What ecological role does the sea otter famously play in kelp forests?

The sea otter famously acts as a keystone predator in kelp-forest ecosystems.

Sea otters eat sea urchins, crabs, clams, and other invertebrates. By reducing sea-urchin grazing, they can help kelp forests persist, creating shelter and feeding areas for many additional species. This is a classic example of a trophic cascade, in which changes at one feeding level affect an entire community.

The term keystone species does not mean the animal is always the most numerous or largest predator. It means its ecological influence is disproportionately large relative to its abundance. Where sea otters disappeared, intense urchin grazing contributed to “urchin barrens” in some regions.

Sea otters also have exceptionally dense fur and rely on grooming and metabolic heat rather than a thick blubber layer for insulation. Their ecological effects vary with local predators, prey, and habitat conditions.