Analyzing 19 years of data from field trips by the amateur naturalist group the Massachusetts Butterfly Club, researchers at Harvard University said they've filled a crucial gap in the scientific record.
More than three-quarters of northerly species, those with a range centered north of Boston are now declining in Massachusetts, many of them rapidly, a Harvard release reported.
Meanwhile subtropical and warm-climate species such as the giant swallowtail and zabulon skipper -- rare or absent in Massachusetts as recently as the late 1980s -- have shown sharp increases, researchers said.
"For most butterfly species, climate change seems to be a stronger change-agent than habitat loss," lead study author Greg Breed said.
"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."
Study co-author Elizabeth Crone said information from amateur groups such as the butterfly club is vital in such studies.
"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.
"Careful datasets from amateur naturalists play a valuable role in our understanding of species dynamics," she said.