To mark World Otter Day, we examine these fascinating animals – and their unexpected role in climate and ecosystems. Kelp forests are among the most important natural carbon sinks in the oceans. Although peatlands or terrestrial forests store larger absolute quantities, kelp grows extremely rapidly, continuously sequestering CO₂ from the atmosphere in the process.
This mechanism is particularly effective in areas inhabited by the sea otter (Enhydra lutris). Studies indicate that kelp forests with otters can sequester between 4.4 and 8.7 million tonnes more CO₂ than those without otters. This is due to the sea otter preying on sea urchins and other invertebrates. In areas without otters, sea urchins can multiply unchecked, decimating the kelp forests and drastically reducing their carbon storage capacity. By regulating sea urchin populations, otters indirectly maintain the functionality of kelp forests.
A healthy kelp forest containing otters yields further benefits: the biomass of fish and other organisms increases by up to 37%, which in turn benefits fisheries – with potential annual net gains calculated at approximately 9.4 million Canadian dollars. Furthermore, sea otters promote ecotourism: their presence alone can generate annual revenues of up to 41.5 million Canadian dollars for coastal regions.
Otters belong to the mustelid family and, despite their charismatic appearance, are carnivorous predators. Their fur is the densest in the entire animal kingdom, with up to 160,000 hairs per square centimetre – roughly equivalent to the total number of hairs on a human head. Unlike other marine mammals, otters lack an insulating layer of blubber. The dense fur alone protects them from the cold water temperatures of the North Pacific, which rarely rise above 20 °C.
Otters exhibit intelligent behaviour: they use stones as tools to crack open their preferred prey, sea urchins. Some otters even store a favoured stone in a pouch of skin on their abdomen. Research also suggests that otters possess long-term memory and can transmit knowledge to conspecifics. A well-documented social behaviour is "rafting" or holding paws while sleeping on the water's surface, which prevents them from drifting apart.
Sources:
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