Sea otters and kelp: a tale of cute charisma and otterly amazing climate heroism

One look at a sea otter, and it’s easy to understand why for so many it’s love at first sight. Their charming demeanor and fluffy faces beckon as they snack and float on their backs. But more than their apparent cuteness, sea otters are critical players in marine ecosystems and a keystone species, meaning they have a profound effect on their ecosystem. Sea otters are vital to kelp forests, ensuring the health and carbon storage abilities of these important ecosystems.

So, while they are exceptionally cute, sea otters are worthy of adding an additional accolade to their roster—climate hero.

Here’s how otters help the planet:

Superpower: sustaining kelp forests

Sea otters and kelp have developed a close partnership over the years. Sea otters will wrap themselves in kelp, or use it as an anchor, when feeding or resting while floating together in what are known as “rafts,” or groups of over 10 individuals. Researchers have even found that sea otters are able to escape shark bites more easily when swimming among heavier kelp canopies.

A big part of the sea otter’s diet consists of crabs, barnacles, and sea urchins. All of these creatures live in kelp forests. However, when left unchecked, creatures like sea urchins can grow exponentially, devouring the kelp before it can replenish. This could have important implications as the climate changes. Coastal ecosystems, including kelp forests, play important roles in sequestering atmospheric carbon. In other words, kelp captures and prevents carbon from entering the atmosphere. Healthy kelp can absorb significant amounts of carbon dioxide from the atmosphere and is a key contributor to “blue carbon,” which is the carbon stored in oceans. Kelp forests are capable of storing up to 20 times more carbon per acre than forests on land. Studies suggest that seaweed forests, including kelp forests, globally can sequester tens of millions of metric tons of carbon every year in the deep ocean, which is about the same as half a million acres of trees. When kelp dies and sinks to the bottom of the ocean to decompose, part of the carbon it was storing is trapped in the sediment of the ocean floor for approximately 100 years.

A destroyed or degraded kelp forest is a major loss. The loss of kelp can have considerable consequences on carbon levels in the atmosphere. That’s because sequestered carbon is key to addressing climate change. To keep these ecosystems healthy, it is critical that their threats are removed. And that starts with ensuring that kelp eaters are kept in check. This is where sea otters enter. Sea otters play a significant role in supporting kelp forests and their ability to capture carbon by feasting on the critters that would otherwise voraciously consume the kelp.

Superpower: a small hero with a big appetite

They make look like restful loungers, but sea otters actually have high metabolisms that require a lot of fuel and as much as 25%–30% of their body weight in daily food. There are few other animals that eat this much relative to their body weight. Some of their favorite foods include clams, mussels, crab, and sea urchins, the last of which is the antagonist and top predator for kelp.

Sea urchins are spiky, ball-like creatures that sweep across the ocean floor feasting on kelp. They can also multiply rapidly. But luckily for sea otters, sea urchins are easy to catch and pack a caloric punch. Sea otters will ravenously feast on the sea urchins, thus controlling their population and keeping their numbers from getting high enough that they would threaten kelp survival.

Without sea otters, sea urchin numbers would spike, and the stability of this ecosystem would collapse. Sea urchins would graze through the kelp forest, chewing away at the base and sending the rest of the kelp fronds to wash away—and with them, all the species that live in the kelp forests. Sea urchins will even stick around and eat any new, young kelp sprouts that are taking hold.

A dynamic duo in need of support

More research is still needed to determine the full extent of just how animals can be important drivers and influencers of carbon storage and to quantify the understanding of this role. But what is known is that key wildlife species, like sea otters, are critical in their food webs and ecosystems, creating opportunities for addressing climate change through more effective management plans that consider land-use and the role of wildlife.

Sea otters were once widespread from the waters of Baja California to Alaska to the reefs of Japan and Russia. However, they were hunted to the brink of extinction through the 1800s due to the fur trade. Thanks to conservation efforts, their numbers have been slowly rebounding, even though sea otters are still missing across over 2,000 miles of coastline from their historical range. It was this loss that illustrated the critical role that sea otters have on kelp forests. While diving in Alaska in the 1970s, marine ecologist James Estes documented how kelp forests can become underwater deserts without sea otters around.

The sea otter–kelp forest partnership is an illuminating example of just how intertwined and connected nature and climate are. But this relationship can also have serious implications when considering the reverse—a changing climate warms and acidifies the ocean, which leads to the decline of kelp cover, and by extension, threatens the survival of sea otters.

Sea otters and kelp forests are a dynamic duo that exemplify how nature and healthy ecosystems provide a multitude of benefits, including carbon capture. And if we focus efforts on protecting sea otters, we get closer to ensuring healthy kelp forest and marine ecosystems, and ultimately a more balanced and healthier climate and planet.