The Issue

Plants have a strong influence on our climate, because they control the fluxes of energy, water, and carbon dioxide between the earth's surface and the atmosphere. Humans may be unwittingly changing the earth's climate by altering the structure and functiong of plant communities through many actions including deforestation, increasing the atmospheric CO2 concentrations, and raising global temperatures.

The changes in vegetation that are most likely to influence the climate include: Reduced water loss (transpiration) at high CO2 concentrations which feeds back on rainfall, changes in the height or roughness of vegetation which affect wind speed, and changes in the of the vegetation albedo (or the degree to which plants reflect light) which affect surface temperatures. Scientists will address the influence of vegetation changes on climate at a meeting sponsored by GCTE/LUCC in Barcelona, Spain, on March 14-18, 1998.

The Science

• Scientists are studying the feedbacks between vegetation and climate using computer models of terrestrial vegetation coupled with General Circulation Models, or GCMs. GCMs are the models used by climatologists to forecast of tomorrow's weather as well as to predict the earth's climate 100 years from now.

• Dr. S. Lewis (University of Wisconsin) has used such coupled models to explore the consequences of a change in the sub-arctic vegetation from tundra to boreal forest. This is a commonly predicted scenario for high latitude regions under global change. He found that forests, which are darker than tundra, create warmer temperatures in the subarctic. This allows boreal forests to survive high latitude environments and maintain the conditions of their own existence.

• The coupling of GCMs with models of the terrestrial vegetation to investigate vegetation feedbacks on climate is still in its infancy. Dr. J. Foley (University of Wisconsin, USA) will speak about the necessity to include vegetation feedbacks in GCMs to make the predictions of future climate more accurate.

Practical information: These ideas will be discussed on Day 3 (March 16) at 9:00 in the session 2 "Global change and ecosystem structure" and in the poster session following immediately.

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