Sea otters are the most advanced greedy ecosystem engineers. In order to stay warm and healthy, they eat a quarter of their body weight every day, and dive into the seabed repeatedly to collect bivalves such as sea urchins, crabs and clams. “In order to survive in their environment, they have to eat as much as possible. They have a very dramatic impact on these habitats, and they are very active,” Fujii said. (Another project further along the coast of California tries to bring back a different kind of “Sea Urchin Killer“——Human diver.)
Controlling the number of sea urchins can protect kelp, which is critical to the ecosystem in two main ways. First of all, forests are habitats for fish, and fish are food sources for other marine mammals such as birds and sea lions. Second, seaweed is what scientists call “Blue carbon“Ecosystem refers to coastal or marine areas that can store carbon. (Other areas include wetlands with mangrove forest.)
But it is tricky to quantify exactly how much carbon a healthy seaweed forest consumes. For example, a red cedar tree has grown very large for hundreds of years, locking up a large amount of carbon for a long period of time. (Unless it on fireIn this case, the carbon will return to the atmosphere. ) The changes in underwater things are even greater. All kinds of small animals, including sea urchins, are eating kelp-and emitting carbon. In addition, the churning ocean destroys debris from the forest, which falls to the bottom of the sea and decomposes, releasing stored carbon. As a result, seaweed forests continue to decay and re-grow, sequestering and releasing carbon.
It is difficult to determine how long the carbon has been trapped. “The fate of all these kelp is still unclear,” Wilmers said. “Imagine that everything that is falling off sinks into the deep ocean and will not reappear in 1000 years. This is a more important carbon storage benefit than just falling off and immediately decomposing and returning directly to the atmosphere.”
Considering this uncertainty, Wilmers did some estimate Potential carbon benefits of healthy otter populations further north on the Pacific coast, between the Canadian border and the tip of the Aleutian Islands. If a seaweed forest grows well, half of the carbon absorbed is stored in the deep ocean, which is equivalent to reducing the emissions of 5 million cars. Even if only 1% of the carbon remains deep, it is equivalent to the emissions of 100,000 cars.
In Monterey Bay, otters not only protect kelp.They also ventured up to the large tidal swamp Elkhorn Slough, where they encouraged the growth of eelgrass, another coastal plant that sequesters carbon-although otters can affect plants A more indirect wayOtters eat crabs, and crabs eat invertebrates such as sea slugs. Sea slugs eat algae that grow on eelgrass. Reducing the number of crabs that prey on slugs actually helps eelgrass, because when slugs remove algae, it keeps plants clean, allowing them to absorb more sunlight.Due to the return of otters, the number of eelgrass in Elkhorn Slough has increased Jumped 600% In the past three decades.