Panama City, Panama - For more than a century humans have been changing the composition of the world's atmosphere through the burning of fossil fuels, agriculture, and other activities. The resulting climate changes may already be having far-reaching impacts on tropical forests. A symposium at the 2002 meetings of the Association for Tropical Biology, hosted by the Smithsonian Tropical Research Institute (STRI), Panama, examined the evidence for these changes and their implications for the future.

Organized by Yadvinder Mahli of the University of Edinburgh and Oliver Philips of the University of Leeds, the symposium included 12 presentations and four general discussion sessions. A selection of some of the results follows.

Yadvinder Mahli provided an overview of ongoing climate changes as a result of increasing carbon dioxide and other greenhouse gases in the atmosphere. Since the mid-1970s all tropical forest regions have warmed, although with regional variation in intensity. There has been even more regional variation in precipitation, but there appears to have been an overall global decline. However, no global trend in dry season intensity has been detected.

Data analysis and models have suggested that increased temperature and atmospheric CO2 will increase the amount of carbon stored by tropical forests by stimulating tree growth. Deborah Clark of the La Selva Biological Station, Costa Rica, re-evaluated the evidence to suggest that tropical forests may not be carbon sinks after all, but instead end up contributing even more carbon dioxide to the atmosphere as temperature rises. Data from La Selva show a strong negative correlation between tree growth and higher temperatures. Temperatures experienced by canopy leaves may be close to the point at which respiration exceeds photosynthesis so that net production of CO2 results. Positive feedback between higher temperatures and CO2 production by tropical forests could be catastrophic by resul
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Contact: George Angehr
angehrg@tivoli.si.edu
011-507-212-8024
Smithsonian Tropical Research Institute
2-Aug-2002

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