How Butterflies Predict the Weather

Butterflies don’t predict when it’s going to rain. (According to folklore, cows do that by sensing increased moisture in the air and lying down to preserve a patch of dry grass for grazing.) Rather than weather, the short-term changes in the atmosphere, butterflies show changes in climate, the average of weather patterns in a certain location over a long period of time.

The link between butterflies and climate was discovered by Camille Parmesan in the early 1990s, before there was any significant data on climate change. Her primary test subject was the Edith’s checkerspot, a butterfly which spends its entire life in a small habitat. It relies on one specific plant—the dwarf plantain—for food during its early development. As that plant gets hotter, the nectar dries up, making the butterfly very susceptible to environmental changes.

Parmesan thought the butterfly might be a better measure of temperature change than a thermometer, since the butterflies respond to a complex set of climate variation. She found that the butterfly shifted its range 65 miles northward and 350 feet higher in elevation during a time period with a 0.7 degree (Centigrade) rise in average temperature. This evidence that butterflies were moving to adapt to a warming climate opened up a new field of study—climate change biology. Since then, many studies have been conducted to examine how animals and plants are dealing, with varying levels of success, with the environmental changes of the last 30 years.