Climate change affects the flight period of butterflies in Massachusetts

"Butterflies are very responsive to temperature in a way comparable to flowering time, leafing out time, and bee flight times," says Richard Primack, professor of biology and study co-author. "However, bird arrival times in the spring are much less responsive to temperature." As a result, climate change could have negative implications for bird populations in the Northeast, which rely on butterflies and other insects as a food source. The team, which includes Caroline Polgar (Boston University), Sharon Stichter (Massachusetts Butterfly Club), Ernest Williams (Hamilton College), and Colleen Hitchcock (Boston College) will publish its findings in the February 12 online edition of the journal Biological Conservation.

While the effect of climate change on plant and bird life cycles in eastern North America has been well examined, studies of the effects of climate change on insects are rare, so these findings represent an important contribution. This new study investigated whether the responses to climate warming in Massachusetts of ten short-lived butterfly species known as elfins and hairstreaks are similar to responses seen in plants, birds and bees. Another unique feature of this study is its use of data from museum collections as well as data gathered by the Massachusetts Butterfly Club, a group of dedicated citizen scientists who love butterflies. Use of this data gave the researchers an opportunity to compare butterfly flight periods dating back to the late 1800s.

The researchers obtained over 5000 records of butterflies in flight using museum collections (1893-1985) and citizen science data (1986-2009), then analyzed the data using statistical models to determine how butterfly flight times are affected by temperature, rainfall, geographic location, and year.

The researchers found that the start of the butterfly flight period advances on average by two days for each degree Fahrenheit increase in temperature. The response of these butterfly species to temperature is similar to plant flowering times and bee flight times and is significantly greater than bird arrival times, which increases the likelihood of ecological mismatches with migratory birds arriving after the first spring flush of their insect food.

The researchers also found that observations by citizen science groups such as the Massachusetts Butterfly Club were an effective and largely untapped source of information that could be used to investigate the potential impacts of climate change on butterflies. Such data provides an opportunity to inform conservation policies on these species and associated habitat. While data from museums was helpful, it was less abundant and therefore less useful than the citizen science dataset.