Managing Grasslands with Fire
Fire is a powerful force for change in the environment, seemingly destroying all that lies before it. Although a blackened landscape provokes strong emotions, fire is a natural part of the ecology of prairies and other wildlands and the recovering areas support a rich diversity of wildlife. Because of the benefits of fire, controlled burns are frequently used by land managers to remove invasive weeds and maintain natural plant communities. How these burns affect butterflies and other insects is less understood.

Over the past six years, Xerces scientists have been studying the impacts of a controlled burn on a butterfly that lives in meadows in the coastal mountains of northern California. The mardon skipper (Polites mardon) is a rare butterfly found only in the Pacific Northwest of the USA. It was once more widespread and abundant but 150 years of human settlement, livestock grazing, fire suppression, and invasion of grassland habitat by native and nonnative vegetation has led to the loss of both suitable habitat and the butterflies themselves.

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 late fall 2008, the U.S. Forest Service burned approximately one third of the core habitat occupied by the mardon skipper at that site. Subsequent surveys undertaken by our scientists found significantly fewer butterflies in the burned areas compared to unburned areas, something that was consistent for the duration of the study. While the results do show a steady improvement in areas that were burned, the mardon skipper population was not back to pre-fire levels five years after the burn. The results of this study were published this month.

Fire can be a beneficial management tool for maintaining healthy habitats. However, it must be used with caution to avoid eliminating the very species that it is meant to benefit. The Coon Mountain study highlights the need to leave substantial habitat for mardon skippers when using fire, and allow enough time for the butterflies to recover before burning again. Unburned areas are essential to ensure the remaining butterfly population is large enough to survive the (ideally short-term) decrease in habitat quality and quantity, and serve as a source to repopulate the affected areas.

For More Information:The study of fire impacts on mardon skippers on Coon Mountain was made possible thanks to funding from the U.S. Forest Service, U.S. Fish and Wildlife Service, the Oregon Zoo, and Xerces Society members.

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Photo Credit: Mardon skipper by Rich Hatfield/The Xerces Society.

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