The key to this challengeFerence is linked to the voracious appetite of sea otters. In order to maintain their high bolic rates, mammals must eat constantly. Among their favorite foods are sea urchins, which are easy to catch and high in calories. When present, sea otters eat so many sea urchins that the invertebrate population remains low. "They have a disproportionate impact on the ecosystem compared to their abundance," says Heidi Pearson, marine biologist at the University of Southeast Alaska. This is what makes them a "keystone " species - without their presence the stability of the entire ecosystem can be lost.
Sea otters have a voracious appetite, eating about a quarter of their body weight each day (Credit:)
When sea otters disappear from an ecosystem, the number of sea urchins increases. The herbivorous sea urchins then clearcut the kelp, chewing on the spikes at their base and sending the rest of the giant algae to wash. With this goes the habitat of many species, including fish, invertebrates and other mammals.
Sea urchins remain even after cutting through kelp beds. They go into a state of sleep, biding their time under new kelp shoots, then spring into action to eat the young algae. These invertebrates are known as "sea urchin zombies" for this ability. If the sea otters return, however, their feast may put the herbivores in check and allow the kelp to thrive again.
But these perpetually hungry mammals don't just protect ecosystems. of kelp. Sea otters can also enjoy seagrass beds. In these areas, otters feed primarily on crabs. When mustelids reduce the number of crabs, the grazing organisms that crabs eat rebound. These slugs and snails often do not eat seagrass beds; instead, they scrape off the algae that grows on the grass, allowing the algae to absorb more sunlight and grow more efficiently. “They don't miraculously eat the herbaria,” says Hughes. "They have this little radula that gently scratches [the algae] and removes all the epiphytes that grow on it. And don’tc it mainly protects the algae. "
In the Elkhorn Slough estuary in California, eelgrass had almost disappeared by the early 1980s due to the decline in the quality of the seaweed. 'water - nutrient pollution from farms increased algae growth, smothering seaweed. But since the return of otters, eelgrass has grown by more than six times .
And in these two ecosystems , otters could have the added benefit of storing carbon.
In 2012, a team of environmentalists including Estes published a study on the carbon sequestration potential of sea otters in the North Pacific between the Aleutian Archipelago and Vancouver Island. Using data on kelp growth rate and density at sites wi and without otters, they found that the presence of ottersof sea in rocky reef habitat in the study area, covering 51,551 square kilometers (19,900 square miles - an area roughly the same size as Costa Rica), is capable of storing 4.4 to 8.7 million tonnes of carbon compared to if an otter- free state. This is more carbon than that emitted by a million passenger cars for a year.
In areas where sea otter populations thrive, kelp forests often flourish too - they grow at a rate of up to 60 cm (24 inches) per day (Credit:)
Even before the sea otter effect was studied, kelp was seen as a possible climate solution. This is because he can growe very quickly - up to 60 cm (24 inches) per day. This means that it extracts carbon from the atmosphere faster than a slower growing plant (although kelp is technically an algae). When the kelp dies and washes off the shore, the carbon returns to the atmosphere during decomposition. But when dead kelp sinks to the bottom of the sea, it may not surface (and therefore decompose and produce carbon dioxide) for thousands of years. "A kelp sling that drifts to the seabed and decomposes, this carbon could be trapped in the sediment for millennia, if not millions of years, " says Pearson.
The carbon that is thus sequestered - barred from entering the atmosphere for 100 years or more - may be the key to tackling the climate crisis. But how much carbon in kelp is sequestre is still unknown. Part of the problem is the gas-filled bags along their stems. When the kelp dies, it tends to stay floating until these little floats break. "When these kelp are dislodged, they can travel and circulate on the surface for 1,000 km [620 miles]," says Hughes.
In addition to kelp forests, the otter effect on seagrass can also benefit the climate. Like kelp, seagrass beds absorb carbon as they grow and store much of this carbon in its roots. And when the older roots die, the carbon gets stuck in the sediment, where it can take hundreds of years or more to convert back to its gaseous form. “When I think of marine plants that can sequester carbon very well, it's usually rooted plants,” says Hughes. "So I'm talking about seagrass, swamps and mangroves - this will bet the bi g three carbon sequestration habitats, in my opinion. "
Even at a lower estimate, sea otter carbon sequestration may add up. If only 1% of the kelp between the Aleutians and Vancouver Island is stored in the high seas, this is still enough to offset the emissions from 100,000 combustion automobiles . And if otters continue to bounce back in their historic range, it would increase that carbon store - and all the ecosystem benefits of otters. "When we help restore missing key predators, we create things in many ways before we even recognize some of these ways," wrote Lillian Carswell, Southern Sea Otter Recovery Coordinator for the US. Fish and Wildlife Service, in an email to Hfrance.fr.
But reintroducing otters is notIt's a win for everyone. Their massive small ap may reduce the possibilities fishing for commercial operations and indigenous subsistence communities.
Quantifying the effect of otters could help mitigate some of the impacts on fishing. Based on the December 2012 price on the European Carbon Exchange ($ 47 [£ 36] per tonne of carbon), the Estes document that year estimated that the presence of sea otters in their area North Pacific study was d 'worth up to $ 408 million (£ 296 million) . Carbon prices have since climbed, exceeding recently the 60 € (£ 51/71 $) per ton ,which would bring this estimate even higher in the current market. And a 2020 study found that the monetary benefit of sea otters - due to their restoration of kelp habitat and the associated increase in fish stocks, carbon sequestration and ecotourism value - outweighs shellfish fisheries losses .
Maybe some win-win strategies to bring This key species exists. One idea the researchers have pitched is to use the money from the carbon offsets generated by the otters for compensate fishermen for the loss of their catches . If the value of the otter's carbon bank is recognized by our human banks, perhaps mustelids will soon cross more reefs.and estuaries - tackling climate change while they're at it.
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