Imagine spotting a butterfly species in your garden you have never seen before. You might take a photo and upload it to a citizen science app, or tell a local nature group about your new encounter. It feels like a small moment of joy.

But if that butterfly has appeared in your backyard because its old home is becoming too hot, too dry or too damaged, the sighting is more worrying.

Around the world, ongoing environmental changes are prompting many butterfly species to relocate and search for new homes, a process referred to as species range shifts or species redistribution. As temperatures, rainfall and habitats change, butterflies can relocate over long distances, or even move vertically up and down mountain ranges.

Our new global study found one in ten known butterfly species has already shifted in range. So, where are they going – and why?

How do we know butterflies are on the move?

The data used in our global study was comprehensive: more than 6,180 reports of butterfly range shift from 565 studies and 68 expert assessments, which covered 1,758 species across 105 countries.

These showed 80% of the documented butterfly species had expanded their ranges latitudinally, meaning east to west, or longitudinally, meaning north to south. We found 27% had reduced their........

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