Although discussions of climate change often focus on the trouble it will cause for humans, it is vital to remember that continued warming may have just as drastic an effect on plant and animal populations. A new study from Harvard University, published in Nature Climate Change, highlights another way that climate change is altering the world as we know it: as the climate warms, butterfly species are moving farther north, away from their traditional habitats.
In order to have a complete set of data to work with, the Harvard researchers teamed up with the Massachusetts Butterfly Club, an amateur naturalist group. The group provided the scientists with 19 years’ worth of meticulous butterfly species counts, gathered on almost 20,000 amateur expeditions.
The researchers discovered that many warm-climate butterfly species have had the sharpest increases in abundance. For instance, the giant swallowtail (pictured above) and the zabulon skipper have been historically considered to be “southern butterflies;” they were rare in Massachusetts in the 1980s, but climate change has increasingly driven them north.
Meanwhile, over three-quarters of northern butterfly species are rapidly declining in Massachusetts, especially those species whose eggs or larvae must live through the winter. If a season brings droughts or insufficient snow cover, these species could face extinction crises.
The study’s lead author, postdoctoral fellow Greg Breed, discusses how the implications of the study alter the ways we must approach saving endangered species:
“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,” says Breed. He points to the frosted elfin, a species that receives formal habitat protection from the state. This southerly distributed butterfly is now one of the most rapidly increasing species in Massachusetts, with an estimated 1000% increase since 1992. Some of this increase may be due to habitat protections, Breed allows. But over the same period, atlantis and aphrodite fritillaries, historically common summer butterflies in Massachusetts, have declined by nearly 90%—yet these northerly species remain unprotected.
Only time will tell if habitat and species protection will be sufficient to help these butterfly species survive a changing world, or if slowing global climate change is the only way to sustain them.