Butterflies that struggle to regulate their body temperature are moving to higher elevations faster than other species, according to a new study. The findings suggest that climate change may be reshaping where wildlife lives, with some species shifting their ranges rather than adapting to warmer conditions.In a new study in the peer-reviewed journal Communications Biology, available through Nature, carried out by researcher Esme Ashe-Jepson from the University of Würzburg, it was found that butterfly species that had low thermoregulatory ability were undergoing the most pronounced upward range shifts along an elevation gradient in central Europe.This study adds to evidence that climate change is altering biodiversity and may force some species to relocate.Why butterfly thermoregulation mattersDifferent from mammals and birds, butterflies cannot generate their own body heat. They rely on external factors like sunlight, shade, and air temperatures to ensure a proper body temperature, which helps them move, eat, and mate.As revealed by the Communications Biology study, the ability to regulate body temperature varied among the species studied. Species that were least effective at regulating body temperature were the ones that moved to higher elevations over time, suggesting that moving to cooler places may help them cope with warming. Moreover, there was no difference in thermal characteristics among populations of the same species at different elevations. This suggests that body-temperature regulation may be relatively stable rather than easily adjustable.Body size and color affected heat toleranceIn this study, butterflies were examined across an elevational gradient in central Europe for thermal properties and traits such as wing size, coloration, wing condition, and sex. Larger butterflies were better able to avoid excessively high body temperatures at lower elevations. However, dark-colored butterflies, even when they showed some improvement in thermoregulation at low elevations, still reached higher body temperatures than light-colored individuals.Such results suggest that smaller and darker butterflies may be particularly exposed to excessive heat conditions that are becoming more frequent due to global warming. The study also reflected a broader ecological pattern. In higher elevations, smaller and darker butterflies can be found, while larger and light-colored species inhabit lower elevations.
Image of a butterfly. Image Credit: Wikimedia Commons
Climate change could be redistributing the species rather than adapting themOne interpretation of the findings is that the butterflies may be responding to climate change through migration rather than rapid evolution of thermal adaptation. Butterflies that had poor thermoregulation ability, along with those that possessed large wings, exhibited the most elevational shift. According to the author, this indicates redistribution of the species rather than adaptation within the population.Scientists have long known that mountain habitats are especially vulnerable to climate change because species moving uphill eventually reach an altitude beyond which they cannot go. Such trends have been found before among mountain butterfly communities. In fact, according to the Nature Climate Change study, many European mountain butterflies have already begun their upward shift due to warming.A broader alarm for biodiversityThese observations are in line with the Intergovernmental Panel on Climate Change, which says climate change is already driving changes in the geographic distribution of many species worldwide. While many species move northwards or upwards as a result of temperature increases, not all of them are able to keep up.The IPCC Sixth Assessment Report says the process is likely to accelerate with further warming, increasing the risk of local extinction, especially in mountainous areas. The findings also support broader concerns raised by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), which identifies climate change as one of the major drivers of biodiversity loss worldwide.The report synthesizes the work of 145 governments and concludes that, out of about 100,000 assessed species, roughly 1 million are threatened with extinction, many within decades. It identifies land and sea-use change, direct exploitation, climate change, pollution, and invasive alien species as the main drivers of biodiversity loss, and warns that nature is declining globally at a rate unprecedented in human history.Implications of the findingsAlthough butterflies are often seen as colorful, they are also useful indicators of environmental change. Their temperature-sensitive physiology and short life cycles make them useful indicators of environmental change. The findings suggest that some butterfly species may be nearing the upper limit of their heat tolerance. Rather than adapting to the growing levels of heat, many of them are shifting towards cooler regions by going upwards.As temperatures continue to rise because of climate change, scientists say studying species with the lowest heat tolerance can help conservationists identify those at higher risk. However, for mountain fauna, moving uphill is not a permanent solution because there may be nowhere else to go once the peak is reached.