Butterflies globally are on the move across continents and new territories, shifting their ranges to adapt to the warming world and survive extreme weather events, according to a new study.
The paper, published in the journal Nature Ecology & Evolution, assessed records for 1,758 butterfly species across 105 countries, representing nearly 10 per cent of the known diversity of these insects. The findings painted a complex picture of “winners” expanding into new territories and “losers” being pushed toward local extinction.
The study noted that 80 per cent of the species experienced range expansions and nearly 79 per cent displayed range shifts to cooler regions associated with climate change and severe weather events.
“‘Climate change and severe weather’ was reportedly associated with the horizontal range expansions of 163 species, the horizontal range contractions of 131 species and the elevational range shifts of 61 species,” the assessment said.
According to the authors, a significant proportion of species — amounting to almost 27 per cent — showed contraction in their ranges while 22 per cent shifted along elevational gradients.
The range shifting has been observed to be highest in Europe, making it a hotspot with countries such as Sweden, Finland, Spain, Luxembourg, and the Czech Republic reporting range shifts for over 50 per cent of their local butterfly fauna. Sweden, in particular, stands out as a focal point for both horizontal expansions with 61 per cent and severe contractions at 85 per cent.
“Horizontal expansions were reported across all continents, with particularly high numbers of records in the tropics such as Brazil and Benin, challenging the most recent synthesis claiming little evidence for range expansions in the tropics. In contrast, horizontal range contraction reports were far less common outside of Europe and North America, with the highest density of reports being concentrated in temperate countries (for example, Belgium, UK and Sweden),” the study said.
The UK had the highest percentages of horizontal range contraction at 63 per cent and elevational range shifts of 18 per cent, respectively.
The paper added that the elevational range shifts were detected across tropical, temperate and boreal regions, but almost exclusively from the Northern Hemisphere.
Substantially fewer records of elevational range shifts were noted from the tropics despite steeper adiabatic temperature declining faster with elevation in these regions and despite lapse rates therein, which would theoretically facilitate faster upslope redistributions in response to global warming, the authors noted.
Approximately two-thirds of all butterfly species are primarily mountain-dwellers and have become crucial landscape for elevations shifts. However, mountain climates are rapidly degrading in the face of climate change, the study said.
“Elevational range shifts are particularly important as butterfly species richness, endemism and phylogenetic diversity are highly clustered in mountainous regions worldwide,” it added.
Mexico emerged as a key hotspot in this category, with 39 per cent of its documented shifting species moving vertically.
With regards to India, the study said that one species, the Tawny Coster (Acraea terpsicore) — a butterfly native to the Indian subcontinent — has rapidly expanded its range across South Asia into Australia at a speed of 135 km per year.
This is significantly high as for example, between 1988 and 2011, the Painted Lady (Vanessa cardui) shifted upslope in Mexico at a rate of 83 metres/year, while the Queen (Danaus gilippus) shifted downslope at 32 metres/year.
While the Tawny Coster’s expansion is measured in kilometres, the elevational shifts are measured in metres. This difference underscores the varying dynamics of redistribution, where species like the Tawny Coster (native to the Indian subcontinent) exhibit high mobility across continents, whereas others make finer-scale adjustments to track suitable temperatures within mountain ranges, the authors noted.
The researchers note that this expansion is cited as a prime example of how some species utilise “niche conservatism” to track suitable climates across vast distances.
The scientists enumerated nine threats, including climate change and extreme weather events, as the dominating factors pushing the species into range shifting mode.
The other threats included ‘human intrusions and disturbance’ and ‘agriculture and aquaculture’ as the most frequently reported associated with horizontal range contractions consisting of 143 species. While ‘climate change and severe weather’ was the most frequently reported threat linked to horizontal range expansions and elevational range shifts, recording 163 and 61 species respectively, the study said.
‘Energy production and mining’ was categories as the least reported.
Other threats included ‘residential and commercial development’, as well as ‘invasive and other problematic species, genes and diseases’, and were most prevalent in Oceania, while ‘human intrusions and disturbance’ was dominant for South America.
Researchers warned that biodiversity-rich areas like the Amazon Basin, Southeast Asia, and Central Africa remain dangerously under-represented in current monitoring, despite being home to the majority of global diversity.
The authors observed that butterflies tend to expand more than they contract their ranges likely due to their phenotypic plasticity, which allows local populations to survive in areas near the range margin by adopting opportunistic or behavioural strategies.
The scientists concluded that protecting micro-refugia and limiting global warming are key to preventing biodiversity collapse of the species and suggested a shift from static conservation to adaptive planning.
“Climate change mitigation remains central to minimising the climatic debt— the lag between shifting isotherms and population responses. Even small temperature increases may exceed physiological limits, alter seasonal phenology or disrupt biotic interactions with host plants and mutualists. For example, with rising temperatures, Scandinavian butterflies have expanded northwards, whereas alpine species are being squeezed towards mountain tops,” the study said.
It added that across Europe and South America, butterflies retreat to shaded or forested areas on hot days, highlighting the role of microrefugia. Because the goal of holding global temperature increase below 2 °C, while pursuing efforts to limit warming to 1.5 °C, as established in the Paris Agreement, is becoming increasingly unachievable, conservation must pair mitigation with adaptation — such as protecting microrefugia, buffering habitat edges and improving landscape connectivity — to build resilience.