The study, led by Monash University in Melbourne, Australia, found that 80 percent of species expanded into new areas. However, 27 percent saw their ranges shrink, and 22 percent are shifting elevations in search of suitable habitat.

“We are clearly observing that species are colonizing higher elevations and that additional species are spreading, both in South Tyrol and more generally across the rapidly warming Alpine region,” explains biologist Elia Guariento who has been surveying butterflies in Austria and South Tyrol for nearly a decade and has conducted systematic monitoring in South Tyrol since 2019 as part of the region’s Biodiversity Monitoring program. “In recent years, we’ve found several species – such as the Apollo butterfly, at elevations where we didn’t expect them. The study confirms that this is also a clear global pattern.”

The data primarily documents the expansion of ranges because this aspect of change is the easiest to detect, Guariento explains: “If a species appears in an area where it has never been observed before, this is usually recorded quickly. When species decline because they can no longer find the right conditions, or even disappear, this often takes some time to be ascertained. To track such developments accurately, we need long-term monitoring programs, of which there are still far too few.”

Many regions with particularly high biodiversity, such as the tropics, are still virtually blind spots in research. Where data availability is better, a picture of profound change emerges: In 32 countries, changes in distribution were documented for a quarter of their known butterfly species; in ten countries, the figure was even higher than half.

The study – the largest of its kind to date – also analyzed the causes of these changes. The expansion of ranges and migration to higher elevations are primarily linked to global warming and extreme weather events. When ranges shrink, however, land-use changes such as the intensification of agriculture or the loss of wetlands often play a significant role.

Butterflies are among the most extensively studied groups of insects. Because their habitat requirements are well understood, they serve as excellent bioindicators of ecological changes. “They are an early warning system,” says Guariento. “The study’s findings are therefore truly alarming. If butterfly ranges are changing so drastically, we can assume that the same applies to other insect groups – we just don’t have the data to prove it yet.”

The study is freely available at: https://www.nature.com/articles/s41559-026-03117-y