European Butterflies Threatened by Climate Change

Anne Minard
National Geographic News

December 12, 2008

European butterflies could face dramatic extinctions should global temperatures continue to rise, a new study says.

If the colorful insects try to migrate north to cooler climes, habitat destruction—such as deforestation—and large bodies of water might stop them.

"The problem for the butterflies is that the steps they have to take [to migrate] could be rather big ones," explained Josef Settele, the study's lead author and an ecologist at the Helmholtz Centre for Environmental Research in Germany.

"They might have to bridge gaps of 30 to 40 kilometers [18 to 15 miles] in one generation, and that becomes big," he added.

If small numbers of a butterfly species do survive a northern migration, they still may not thrive. The insects may not be able to reproduce in sufficient numbers or their new habitat could degrade.

Meanwhile, even a few degrees of warming could kill most butterflies that don't migrate, the authors say.

In the past few years, scientists have predicted that plants—and the animals that depend on them—will shift to northern latitudes and higher elevations as global warming pushes them out of their native habitats.

The prevailing belief is that species that can't migrate quickly enough won't survive.

(Related: "Extinctions Could Have Domino Effect, Study Says" [September 9, 2004].)

But some researchers are cautioning against what they consider a simplistic and pessimistic viewpoint. Even Settele acknowledges that "we should not neglect the potential of nature to adapt to changes."

"Some insects are able to evolve quite rapidly—there is also some hope there," he said.

The new report appears in a recent issue of the online journal Biorisk.

Winking Out?

The new report incorporates data from thousands of volunteers participating in the Mapping European Butterflies project, the brainchild of study co-author Otakar Kudrna.

"I am most concerned about the species restricted to extremely small areas in Europe and not known to live elsewhere," he said. "Such species are extremely vulnerable and can disappear at a stroke because they have no reserves."

In the worst case scenario, the report predicted an average European temperature rise of 4.1 degrees Celsius (7.38 degrees Fahrenheit) by 2080.

In that case, over 95 percent of the present land occupied by 70 different butterfly species would become too warm for their continued survival.

The best case scenario projects a 2.4-degree-Celsius (4.32-degree-Fahrenheit) temperature rise, meaning that 50 percent of the land occupied by 147 different butterfly species would become too warm.

Bigger Picture

Camille Parmesan, an ecologist at the University of Texas at Austin, has monitored butterflies in both Europe and the United States that have already shifted their ranges in response to climate change.

She has found early data showing that the more mobile and hardier species—like painted ladies—are able to migrate with climate shifts, but the more fragile and sedentary types have not budged.

It's too soon to say whether the species staying behind are stressed, she said.

Birds are also showing temperature-related shifts.

Vincent Devictor of the National Museum of Natural History in Paris found that birds have shifted their ranges northward in response to climate change by 56 miles (91 kilometers)—but temperature has shifted by 170 miles (273 kilometers).

"Change in community composition was thus insufficient to keep up with temperature increase: Birds are lagging approximately 182 km [113 miles] behind climate warming," Devictor and colleagues wrote in the August issue of the journal Proceedings of the Royal Society B.

Even when animals can move to beat the heat, the plants they rely on for food and shelter might not be able to accommodate them in their new locales.

Pinyon pine, for example, is a dominant tree species of desert southwest uplands in the United States.

Kenneth Cole, a paleontologist at Northern Arizona University in Flagstaff, has studied fossils to document pinyon pine migrations of no more than 148 feet (45 meters) per year during past warming episodes in Earth's history.

"That's not going to cut it in terms of keeping up with global warming for pinyon," said Niel Cobb, an ecologist at NAU and one of Cole's colleagues.

Mixed Bag

University of Texas's Parmesan said she worries most about isolated mountaintop butterflies that she hasn't yet studied.

"You don't need a climate projection to know those aren't going to do well with even a few degrees of warming," she said.

But that's where Mark Schmidt, an ecologist at the University of California at Davis, sees the most hope.

Schmidt perceives a flaw in models that assume species restricted to a certain area will wink out because of climate change.

Some isolated, mountaintop species have "experienced glacial and interglacial periods on that same spot," he said.

"These papers are right in sounding the alarm," he said, "but these models have to be considered as hypotheses rather than predictions."