A newly published study from Western Washington University has documented a striking ecological loss: 93% of the persistent, old-growth grasslands that once covered the San Juan Islands have disappeared since the 1890s. The research, co-authored by WWU faculty and a recent graduate, used historical mapping data and multispectral aerial imagery to trace land cover changes across the islands over more than 130 years.
The study, titled "Historical Loss of Native Old-Growth Grasslands on the San Juan Islands, Washington," was published in the journal Ecologies in late June. It represents one of the most comprehensive spatial analyses of grassland loss in the Pacific Northwest island chain and quantifies a change that conservation biologists and land managers have long suspected but had not formally measured at this scale.
The research was conducted by Kailey Schillinger-Brokaw, who completed her master's degree in environmental studies with a focus on geography and geographic information science at Western Washington University in 2023, and Aquila Flower, professor of geography in the Environmental Studies Department and director of Western's Spatial Institute. Their methodology combined historical maps, black-and-white aerial photographs from the 1930s, and contemporary multiband aerial imagery processed through Geographic Information Systems, or GIS, to create spatial datasets tracking land cover from the 1890s through the present day.
The findings are striking in their precision. The study found not just a general decline in grasslands, but a net 77% decrease in all non-agricultural grasslands and a 93% loss specifically in the persistent, old-growth grassland category, which refers to grasslands that existed continuously over the long historical record. These are not just any open areas, but ancient, ecologically complex systems that took centuries to develop and provide habitat for rare and endemic species found nowhere else in the world.
Among the species that depend on these grasslands is the island marble butterfly, one of the most endangered insects in North America. The island marble was thought to be extinct for decades before a small population was rediscovered on San Juan Island in 1998. Its survival is directly tied to the availability of native grassland plants. The loss documented in the study puts the ongoing recovery of the island marble butterfly and other endemic species in stark numerical context.
The researchers also highlight the cultural dimension of the grasslands. Coast Salish peoples, whose traditional territories include the San Juan Islands, maintained many of the islands' open grassland systems through cultural burning practices over thousands of years. The dramatic decline in grassland cover since the 19th century reflects both the cessation of those practices after European colonization and the conversion of land to agricultural use, development, and invasive species encroachment.
Schillinger-Brokaw, now a GIS specialist for the New York Natural Heritage Program in Albany, spoke to the concept of a "shifting baseline," a well-documented phenomenon in ecology where each generation recalibrates its sense of what constitutes a healthy or normal ecosystem based on what it grew up seeing. "My hope is that this study can help prevent that from happening to the grasslands," she said, noting that quantifying historical loss is one of the most effective tools for anchoring conservation goals in a realistic baseline.
For Whatcom County residents, the San Juan Islands sit just offshore and the ecological health of the archipelago is closely tied to the broader Salish Sea ecosystem. The study adds to a growing body of research from Western Washington University documenting environmental changes in northwest Washington. The university's College of the Environment and the Spatial Institute have become regional leaders in applied environmental research, and this study is a strong example of graduate-level work with direct conservation relevance.
Conservation organizations and land trusts working in the San Juan Islands, including the San Juan Preservation Trust and the San Juan County Land Bank, have been engaged in grassland restoration efforts for years. The new data from WWU provides a stronger quantitative foundation for restoration prioritization and grant-making. Readers interested in the full study can access it through the journal Ecologies, published by MDPI, which operates on an open-access model.
