How Sea Otters Support Marine Conservation and Climate Action

Sea otters, a vital part of kelp forest ecosystems, could help facilitate habitat conservation efforts, and even slow down global warming.

Sea otters are considered a “keystone species,” and for good reason. According to the U.S. Fish and Wildlife Service, a keystone species is one that “has an effect on its environment disproportionate to its abundance.” That is, only a few individuals can greatly impact its ecosystem. Sea otters are practically a textbook example of this, and recent research has shown that the way that they impact their own ecosystems could have far-reaching effects, revealing their potential role in combating global warming.

Sea otters play a critical role as apex predators in kelp forest ecosystems. Their fast metabolism and lack of blubber requires them to consume 25% – 30% of their body weight daily, enabling them to control the numbers of their prey species. This dietary demand enables them to regulate populations of various prey species, including crabs, clams, mussels, and, most significantly, sea urchins.

Sea urchins feed on kelp, the foundational species of kelp forests. When unchecked, sea urchins can decimate these underwater forests, leading to barren seascapes devoid of the biodiversity that kelp forests support. By preying on sea urchins, sea otters maintain a delicate ecological balance, allowing kelp forests to thrive and continue their vital ecological functions.

Prior to the start of the sea otter fur trade, which began around 1790, sea otters were estimated to have numbered up to 300,000 individuals. However, by the early 1900s, sea otters had been hunted to extinction in around 85% of their habitat—a loss that marine wildlife continues to suffer from today.

Kelp forests, with their towering strands that can reach up to 175 feet, provide shelter for countless marine species, from a variety of invertebrates and fish to sea lions to gray whales. These underwater forests also serve as natural barriers, slowing ocean currents and protecting smaller marine life from predators like orcas. However, without sea otters to control sea urchin populations, kelp forests are replaced by “urchin barrens”—barren seascapes devoid of the shelter and biodiversity once provided by thriving kelp ecosystems. Without predators to curb their numbers, sea urchins overwhelm the ocean floor, preventing kelp forests from regrowing.

Kelp forests are supposed to be home to a variety of marine life. Without the shelter from larger predators and the ocean current that it provides, these species all suffer and are left in danger of serious decline, or even extinction in some cases.

(Photo reprinted from Word of Mouth Magazine)

An urchin barren in Noyo Harbor, CA.

While these impacts on kelp forests and their marine life is nothing short of devastating, the fact is that kelp forests are in no way isolated ecosystems—in fact, they could even be part of our solution to global warming.

Carbon sequestration is the process of capturing and storing carbon dioxide from the atmosphere. Kelp forests can do this at dramatic rates. According to an article by Harvard University, “[c]oastal ecosystems … can sequester up to 20 times more carbon per acre than land forests.” These ecosystems include (but are not limited to) kelp forests. When the plants that make up coastal ecosystems die, they are buried and due to low oxygen concentration underwater, they can stay buried in the coastal seafloor for decades before they break down and release carbon dioxide into the atmosphere. 

Sea otters not only enable this to happen, but they even raise the amount of carbon dioxide that kelp forests can sequester by helping them to thrive. According to a study published by The Ecological Society of America, kelp forests with sea otters present absorb over 12 times the amount of carbon dioxide as kelp forests without sea otters.

Based on this research, restoring sea otters to kelp forests where they have been absent could significantly enhance these habitats’ role in combating climate change. Their reintroduction has the potential to slow global warming and, in the future, play a crucial role in offsetting it entirely, contributing to a carbon-neutral or even carbon-negative world.

Sea otters are not only vital to the balance of their ecosystems but also to the broader natural world’s efforts to mitigate climate change. However, they’re still considered endangered and their overall population is still decreasing.

While many populations around the world have begun to recover from the impacts of the fur trade, populations in the northern and southern portion of their mainland range are still actively declining. The southwest Alaskan sea otter population, for example, declined by nearly 90% between 1990 and 2015.

Currently, the main culprits of this overall decline is still human behavior. Though the original decline was caused by the species actively being hunted for their fur, the byproducts of our behavior are one of the biggest issues today.

Pollution such as chronic oil spills – which result from industrial accidents and recreation boats leaking oil – and urban runoff weaken otters’ immune systems, causing them to be significantly more susceptible to disease. This pollution has a lasting impact on otter populations, affecting reproductive success and overall survival rates.

Increased contact with domestic animals has also given rise to an increase in disease overall. Diseases such as toxoplasmosis, Sarcocystis neurona infections, and phocine distemper virus come from fecal matter, which sea otters are more likely to be exposed to as a result of their diet that is partially made up of filter feeders (e.g. clams) which do not eliminate these parasites.

(Photo reprinted from The Washington Post)

A large oil spill off the coast of Southern California that occurred in 2021.

Climate change itself also causes issues in the way their prey and predators behave. As the ocean both warms and becomes more acidic, prey distribution can change. These changes result in prey scarcity that impacts both sea otters’ food availability, and some predators (such as orcas or sharks) even relocate to areas with sea otters due to this food scarcity and begin to incorporate them into their diet.

Finally, habitat loss urgently threatens sea otters as well. Coastal development, marine traffic, and fishing have all led to a loss of their home. Accidents such as boat trikes and even entanglement in fishing gear also directly endanger these populations, worsening the situation further.

Sea otters have made significant progress in their recovery since the end of the fur trade and due to their position as such a valuable species to our world, we need to continue this trend.

As keystone species, they play a crucial role in maintaining the delicate ecological balance of both their own habitats and the greater world through their impacts on climate change. By regulating sea urchin populations, sea otters indirectly contribute to carbon sequestration and climate change mitigation. However, human activities, including pollution, disease, climate change, and habitat loss, continue to threaten their survival today.

To ensure the future of this remarkable species and the ecosystems they support, it is imperative to prioritize conservation efforts and reduce human impact on this vital species. By protecting sea otters, we can safeguard the health of our oceans and contribute to a more sustainable future.