December 01, 2005

Climate change and herbivore outbreaks

This is from an open access article by J. O. Stireman et al. in the PNAS:
[M]odels of climate change have predicted greater frequency and duration of droughts in some areas, increased periods of high precipitation in others, and a widespread increase in the frequency of extreme weather events. [...] Here, we compare caterpillar–parasitoid interactions across a broad gradient of climatic variability and find that the combined data in 15 geographically dispersed databases show a decrease in levels of parasitism as climatic variability increases. [...] Given the important role of parasitoids in regulating insect herbivore populations in natural and managed systems, we predict an increase in the frequency and intensity of herbivore outbreaks through a disruption of enemy–herbivore dynamics as climates become more variable. [...]

[M]any species of parasitic wasps have been and continue to be used in biological control programs, often with appreciable success. Increases in climatic unpredictability could compromise their ability to control important crop pests, leading to increased use of pesticides.
Stireman et al. also suggest that further research on herbivore–parasitoid dynamics is "likely to provide additional incentives to slow anthropogenic contributions to global climate change." This is entirely reasonable. And following the same logic this research can provide incentives for artificially decreasing climate variability below historical levels.

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