Treetop species threatened by rising temperatures among forest canopies

When researchers surveyed temperature changes inside the forest canopies on Panama's Barro Colorado Island, they found the treetops regularly registered temperatures 7 degrees Celsius hotter than the maximum air temperature.

The survey results -- detailed in the journal Ecosphere -- suggests tropical forest canopies will experience 1.4 degrees Celsius of warming for every 1 degree Celsius rise in the local air temperature.

Scientists recorded temperatures in the canopy every five minutes for several months. The data showed treetop temperatures are highly variable. As temperatures rise, scientists suggest tropical canopies could not only get warmer, but host even more extreme temperature fluctuations.

Models suggest higher canopy temperatures could accelerate photosynthesis up to a certain point, but that the treetop's metabolic productivity slows if temperatures rise too much.

"Tropical forests are among the most productive places on Earth -- they account for about 30 percent of terrestrial productivity," Stephanie Pau, an assistant professor in the geography department at Florida State University, said in a news release. "These forests are vulnerable to climate change and climbing temperatures."

Researchers used an advanced thermal imaging system to plot heat maps of the Panamanian canopies, revealing which parts of the treetops heat and cool down the fastest. The data showed evergreen canopies cooled down faster than deciduous treetops, while flower clusters remained cooler than tree bark.

How global warming alters components of the treetop microclimate could affect which species are impacted.

"There are so many different organisms that use and partition the canopies in different ways," Pau said. "For example, ant species in tropical forests are extremely sensitive to bark temperatures. The diversity of canopy dwelling species will be affected by canopy temperatures -- and it's not just how hot it will get, but it's also the temperature variability within a canopy."

While previous research has shown microclimates could offer respite to some species, the latest findings are reminder that species that already live in microclimates or small niches are especially vulnerable to environmental change.