A giant swallowtail, once found only in subtropical and warm temporate regions, is now becoming a common sight in Massachusetts.

Up north that is. Climate change is driving butterflies that were once only seen in Southern US states farther to the north. A study in Massachusetts has found an increase in the population of butterfly species that were once only found in the southern US. They also found that populations of species that were once abundant in Northern states like Massachusetts are now in decline especially in warmer low altitude regions. From Nature:

Of the 21 northern species, 17 were declining, one was increasing and three did not show significant trends through time…

Further along in the article we get this bit of information:

[W]e identified species that had recently expanded their ranges by comparing our species list with the Massachusetts Butterfly Atlas (MBA; ref. 17), compiled between 1986 and 1990. Of the 100 estimated population trajectories, 14 were from species that were very rare or not reported in the atlas (four or fewer reports). Of these, 12 have southerly ranges, one has a northerly range and one is near its range core. The species with a northerly range was the only one in decline, whereas the 12 with southerly ranges were all increasing. Many of these growing populations are new to the state and represent invasions from the south (Fig. 1). Declining northern species are being replaced by warm temperate and subtropical species such as the giant swallowtail (Papilio cresphontes) and zabulon skipper (Poanes zabulon)¹⁸. Permutation tests indicate that this pattern of increase by historically (1980s) rare southern species is highly significant (p = 0.0003).

The article is very interesting. Head over to Nature to read more.