Why are some butterfly populations shrinking?
Credit: Antonio Machado (Some rights reserved.)
Experts say they are seeing rapid declines in the number of butterfly species – with no obvious explanation.
EarthSky spoke to Arthur Shapiro at the University of California, Davis. His study of butterfly populations in northern and central California is in its 37th year. Shapiro said their butterfly database is one of the two biggest in the world.
Arthur Shapiro: We have a series of ten localities across California from near the San Francisco Bay area to the east slope of the Sierra Nevada. And we monitor the entire butterfly fauna at each one of those stations at two-week intervals throughout the butterfly season.
Shapiro sampled butterflies at sites matched with long-term weather stations. That let his team look for correlations between climate variables and butterfly behavior. And he said, for example, that the team has seen a marked decline of the true alpine butterfly fauna, which can be found only at and above treeline. He said these alpine butterflies seemed clearly affected by climate change.
Meanwhile, at lower elevations, the pattern was less consistent, statistically, to account for the population declines. He said scientists’ best guess was that the declines were related to habitat loss.
