FSU researcher discovers forest canopies are warmer than previously thought

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

Stéphanie Pau, 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 optimum 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 earth, she said.

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

She added: “The global temperatures that are livable for us are very closely related to the amount of carbon dioxide that forests can remove from the atmosphere.”

The study included the use of state-of-the-art thermal camera monitoring technology that measured temperatures every five minutes across a network of sites. Although it has long been known that leaf temperature often differs from air temperature, most previous studies have come from experiments on individual leaves.

“Previously it was thought that tree leaves cooled by transpiring water when the air temperature got too warm for optimal photosynthesis,” Pau said. “Our study shows that this is not happening. Leaves and treetops are almost always warmer than the air temperature, and they do not cool when above their optimum temperatures.

The study highlights the importance and precariousness of the world’s forests, she said.

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

The authors of the article 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 Institute for Tropical Research, Ames Research Center, Meteorology Section Canadian Forces Base, Trenton.