Butterflies facing climate challenge

Mild winters are causing falls in butterfly numbers in the United States, according to a new study by Jessica Hellmann, associate professor of biological sciences at the University of Notre Dame, and researchers from Western University.

The study focussed on the Propertius Duskywing butterfly, which has a high metabolic rate, burning more fat during milder winters. "The energy reserves the caterpillars collect in the summer need to provide enough energy for both overwintering and metamorphosing into a butterfly in the spring," says Caroline William, one of the authors the study.

The caterpillars however, do not always respond to the temperature in a simple fashion. The study showed those in regions of high winter temperature variations were more prepared for milder winters and were able to cope, whilst those in areas with consistently cold winters were less able to adapt during a milder winter.

It is a cause for concern as some regions of the world are set to experience much milder winters in future. "We still have lot to learn about how organisms will respond to climate change," Hellmann said. "Our study shows significant biological effects of climate change, but it also shows that organisms can partially adjust their physiology to compensate. We now need to discover if other species adjust in similar ways to our example species."

The research is likely to now look at other species and whether the issues associated with high metabolism will affect them as well. Milder winters might be seen from a human perspective as one of the less damaging impacts of climate change, but the unbalancing of the climate and biosphere is perhaps more insidious than people first realise.