Mountaintops contain many diverse clusters of butterfly species, but climate change may turn habitats into traps

A Yale-led study warns that global climate change may have a devastating effect on butterflies, turning their species-rich, mountain habitats from refuges into traps.

Think of it as the "butterfly effect"—the idea that something as small as the flapping of a butterfly's wings can eventually lead to a major event such as a hurricane—in reverse.

The new study, published in the journal Nature Ecology and Evolution, also suggests that a lack of comprehensive global data about insects may leave conservationists and policymakers ill-prepared to mitigate biodiversity loss from climate change for a wide range of insect species.

For the study, a team co-led by Yale ecologist Walter Jetz analyzed phylogenetic and geographic range data for more than 12,000 butterfly species worldwide. The team was also co-led by Stefan Pinkert, an entomologist at the University of Marburg, in Germany, and former postdoctoral associate at Yale.

They found that butterfly diversity is highly clustered in tropical and subtropical mountain systems: Two-thirds of butterfly species live primarily in the mountains, which contain 3.5 times more butterfly hotspots than lowlands.

Yet those mountain ecosystems—and surrounding areas—are quickly changing as a result of climate change. According to the study, 64% of the temperature niche space of butterflies in tropical areas will erode by 2070, with the geographically restricted temperature conditions of mountains constantly shrinking.

"The diversity, elegance, and sheer beauty of butterflies impassion people worldwide," said Jetz, professor of ecology and evolutionary biology in Yale's Faculty of Arts and Sciences and director of the Yale Center for Biodiversity and Global Change (BGC Center).

"Co-evolved with host plants, butterflies form an integral part of an ecologically functioning web of life," he added. "Unfortunately, our first global assessment of butterfly diversity and threats finds that butterflies' fascinating diversification into higher-elevation environments might now spell their demise, with potentially thousands of species committed to extinction from global warming this century."

Pinkert, a former postdoctoral researcher at the BGC Center, added, "As an entomologist, I am committed to informing the public about the distribution of insect diversity and targeted ways to protect it. Our results are insightful from an ecological point of view but unfortunately also very alarming."

Current priorities in biodiversity preservation, the researchers note, are geared towards animals and plants, rather than insects. Until now, a global assessment of the geographic coincidence of diversity, rarity, and climate change threats for an insect system did not exist.

The new assessment reveals that patterns in butterfly diversity differ strongly from those of much better studied groups such as birds, mammals, and amphibians—challenging the relevance of existing conservation priorities, the researchers said.

"This research was made possible by many years of mobilizing various global data and newly developed integrative approaches, all aimed at filling this critical information gap for at least one insect taxon," Pinkert said.

Jetz said he hoped the new study—and future research enabled by the Map of Life, a global database, directed by Jetz, that tracks the distribution of known species worldwide—will support conservation managers to include insects in their plans for biodiversity preservation.

"A reduction of carbon emissions, combined with proactive identification and preservation of key butterfly habitats and migratory corridors, will be key to ensuring that much of butterfly diversity survives to benefit future generations," Jetz said.

Co-authors of the study are Nina Farwig of the University of Marburg and Akito Kawahara of the University of Florida.