Study: Global warming may take aim at butterfly population (+video) - The Petri Dish

According to a new study published today in Nature Climate Change, global warming in recent years has been changing the composition and habits of butterfly communities in Massachusetts.

The populations of many butterfly species that tend to inhabit cooler climates are declining rapidly while warmer-weather species, such as the giant swallowtail and the zabulon skipperâ€"are increasing. Some of these species were entirely absent from Massachusetts as recently as the 1980s.

The authors of the study chose an interesting source for their dataâ€"the records of the Massachusetts Butterfly Club. The club exists to sponsor statewide education and conservation efforts relating to butterflies. For the last nineteen years, the club has recorded data about sightings of various species in Massachusetts. Species counts based on nearly 20,000 expeditions throughout Massachusetts provided data crucial to the study.

“It suggests the entire butterfly fauna is shifting its position northward on the eastern seaboard of North America,” Greg Breed, a Harvard University researcher and co-author of the study, told Reuters on Tuesday.

An examination of the cooler-climate species in decline reveals that the species most affected by climate change are those that overwinter as small larvae or eggs. These larvae or eggs may rely on precipitation or snow cover to survive the winter months.

Global warming and the frequent droughts associated with it may deprive these species of the climate conditions they need to survive, thus making Massachusetts an inhospitable place for them. Warmer-climate species accustomed to mild winters and limited precipitation, on the other hand, seem to find the weather conditions in recent years entirely suitable.

A number of other issues, including habitat destruction, may threaten butterfly populations in Massachusetts or elsewhere. But Mr. Breed, a postdoctoral fellow at Harvard Forest in Petersham and lead author of the study, believes that climate change is the most pressing issue at the moment.

“For most butterfly species, climate change seems to be a stronger change-agent than habitat loss. Protecting habitat remains a key management strategy, and that may help some butterfly species. However, for many others, habitat protection will not mitigate the impacts of warming,” he says.

“You have all these southern butterflies that are shifting northwards and these northern butterflies are going extinct in Massachusetts because it’s probably too warm for them,” added Breed.

Though the study is valuable in and of itself, many may find the data source to be particularly interesting. Scientific papers are seldom based on data collected by amateur societies of naturalists, yet such data can be extremely useful and valuable, as it was in this case.

Elizabeth Crone, a co-author of the paper, said: “Careful datasets from amateur naturalists play a valuable role in our understanding of species dynamics. Scientists constantly ask questions, but sometimes the data just isn’t there to provide the answers, and we can’t go back in time to collect it. This study would not have been possible without the dedication and knowledge of the data collectors on those 19,000 club trips.”