Indigenous communities have been creating clam gardens for more than 4000 years in the Pacific Northwest, but the practice had all but disappeared until it was revived earlier this month by members of the Swinomish Indian Tribal Community in northern Puget Sound. 

Project manager and marine ecologist with the Swinomish Tribe, Courtney Greiner, describes the effort as a biocultural restoration project, which restores both the ecosystem and human cultural relationships. “The [tribal] community is concerned, not only about the future loss of traditional harvest sites from sea level rise and impacts to the health of shellfish due to the changing water conditions, she says, but the subsequent loss in intergenerational knowledge sharing, food security, and identity.”

The Swinomish reservation is located in Northern Washington on Fidalgo Island, and has over 3000 acres of tidelands. To choose an optimal site, the project team completed a geospatial analysis, informed by a technical advisory board consisting of Coast Salish knowledge holders, Swinomish Tribal members, and scientists. Fifteen potential sites were identified and ranked based on physical and socio-cultural factors. The top ranked sites were then presented to members of the Swinomish Tribe, who were asked to give their preference for location and desired use for the clam garden.

Survey data showed that tribe members plan to use the garden primarily for ceremonial and subsistence harvest and teaching intergenerational knowledge. Commercial harvest and research were identified as secondary priorities. Greiner says, “The more we learned about this ancient practice, the more we realized that this was an ideal climate adaptation strategy that addressed all concerns of the [tribal] community.

“The [tribal] community is concerned, not only about the future loss of traditional harvest sites from sea level rise and impacts to the health of shellfish due to the changing water conditions, but the subsequent loss in intergenerational knowledge sharing, food security, and identity.”

Courtney Greiner, clam garden project manager for the Swinomish Indian Tribal Community

Clam gardens are constructed by erecting a rock wall at the extreme low tide line. This wall backs up sediment and creates a terraced habitat for clams at the optimal intertidal depth. Garden locations are carefully selected to be in regions of high clam recruitment, and the bed is actively tended by harvesters. The Swinomish Tribe says this practice supports food sovereignty and access to traditional practices for coastal tribes and First Nations threatened by the impacts of climate change.

Even as shellfish populations decline due to ocean warming, sea level rise, and acidification, research has shown that clam gardens increase the size and number of littleneck and butter clams, which are tribally important species. Clams help to filter the water, and cultivated beds have a higher composition of shell hash which may help reduce the local impacts of acidification by increasing pH and aragonite saturation states. These gardens are also biodiversity hot spots, studies show, and create habitat for urchins, sea cucumbers, and kelp, among other species.

The Swinomish Fish and Game Commission and the Tribal Senate gave final approval for the site selected. In September 2021, the Tribe held a groundbreaking ceremony and blessed the site and formal construction began on August 12th of this year. The team has also completed a clam garden monitoring plan, which will measure the long term socio-cultural and ecological impacts of the project. This knowledge will help inform other groups interested in clam gardens as a method to combat climate change on a local scale.

In preparation, the Swinomish Tribal Community has been facilitating opportunities for members to experience a clam garden by organizing trips to British Columbia. Greiner says the Swinomish clam garden will soon provide all community members with a space for cultural and subsistence practices, and intergenerational knowledge sharing.

This article was based on findings presented at the 2022 Salish Sea Ecosystem Conference.