Tropical forests and global warming

Print edition : April 19, 2013

TROPICAL forests are less likely to lose biomass in response to greenhouse gas emissions over the 21st century than previously thought, according to a study published in Nature Geoscience, the most comprehensive assessment yet of the risk of the gradual death of tropical forests due to climate change. The results have important implications for the future evolution of tropical rainforests, including the role they play in the global climate system and carbon cycle.

The research team included climate scientists and tropical ecologists from the U.K., the U.S., Australia and Brazil and was led by Chris Huntingford of the Centre for Ecology and Hydrology in the U.K.Using computer simulations with 22 climate models, the scientists explored the response of tropical forests in the Americas, Africa and Asia to climate change caused by greenhouse gases. They found loss of forest cover in only one model, and only in the Americas. The largest source of uncertainty in the projections, they found, were the differences in how plant physiological processes were represented in the models. Although this work suggests that the risk of climate-induced damage to tropical forests will be relatively small, the scientists have also emphasised that considerable uncertainties remain in defining how ecosystems respond to global warming.

“The big surprise in our analysis,” said Huntingford, “is that the uncertainties in ecological models of the rainforest are significantly larger than uncertainties from differences in climate projections. Despite this, we conclude that based on current knowledge of expected climate change and ecological response, there is evidence of forest resilience for the Americas, Africa and Asia.”

“While these new results suggest that tropical forests may be quite resilient to warming, it is important also to remember that other factors not included in this study, such as fire and deforestation, will also affect the carbon stored in tropical forests. Their impacts are also difficult to simulate,” said co-author David Galbraith of the University of Leeds.