Sea Otter Repopulation Efforts Add More Benefits Than Costs

Sea otter in British Columbia. (Photo courtesy of James Thompson)

(CN) — Sea otters in the Pacific Northwest are experiencing a resurgence after being hunted to near extinction by the 18th and 19th century fur trade, bringing with them profound benefits to the local environment and economy.

A new study, published Thursday in the journal Science, offers the first localized cost benefit analysis of recent sea otter recovery efforts around Vancouver Island. One of the study’s goals is to contrast the economic benefits from increased ecotourism and biodiversity with the loss of fishing habitat to both commercial and indigenous fisherman.

“Our work offers a glimpse into a future where otter populations have recovered to an estimated 5000 animals, and have fully reoccupied their historic range,” said lead author Edward Gregr, an adjunct professor at the the University of British Columbia’s Institute for Resources, Environment and Sustainability.

“We found that coastal ecosystems with otters present are almost 40% more productive. In the long run, that equates to higher fish catches worth $7 million, carbon storage worth $1.5 million and tourism opportunities worth $31 million per year.”

Sea otters are great for the environment. They primarily eat the same sea urchins that graze on carbon-sequestering kelp forests. Carbon sequestration is the process by which plants remove CO2 from the atmosphere or oceans and store it for their own use.

Kelp reduces carbon dioxide by fixing free CO2 particles through photosynthesis, and since kelp can grow at two feet per day, 30 times faster than most trees, they sequester huge amounts of CO2 and represent one of the best allies we have in combating climate change.

Sea otter presence has been found to increase yields of ecosystem biomass by 37%, while adding $1.6 million per year in carbon sequestration value based on European Union carbon tax pricing.

“Kelp forests provide habitat to many species and can enhance both biodiversity and resilience,” the study’s authors say. “The otter-present system would thus seem to support a more resilient social ecological system.”

Sea otters wield an outsized influence over their habitat. After being reintroduced to the Pacific Coast in the 1970s, these creatures have begun to transition the local ecosystem back toward its natural equilibrium. Though, this often brings them into conflict with humans competing for the same resources.

“As keystone species, top predators can exert strong effects over the function, structure, and diversity of ecosystems. When these species recover after extirpation, they often reestablish top-down control and shift the ecosystem closer to an unexploited state,” the authors note.

In the past, local fisherman caught an abundance of valuable invertebrates such as Dungeness crabs, geoduck clams and urchins at arm’s length in shallow water fishing grounds, all of which an increasing number of sea otters are now vying for. The study predicts shallow water crab habitats will be mostly lost, while deeper water habitats, where the otters cannot reach, will thrive.

The loss to invertebrate fisheries is calculated to be $5.4 million, while the geoduck clam catch is predicted to decline by 25%, along with a 28% reduction in the value to Manilla and butter clam fisheries. However, the authors estimate the increased value of local fin fish to be $6.9 million, offsetting some of the damage to the commercial fishing industry.

The competition with sea otters for valuable invertebrates will be felt most acutely by indigenous fisherman.

While commercial fisheries can more easily adapt by employing improved technology and seeking their catch in deeper waters, indigenous peoples with their more restricted harvesting areas cannot adjust so easily as they lack the deep-water fishing boats, technologies and capital that commercial fisherman enjoy.

They are also less likely to enjoy the tourism benefits from a resurgence in sea otter populations than other coastal communities.

“Until the 2000’s I think it’s fair to say that it was possible to make a subsistence living from invertebrates, salmon and ground fish,” Gregr said. “But fish stocks have been significantly depleted, especially salmon and herring. Today, it’s next to impossible. An elder told me a year or so ago, that ‘without the Coop, we would starve.’”

The changes in ecosystem value have been calculated based on estimates of four services: fisheries catch and landed value, tourism choices, carbon pricing and estimates of trophic transfer efficiency.

“It’s clear that humanity must reverse the decline in biodiversity if we want to achieve a sustainable future,” said co-author Kai Chan, a professor at UBC’s Institute for Resources, Environment and Sustainability and its Institute for the Oceans and Fisheries at UBC. “This study demonstrates that restoring key species to ecosystems can also have great benefits for people, and could serve as a useful framework for evaluating top predator recovery elsewhere.”

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