of forests around the world, she said. 

“Forests play such an important role not just as habitat for biodiversity but they play an important role in keeping our planet at livable temperatures,” Pau said. “We need to work to protect them.” 

Authors on the paper were from: Northern Arizona University, University of Colorado, Princeton University, University of California Irvine, Oregon State University, University of Pennsylvania and University of California Santa Barabara, Los Alamos National Laboratory, Smithsonian Tropical Research Institute, Ames Research Center, Meteorology Section Canadian Forces Base, Trenton.