Warmer autumns could spell bad news for butterflies, suggests study

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New research finds that longer and warmer autumns make it less likely that green-veined white butterflies will survive winter to emerge in spring. The findings are published in the British Ecological Society journal, Functional Ecology.

warmer and longer autumn conditions lost more weight and used more energy than those exposed to milder conditions. Although the butterflies didn't die immediately under the more elevated conditions, the researchers found that those that experienced them were less likely to survive to adulthood the following spring.

Dr. Matthew Nielsen at the University of Oulu, who conducted the research at Stockholm University, said: "Climate change is making autumns warmer and last longer, and it was this specific combination of conditions that had the greatest impact on the butterflies in our study. We show that stressful conditions experienced at one time of year can have lasting negative consequences at other times of year, linking changes in one season to consequences in others."

Animals that enter a dormant stage through the winter are especially vulnerable to warming temperatures because this raises their metabolic rate, causing them to run out of energy faster. "Even though dormant animals use less energy than active animals, they use more when it's warmer, and they can't eat to replace that lost energy." Explained Dr. Nielsen. "It is already established that warmer winters are actually worse for dormant animals than colder ones, and our findings show that warmer autumns are potentially even more dangerous."

In Sweden, where the study was conducted, the spring generation of green-veined white butterfly is usually the smallest generation because of the stress of winter dormancy. The authors warn that the increased mortality they observed after warmer and longer autumn conditions could therefore have a severe impact on the abundance of this species at a critical time of year.