Island Marble Butterfly


The Island Marble Butterfly is recognized as one of the most endangered butterflies in the world, with only about 200 known to be living in a single area on San Juan Island. These butterflies are being supported through the planting and protection of habitat areas on San Juan Island, in partnership with US Fish and Wildlife, Washington Department of Fish and Wildlife, National Parks Service, Bureau of Land Management, San Juan Preservation Trust, San Juan County Land Bank, San Juan Islands Conservation District, and several private landowners.

The Conservation District is working directly with landowners to establish and maintain habitat that is known to support Island Marble reproduction. In the coming seasons, our Youth Conservation Corps will be having a hand in restoring this beautiful butterfly by tending to the habitat plots, looking for signs of reproduction and new butterflies, and reporting to the community on findings. 


Recent Accomplishments


In 2021, San Juan County landowners added seven new protected habitat sites. The Washington Conservation Corps assisted landowners by building an additional 20,000 square feet of fenced habitat and 70 acres of open land protected from forest encroachment. Roughly twenty other habitat plots on San Juan Island are already available and helping the butterflies continue their fight to survive.

New plots will be planted with a brassica seed intended to flower bright yellow throughout spring and summer, attracting migrating butterflies across a broader range. The Brassica rapa (field mustard) is known to support the butterfly throughout their entire lifecycle. The plots range in size from 100 to 5,000 square feet and are located on both San Juan and Lopez islands. Deer fencing of the perimeter helps ensure host plants and butterfly eggs, larvae, and chrysalises do not fall victim to deer foraging or human intrusion.

Interested in learning more or would like to get involved? Please reach out to the IMB team by emailing

Washington Conservation Corps crew celebrates the completion of a protected butterfly habitat.