Every winter millions of monarch butterflies make their way to Mexico in search of warmer climes. The creatures travel more than 3,000 kilometers to spend the winter in the country's mountainous oyamel fir forests. Within 50 years the butterflies may find themselves with nowhere to go, however. According to a report published online this week by the Proceedings of the National Academy of Sciences, predicted climate change--particularly an increase in wet weather in the area--may make the monarch's winter home uninhabitable.

Karen Oberhauser of the University of Minnesota and A. Townsend Peterson of the University of Kansas used a technique known as ecological niche modeling to investigate what might happen to the monarchs' Mexican home. The researchers first used the program to identify climatic traits suitable for monarchs and found that it predicted the current distribution of overwintering butterflies with high accuracy. When the researchers combined these results with predictions from current climate models for those areas, they found that the monarch winter refuges are expected to experience more storms in coming years as the Mexican forests become wetter. "The conditions that monarchs need to survive the winter are not predicted to exist anywhere near the present overwintering sites," Oberhauser says. "The temperatures won't change much, but the combination of coolness and increased rain will hurt."

The scientists plan to next study the future of the butterflies' breeding areas within the U.S. Increasing temperatures could cause monarchs to move farther north, which would make their yearly trek even longer. "This study demonstrates that it is important to consider a changing climate when making conservation decisions," Oberhauser notes. "Organisms need to have habitat that supports them both now and in the future."