Sea Otters: an appetite for protection

3 min readJan 23, 2021

Sea otters [Enhydra lutris] are an endangered species that reside along Pacific Ocean coasts. Otters have the densest fur of any animal and consume about ¼ of their body weight daily to keep warm, as they lack insulating blubber. Otters were extensively targeted and hunted for their fur until roughly only 1000 individuals remained. Today, otters are strictly protected by the Wildlife and Countryside Act of 1981 — but remain under threat from; habitat destruction, pollution, global warming, food shortages from overfishing, and poachers.

Kelp are “as important to oceans as trees are to land”, providing food, refuge and reproduction sites for a rich marine community. Around 800 marine species make use of kelp forests; ranging from bristle worms to jellyfish to grey whales. Further, algal growth here can be utilised as biofuel. If left unsupervised, urchin will fell kelp forests — diminishing kelp density, distribution and evicting species which reside there.

Paine (1969) first proposed the concept of Keystone species, defined as “species which have a disproportionately large effect on its environment relative to its abundance”. Dr Estes (1970s) discovered that otters were crucial to the health of kelp forests, through keeping down the number of sea urchins that would otherwise spread across the seafloor like a plague, relentlessly devouring kelp — and thus, are keystone species. Estes (1998) further found that killer whales’ dietary shift towards sea otters in southwest Alaska caused reverting in nearshore ecosystems from kelp forests to urchin-dominated states and instigated trophic cascades throughout the ecosystem. Countless studies have shown you cannot have kelp forests and corresponding rich biodiversity without sea otters there to protect them. Figures 2 and 3 below show the vast difference in benthic ecosystems with and without presence of otters.

Sea otters allow kelp ecosystems to flourish, facilitating NPP of 313–900g C m² yr¹ — having a stored carbon value of $205 — $408million on the European Carbon Exchange. For comparison, urchin barrens have NPP of 25–70g C m² yr¹. This supports Hairston’s (1960) green world hypothesis, whereby predators may substantially influence the carbon cycle through limiting herbivores and protecting autotrophs. In this sense, otters can be useful ocean ecosystem management tools. For example, 90% of a 200-mile stretch of kelp forest along California’s north coast was eradicated between 2014–2016. Through careful reseeding, urchin removal and reintroduction of sea otters to regulate urchin density, much of the forest is now beginning to regrow. Success is highly cause and extent-dependant, but this provides a glimmer of hope that Sea otters — and their heroic appetite — may be indispensable in maintaining crucial biodiverse ocean ecosystems, but also limiting global temperature rise amidst rapid climatic changes.