Tropical Forests Sensitive to Global Warming: A Study

Tropical forests are intensely sensitive to climate change, causing them to produce more flowers in response to only slight increases in temperature, according to a new study conducted by the University of California, Santa Barbara's National Center for Ecological Analysis and Synthesis (NCEAS).

Published in the journal Nature Climate Change, the study, which used a new globally gridded satellite dataset, examined how changes in temperature, clouds and rainfall affect the number of flowers tropical forests produce.

"This study is an inspired example of integrating diverse existing data to do something never imagined when the data were originally collected," explained Stephanie Hampton, deputy director of NCEAS. "Flowers were probably not what NASA scientists were thinking of when they archived these cloud data."

A forest's flower productivity is a measure of its reproductive health and overall growth, the researchers explained, which in turn can have a direct effect on the overall environment.

"Tropical forests are commonly thought of as the lungs of the Earth and how many flowers they produce is one vital sign of their health," said Stephanie Pau, who conducted the research as part of a Forecasting Phenology working group while she was a postdoctoral associate at NCEAS. "However, there is a point at which forests can get too warm and flower production will decrease."

Pau led a team of international researchers who studied seasonal and year-to-year flower production in two contrasting tropical forests: a seasonally dry forest on Barro Colorado Island, Panama, and a rainforest in Luquillo, Puerto Rico.

In doing so, they found that, of all the variables they examined, the data indicated that clouds mainly had an effect on short-term seasonal growth while longer-term changes in these forests appeared to be a result in temperature changes. Ultimately, the amount of sunlight reaching tropical forests due to varying amounts of cloud cover is an important factor, the researchers argue - just not the most important when it comes to flower production.

According to Pau, both sites still appear to respond positively to increases in light availability, yet temperature was the most consistent factor across multiple time scales.

"With most projections of future climate change, people have emphasized the impact on high-latitude ecosystems because that is where temperatures will increase the most," Pau said. "The tropics, which are already warm, probably won't experience as much of a temperature increase as high-latitude regions. Even so, we're showing that these tropical forests are still really sensitive to small degrees of change."