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Tropical Forests and Earth's Changing Atmosphere
Lewis, S.L., Lloyd, J., Sitch, S., Mitchard, E.T.A. and Laurance, W.F. 2009. Changing ecology of tropical forests: Evidence and drivers. Annual Review of Ecology, Evolution, and Systematics 40: 529-549.

Although many high-latitude regions may be benefited by warming that allows crops and forests to grow where it is currently too cold for them to do so, climate alarmists typically worry about earth's tropical regions, where they claim that just a little extra warming may spell disaster for indigenous forests.

What was done
In a thorough review of the scientific literature related to this important question, Lewis et al. evaluated tropical forest inventory data, plant physiology experiments, ecosystem flux observations, earth observations, atmospheric measurements and dynamic global vegetation models, which "taken together," in their words, "provide new opportunities to cross-validate results."

What was learned
The five researchers report that both theory and experiments suggest that over the past several decades "plant photosynthesis should have increased in response to increasing CO2 concentrations, causing increased plant growth and forest biomass." And in this regard they find that "long-term plot data collectively indicate an increase in carbon storage, as well as significant increases in tree growth, mortality, recruitment, and forest dynamism." They also say that satellite measurements "indicate increases in productivity and forest dynamism," and that five Dynamic Global Vegetation Models, incorporating plant physiology, competition, and dynamics, all predict increasing gross primary productivity, net primary productivity, and carbon storage when forced using late-twentieth century climate and atmospheric CO2 concentration data." In addition, they state that "the predicted increases in carbon storage via the differing methods are all of similar magnitude (0.2% to 0.5% per year)."

What it means
"Collectively," in the words of Lewis et al., "these results point toward a widespread shift in the ecology of tropical forests, characterized by increased tree growth and accelerating forest dynamism, with forests, on average, getting bigger (increasing biomass and carbon storage)."

These findings are just the opposite of what the world's climate alarmists are trying to make everyone believe about the supposedly deleterious consequences of the "twin evils" of rising air temperatures and CO2 concentrations. However, rather than being the bane of earth's tropical forests, 20th-century increases in air temperature and atmospheric CO2 concentration -- which have returned these meteorological parameters to more normal post-Little Ice Age values -- have actually proved to have been a great boon to the trees of the tropics.

Reviewed 3 March 2010