Sea otters are a keystone species that maintain kelp forest health by preying on sea urchins.

Sea otters hunt sea urchins, which are voracious grazers of kelp. When otter populations decline, urchin numbers explode and they can devour entire kelp forests, leaving behind urchin barrens that support far less biodiversity. With otters present, urchin populations stay low, allowing kelp to grow dense and complex. These kelp forests provide habitat, food, and nursery grounds for countless fish, invertebrates, and marine mammals, dramatically increasing coastal productivity and resilience.