Study looks at how controlled burning affects rare butterfly

The Xerces Society has released a study that shows that caution should be used when applying prescribed fire in rare butterfly habitat.

The mardon skipper (Polites mardon) is a rare butterfly found only in the Pacific Northwest of the United States of America. Historically, mardon skippers are thought to have been more widespread and abundant than they currently are but 150 years of human settlement, livestock grazing, fire suppression, and invasion of grassland habitat by native and nonnative vegetation have led to the loss of habitat and butterflies.

Staff from the U.S. Forest Service, U.S. Fish and Wildlife Service, and the Xerces Society designed a study to determine the effects of fire on mardon skippers on Coon Mountain in northern California. In late fall 2008 the U.S. Forest Service conducted a burn that impacted approximately one third of the core habitat occupied by the mardon skipper at that site.

Subsequent surveys undertaken by Xerces Society scientists found significantly fewer butterflies in the burned areas of Coon Mountain meadows compared to unburned areas. In all years of the study there were more mardon skipper butterflies in unburned zones than in burned zones. While the results do show a steady improvement in areas that were burned, full recovery had still not taken place five years after the burn event. This highlights the need to leave substantial habitat when using fire as a management tool for mardon skippers, and likely other imperiled butterflies. Untreated habitat is essential to ensure the remaining butterfly population is large enough to survive a prolonged (although ideally short-term) decrease in habitat quality and quantity, and can serve as a source to repopulate the affected areas.

Fire can be a beneficial management tool to maintain healthy ecosystems. However, this study shows the importance of using fire and other management tools with caution. Careful consideration of the life histories of the resident flora and fauna will help to avoid eliminating the very species that such management is targeting.

To read the report, click here.

Funding from the U.S. Forest Service, U.S. Fish and Wildlife Service, the Oregon Zoo, and Xerces Society members made this study possible.