Studies warn that butterflies are shifting, declining, and remain unmonitored in tropical countries

Three scientific papers published this year converge to suggest that butterflies are shifting from where they live, dwindling in number at many places where they do exist, and remain almost entirely unmonitored across the tropical countries that hold most of the world's butterfly diversity, including India.

The three studies, Extensive Climate-Induced Range Shifts in Butterflies Across the Globe; A Framework for the Strategic Conservation of Tropical Insects; and Addressing Gaps in Butterfly Population Monitoring to Catalyze Global Insect Conservation, were published in Nature Ecology & Evolution; Bioscience; and Conservation Letters, respectively, and represent one of the largest coordinated efforts to understand how butterflies are responding to habitat loss and climate change.

On the move

The Nature Ecology & Evolution study, led by Shawan Chowdhury and involving contributions from Krushnamegh Kunte of the National Centre for Biological Sciences (NCBS), Bengaluru, analysed documented range-shift records of 1,758 butterfly species across 105 countries -- slightly less than 10% of all known butterfly species -- by combining published literature in 15 languages with assessments from 68 butterfly experts worldwide.

Most species studied (80%) had expanded their ranges, and the large majority of these shifts (79%) were linked to climate change and extreme weather. But more than a quarter of species had also lost part of their range, and nearly a quarter showed shifts along elevational gradients -- species moving upslope or downslope as temperatures changed.

The study found that horizontal range expansions dominated in tropical countries, while range contractions and elevational shifts were reported almost exclusively from Europe and North America, not because tropical butterflies are more resilient, the authors noted, but because almost no one is watching them closely enough to detect contractions or elevational movement in the first place. Data gaps remain severe in many of the tropical countries, making informed decisions about conservation action considerably more difficult.

Data gaps

The study published in Conservation Letters, which was led by David Roy and co-authored by Mr. Kunte along with other researchers from the Indian Foundation for Butterflies Trust and the Bengaluru Butterfly Club, attempted to build a butterfly equivalent of the Living Planet Index, the metric long used to track vertebrate population trends worldwide.

Drawing on over 45,000 population time series covering 1,055 species from 3,636 locations in 37 countries, the team calculated an average 24% decline in monitored butterfly populations since 1995, with significant declines in North America and some declines in Europe.

The catch, again, is that the vast majority of the underlying data comes from Europe and North America, where standardised, volunteer-driven monitoring schemes have run for decades. The rest of the world, including the tropics, where most butterfly diversity actually occurs, remains so undersampled that the trend estimate for those regions carries considerable uncertainty.

According to the authors, without robust monitoring, it will be difficult to assess the effectiveness of management actions implemented to protect pollinators and meet global biodiversity conservation targets, to many of which India is a signatory.

Scientific, citizen-led approach needed

The Indian Butterfly Monitoring Scheme (iBMS), a nationwide citizen-science initiative, was launched in 2021 to systematically monitor butterfly populations across India. Both the Conservation Letters and BioScience papers single out iBMS as one of a handful of monitoring programmes now taking root in tropical, historically data-deficient countries.

"Butterfly monitoring is not a luxury for wealthy countries with time to spare; it is the kind of low-cost, high-return science that a developing country needs the most, because it lets us target conservation and development investments where they will actually work... If we get this right, India will not just be catching up to global butterfly science -- we will be showing the rest of the tropical world how it is done," said Mr. Kunte, who is the founder and coordinator of iBMS and a co-author of all three research papers.

The research papers advocate expanding standardised butterfly monitoring in the tropics, integrating citizen science with structured long-term data collection, and building that evidence directly into conservation planning and protected-area design rather than treating insect biodiversity as an afterthought.