Some plants and animals living in the coolest edges of their habitat are thought to benefit from a bit of extra heat courtesy of climate change, at least in the short term. That was widely assumed to be the case for butterflies and moths in cool, drizzly Great Britain. Maybe they’re growing in numbers and expanding their ranges northward. But a new analysis of 155 of these fluttery species revealed that for many, that’s simply not the case.
Species vary in their sensitivity to climate, and despite being faced with the same changes, they respond to different components, such as rainfall or seasonal temperatures. As a result, they end up being exposed differently. The findings are published in Science Advances this week.
In the last 40 years, some species of moths and butterflies have spread while others have declined. Exactly what drives the variation in responses to climate change among species is poorly understood. To investigate, a team led by University of York’s Georgina Palmer and Chris Thomas studied three common responses – changes in abundance, distribution size, and location of the northern range margin – of 24 butterflies and 131 moths in Great Britain. First, they built species-specific climate models to determine sensitivity and exposure, and then they quantified the responses.
Half of the species they studied responded positively to warm conditions during the summertime, while the other half responded negatively. And because each species is sensitive to different aspects of the climate, they might be ostensibly experiencing the same changes, but they end up being exposed to different levels. "How much their specific 'view' of the climate has changed for them over the past few decades also varies," Palmer tells IFLScience. About 60 percent of the variation in abundance can be explained by these species-specific differences; it’s 53 percent for variation in distribution changes.
Climate improved the most for the treble brown spot moth and the speckled wood butterfly: They experienced the greatest increases in distribution size and abundance. Meanwhile, the grizzled skipper butterfly (pictured above), the September thorn moth, and the mouse moth have experienced deteriorating climates, which resulted in declining abundance and distribution size.
"Some like it hot, some like it cold. Some like it hot in winter but not in summer. Some like it wet in spring, others dry in the autumn,” Thomas says in a statement. "It turns out that these 155 different species of butterflies and moth have almost 155 different 'opinions' on how much the climate has changed, and whether it has got better or worse.”