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Climate change may mean vanishing act for UK butterflies

Severe droughts and increasing temperatures could wipe out certain species by 2050

Jim Asher

Climate change could mean fewer butterfly species in the UK, according to a study published in Nature Climate Change today. As extreme droughts become more frequent, local populations of butterflies in the UK will die out, researchers say; even the most optimistic climate change scenarios shows species of butterflies being wiped out.

Some of these species could go extinct by 2050

Six species, including the now-common Speckled Wood butterfly, are particularly sensitive to drought, the researchers found. If carbon emissions continue along their current path, some of these species could go extinct by 2050. And the UK will likely experience widespread extinctions by 2100.

Scientists already know that climate change won't be kind to butterflies. Some species have altered their geographic ranges in response to increased temperatures, and certain studies suggest that global warming could disrupt the timing of migration for monarch butterflies. But until recently, researchers hadn't really looked at what might happen to these insects as droughts increase and butterfly habitats become increasingly patchy and spread out. That's why this study is so important; it shows that the way in which humans alter insect habitats can exacerbate the effects of global warming.

"We could lose an astonishing fraction of biodiversity," says Jessica Hellmann, a population ecologist at the University of Notre Dame who didn't work on this study. "People should care about this information because [the study] uses butterflies as a window to how climate change will affect creatures — many of which we take for granted."

Caterpillars are very sensitive to drought

The loss of certain butterfly populations in the UK could be tragic; they're "part of our natural heritage," says Tom Oliver, a co-author of the study and an ecologist at the Natural Environment Research Council, a public funder of environmental science in the UK. And because butterflies play an important role in pollinating crops, losing them could seriously matter for humans, too. Climate change will reduce their ability to carry out this function, Oliver says — and that's more than enough reason to be "really concerned."

Caterpillars are likely to take the climate change hardest. When the plants that these caterpillars feed on dry out, these larval butterflies either die or don't grow as quickly. This means that climate change could wipe out whole insect population. And because butterfly habitats are increasingly patchy and widely spaced out due to human land use, the likelihood of other butterflies coming in and recolonizing an area has diminished. "Severe heatwaves can affect adult insects directly, but in the case of butterflies, the larval forms" — forms that include caterpillars — "are much more sensitive," Oliver says.

The study has limitations, Hellmann says. It only used data from one drought, for instance. It’s hard to tell how representative that drought could be, given that future ones may vary in length, Hellman says. The researchers also point out that they weren't able to address the possibility that butterflies might adapt to increasingly frequent droughts. They aren’t too concerned about this, however, because drought-sensitive species probably won't be able to adapt quickly enough given the speed at which climate change is taking place.

Adaptation is possible, but "unlikely."

The researchers suggest that the UK should work to restore butterfly habitats and reduce carbon emissions to prevent the loss of these insects. "Because we are locked into quite marked climate warming already, habitat restoration will be essential to provide refuges for wildlife in many places, even if emissions are reduced significantly," Oliver says.

Correction: An earlier version of this article stated that butterflies play a role in "pollinating crops, eating pests and other disease vectors, and decomposing waste," when they only play a role in pollinating crops. Other drought-sensitive species, such as bees, beetles, and earthworms participate in those activities. We regret the error.