Researchers from Sonoma State University in California observed that the return of sea otters could halt the degradation of coastal marshes in their region. The findings were published in a leading science journal, underscoring the role of top predators in shaping marshland resilience and coastal ecology.
Sea otters feed on striped shore crabs, small arthropods whose digging and rooting disrupt the soil structure. When these crabs overexploit the roots that bind soil, the marsh floor begins to degrade, creating patches that resemble Swiss cheese. Rain and wave action then erode the exposed land, accelerating habitat loss for a variety of marsh-dwelling species.
The ecological balance began to shift again after sea otters gradually recolonized their historic range. Historically, these mammals roamed the North American coastline from Alaska down to California. Their numbers plummeted in the 19th century as overhunting for fur reduced populations to roughly two thousand individuals worldwide.
Following a combination of hunting protections and habitat restoration efforts, otters began to reestablish themselves in former habitats, a process that spanned more than a hundred years. California’s coast saw the first reliable detections of sea otters in 1984, marking a significant milestone in the recovery of this keystone species.
Researchers note that sea otters contribute to the recovery and maintenance of kelp forests by preying on sea urchins, which otherwise devastate underwater kelp gardens. By controlling urchin populations, otters help safeguard kelp canopies, which provide critical habitat for hundreds of species. The study’s broader message is clear: deliberate reintroduction and protection of key species can strengthen the health and stability of entire ecosystems.
In addition to ecological benefits, the researchers discuss potential considerations for future conservation planning, such as monitoring predator-prey dynamics and addressing the lingering threat from northern white sharks, which pose a risk to otter populations in some coastal areas. The findings emphasize that a holistic view of ecosystem dynamics—where predators, herbivores, and habitat-forming organisms interact—can guide effective restoration and conservation strategies across coastal Canada and the United States.