Study: Southern butterfly species growing in Mass.

Posted Aug. 19, 2012, at 9:10 p.m.

BOSTON — Historic butterfly communities in Massachusetts are dwindling and being rapidly replaced by their southern relatives, according to a Harvard study released Sunday.

The study outlines the growth and decline of butterfly species in Massachusetts during the past two decades. During this time, the study found that warm-climate-adapted butterfly species have grown by an estimated 1,000 percent, while cold-climate-adapted species, which have long been native to the Bay State, have declined — some by up to 90 percent.

The study was conducted by Harvard Forest, an environmental research department of Harvard University, to examine the effect of climate change on butterfly communities in the state. It relies on data collected during the past two decades by the Massachusetts Butterfly Club, an amateur naturalist group that tracks butterfly populations.

Seventeen of the 21 northern butterfly species in Massachusetts, including the Atlantis Fritillary and the Acadian Hairstreak, were found to be in population decline, according to the study. These cold-climate species also were more prevalent in high-altitude regions of the state, like the Berkshire mountains and the Worcester Plateau, where scientists believe cooler microclimates exist.

Meanwhile, the study found that 12 southern butterfly species, which were rare or unseen in the state during the 1980s and 1990s, have increased tremendously, specifically in the warmest areas of the state: the Pioneer Valley and southeastern Massachusetts. The species include the Zaboulan Skipper and Giant Swallowtail.

The study does not track butterfly populations outside the state, so it does not account for whether cold-climate species have moved north.

Researchers say the butterflies most impacted by the decline are those that wait out the winter as eggs or small larvae and are more sensitive to a lack of snow cover or drought. Another reason for the growth and decline of these populations, they say, can be attributed to the fact that some of the southern species are protected by Massachusetts — because of their rare, threatened or end angered status in the state — while northern species do not.

But, Greg Breed, the study’s lead author, said that the habitat protection may not be enough to combat the perceived impact climate change is having on the species.

“For most butterfly species, climate change seems to be a stronger change-agent than habitat loss,” he said in a statement.

Elizabeth Crone, a Harvard Forest senior ecologist who worked on the report, said while she was not surprised by the results of the study, she didn’t expect data collected by a group of citizen scientists to have such clear-cut results.

Crone said she decided to lead the study based both on professional and personal curiosity. The ecologist, who moved to Massachusetts in December 2010, said she ran across the Massachusetts Butterfly Club’s data while trying to learn more about the state’s butterfly community.

She said long-term monitoring data, like that the club kept on butterfly populations in the state, is not common in the scientific community because of budget and time constraints.

“There’s been a lot of awareness about climate change effects qualitatively, but not quantitatively,” Crone said. “It’s amazing what this group of citizen scientists had done.”

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