Global warming's effects extend to world's smallest butterfly

The latest issue of Conservation Biology examines the viability of the Sinai baton blue and the results of human population pressures. The study predicts that in the absence of global warming, grazing, and plant collection (three activities directly linked to humans) the world's smallest butterfly would persist for at least 200 years. The population could withstand small increases in grazing intensity that would decrease their climate, but not increases in temperature. As the level of global warming raises its impact, extinction rapidly accelerates. This implies "…that there may be an annual average temperature, specific to each endangered species, above which extinction becomes much more likely," authors Martin Hoyle and Mike James state. There is no such threshold of grazing pressure.

The authors mapped the entire global range of this butterfly and obtained data on the intensity of livestock grazing. The Sinai baton blue is one of only two endemic animals in St. Katherine's Protectorate, one of Egypt's most recently designated protected areas. Based on the authors' model, the effect of global warming on the chance of extinction does not depend on the future level of habitat destruction due to this grazing; the growing number of families that live on the protectorate keep a small herd of goats and sheep that graze on the plants the butterflies thrive on. Global warming is the deadly culprit. "If the areas of habitat patches individually fall below certain prescribed levels, the butterfly is likely to go extinct,"the authors conclude.

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