Not far from Seattle skyscrapers live 150-year-old clams, more than 250 species of fish, and underwater kelp forests as complex as any terrestrial ecosystem. For millennia, vibrant Coast Salish communities have lived beside these waters dense with nutrient-rich foods, with cultures intertwined through exchanges across the waterways. Transformed by settlement and resource extraction, Puget Sound and its future health now depend on a better understanding of the region’s ecological complexities.

Focusing on the area south of Port Townsend and between the Cascade and Olympic mountains,...