Greenhouse Gases Global Warming and Insects

Peter Stiling

University of South Florida

Greenhouse gases, the gases involved in determining the Earth's average temperature and climate, are accumulating at a rapid rate within the atmosphere. Such gases include carbon dioxide, methane, nitrous oxide, ozone, and chloro-fluorocarbons. By far the most important of these is carbon dioxide, CO2, whose contribution to the total greenhouse gas warming effect is at least 50%. For this reason, nearly all research pertaining to insects and greenhouse gases has focused on the response of insects to elevated levels of CO2. Global atmospheric carbon dioxide levels are increasing at an astonishing rate, mainly because of the burning of fossil fuels. The atmospheric concentration of CO2 has increased from a preindustrial level of about 270 ppm to a current level of about 365 ppm, an increase of nearly 100 ppm or 35%. According to some reports, the atmospheric concentration of CO2 will likely stabilize at four times the preindustrial levels. Most studies indicate that CO2 levels will at least double from preindustrial levels over the next five to ten decades. This increase represents one of the most large-scale and wide-reaching perturbations to the environment.

Many of the changes in insect populations likely to result from elevated CO2 will be brought about by changes in plant chemistry. The chemical changes in plants result from increases in plant carbon, decreases in nitrogen, and increases in levels of defensive compounds such as phenolics. In addition, global warming, which will result from elevated levels of greenhouse gases, may increase the reproductive capabilities of some insects and change their distributional ranges. This could change the abundance of some pest species and disease vectors. Some of the myriad effects of elevated CO2 on insects are summarized in Fig. 1.

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