Saving San Juan Island's prairie from invasive plants

San Juan Island's prairie, where the invasive plant team works with park staff.

San Juan Island National Historical Park, in Washington's San Juan Islands, is best known for the "Pig War" standoff between the United States and Britain. Its dry coastal prairie holds something older and rarer: blue camas, a staple food for Native people, and the Island Marble butterfly, once thought extinct. Invasive plants threaten both, and a Park Service team has been working to push them back.

Thousands of years on the prairie

• Native people have lived on the island for thousands of years; their ancestors arrived around 11,000 years ago. They used fire to tend the blue camas they ate and used for other purposes, including basketry.
• Settlers of European descent arrived in the 1800s — farmers and soldiers — and turned the dry prairie over to crops and livestock. They brought nonnative plants that competed with native ones, and grazed land that suited the newcomers perfectly. Some also brought hares, which disrupted the native ecosystem further.
• The park was created in 1966 to protect this layered cultural and natural history.

Pushing back

The North Coast and Cascades Network Invasive Plant Management Team has long worked with the park's resource staff on a suite of weeds. In 2019 the team, park staff and an EarthCorps youth crew pulled invasive plants by hand and then seeded native species over 80 acres of the park's hills and fields.

The threat has not gone away. The team and park staff draw up treatment plans that serve both the site's cultural needs — like the camas — and its biological ones, like the butterfly's habitat.

Sources

Written from "Invasive Plant Control at San Juan Island National Historical Park", National Park Service North Coast and Cascades Network, a work of the United States government in the public domain.