How do sea otters help kelp forests flourish?

Sea otters play a vital role in maintaining the health of kelp forests through a process known as a trophic cascade. As apex predators, sea otters primarily feed on herbivorous sea urchins, which are known to consume the holdfasts of giant kelp and other kelp species.123

By preying on these urchins, sea otters keep their populations in check, preventing them from overgrazing the kelp. When urchin populations are left uncontrolled—often due to the absence of sea otters—they can decimate kelp forests by eating the structures that anchor the algae to the seafloor, causing the kelp to detach and float away.13

This predation by sea otters allows kelp forests and the diverse fish populations associated with them to flourish, demonstrating the significant influence these mammals have on the stability and biodiversity of coastal marine ecosystems.12