4 Out Of 5 Butterfly Species Moving Into New Territory As Earth Heats Up

Butterflies Are Chasing a Changing Climate Across the Globe

A new global study published in Nature Ecology and Evolution confirms what many researchers suspected: butterflies around the world are changing where they live as the climate warms and landscapes are altered.

Researchers compiled records of butterfly species moving into new territory, shrinking their habitat, or shifting up or down mountains for 1,758 species across 105 countries and territories, roughly 10% of all known butterfly species on Earth. The result is the most sweeping portrait ever assembled of butterflies in motion, with climate change and severe weather identified as the most frequently reported threat linked to those movements.

An overwhelming 80% of the species studied showed signs of expanding into new areas. Meanwhile, 27% were recorded as shrinking their ranges, and 22% were shifting to different elevations. Those categories overlap because some species expanded in one region while contracting or changing elevation elsewhere. Nearly 79% of all recorded movements were tied to climate change and severe weather.

The Biggest Butterfly Range Study Ever Assembled

This research stands out not just for its size but for how it was built. Scientists searched through literature written in 15 languages and gathered input from 68 butterfly experts across 49 countries, an approach meant to close a longstanding gap: nearly half of all published research on species movement has historically come from Europe alone, leaving enormous blind spots across the tropics, where most of the world’s butterfly diversity actually lives. Relying only on English-language publications, it turns out, would have skewed the data heavily toward stories of expansion while leaving range shrinkage underrepresented. Expert assessments and non-English studies revealed far more cases of species losing ground.

Expansion and Decline, Side by Side

Among the species in the dataset, expansion records were documented for 1,427 species spanning 97 countries. Records of shrinking ranges covered 480 species across 27 countries, while elevation-related movement was documented in 381 species across 18 countries.

Range expansions were heavily documented across tropical nations, including Brazil and Benin, pushing back against earlier claims that there was little evidence of expansion in the tropics. Records of range shrinkage, though, were concentrated almost entirely in Europe and North America, places with long-running monitoring programs. That doesn’t mean tropical butterflies aren’t disappearing from parts of their habitat. It likely means no one has been watching closely enough to catch it.

Some countries stand out for how much evidence turned up. The Czech Republic had the highest documented rate of expansion, at 84%. Sweden had the highest rate of contraction, at 85%. Mexico led on elevational shifts, at 39%. Those numbers reflect how much evidence researchers found in each country, not the share of each nation’s entire butterfly population that is actually on the move.

Out of 352 species for which threat data was available, climate change and severe weather were the most frequently identified driver. Land-use pressures, including agriculture and human disturbance, were especially common in reports of shrinking ranges. In Oceania, invasive species and residential development ranked as top threats. In South America, human disturbance topped the list.

A few examples from the paper put these numbers in context. In Brazil, one species expanded its range from two states into a third in response to climate warming. In Germany, one species lost much of its bog habitat due to drainage operations. In Romania, agricultural changes caused a severe range contraction for another species. In the United States, an invasive butterfly species contributed to dramatic range losses for a native one.

Tropical Butterflies Are the Biggest Blind Spot

An important part of this research concerns what is not being recorded. Tropical regions, home to a disproportionate share of the world’s butterfly species, are dramatically underrepresented in the data. Large swaths of Central Africa, Southeast Asia, the Amazon Basin, and the island of New Guinea had little to no data in this study, even after researchers searched extensively to find it.

Tropical butterflies face particular risks. Previous research suggests that many tropical species live near their upper heat limits, occupy restricted ranges, or have limited access to cooler refuges. Where tropical studies exist, range changes are often recorded loosely as population fluctuations rather than through standardized measurements, so a species could be quietly losing ground for years before anyone notices.

Scientists behind this study are calling for a major expansion of butterfly monitoring programs in under-studied regions, especially tropical countries. They also urge conservation planners to account for the reality that species are already on the move. Protected areas, most of which were designed around fixed geographic boundaries, may be increasingly inadequate for species that are migrating across those lines. The authors point to earlier research estimating that 85% of migratory butterfly species are inadequately covered by the global protected-area network.

Butterflies have long served as a proxy for the broader health of the natural world. This study confirms that climate change is reshaping where they live, while exposing how incomplete the tools for tracking that change still are across much of the planet. Closing that gap is now as urgent as protecting the insects themselves.

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Disclaimer: This article is based on a peer-reviewed study and reflects the findings and interpretations of its authors. Reported percentages describe the study’s documented evidence and should not be read as measurements of every butterfly species worldwide.

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