Managing for intact ecosystems could help mitigate greenhouse gas impacts
By Summit Voice
SUMMIT COUNTY —Maintaining healthy sea otter populations could put a dent in the seemingly unstoppable build-up of heat-trapping carbon dioxide in the Earth’s atmosphere, according to a pair of UC Santa Cruz researchers.
Of course, the new study doesn’t suggest that otters alone can stem the tide of global warming, but shows how maintaining functional natural ecosystems could play a role in mitigating the effects of greenhouse gases.
Here’s how it works: Otters control sea urchin populations. Sea urchins eat kelp, and fast-growing kelp is very efficient at absorbing CO2. After studying 40 years of data on otters and kelp bloom from Vancouver Island to the western edge of Alaska’s Aleutian Islands, the researchers found that spreading kelp can absorb as much as 12 times the amount of CO2 from the atmosphere than if it were subject to ravenous sea urchins.
Otters “undoubtedly have a strong influence” on the cycle of CO2 storage, Chris Wilmers and James Estes wrote in a paper published inline in Frontiers in Ecology and the Environment.
“It is significant because it shows that animals can have a big influence on the carbon cycle,” said Wilmers, assistant professor of environmental studies.
Comparing kelp density with otters and kelp density without otters, they found that “sea otters have a positive indirect effect on kelp biomass by preying on sea urchins, a kelp grazer.” When otters are around, sea urchins hide in crevices and eat kelp scraps. With no otters around, sea urchins graze voraciously on living kelp.
Wilmers and Estes acknowledge that a spreading otter population won’t solve the problem of higher CO2 in the atmosphere but argue that the restoration and protection of otters is an example how managing animal populations can affect ecosystems abilities to sequester carbon.
“Right now, all the climate change models and proposed methods of sequestering carbon ignore animals,” Wilmers said. “But animals the world over, working in different ways to influence the carbon cycle, might actually have a large impact.
“If ecologists can get a better handle on what these impacts are, there might be opportunities for win-win conservation scenarios, whereby animal species are protected or enhanced, and carbon gets sequestered,” he said.
Mitigating increased CO2 in the atmosphere is a pressing issue in global environmental conservation with many obstacles and no easy solutions, the authors wrote. They note that markets have been established in Europe and the United States to trade carbon credits and thus inject an economic incentive into either reducing CO2 output or increasing CO2 sequestration.
They estimate that the CO2 removed from the atmosphere via the otter-kelp link could be worth between $205 million and $408 million on the European Carbon Exchange.
“An alluring idea,” they write, would be to sell the carbon indirectly sequestered by the sea otter protected kelp forest “as a way to pay for their reintroduction and management or to compensate losses to shell fisheries from sea otter predation.”
Wilmers and Estes were joined by Matthew Edwards, San Diego State University; Kristin L. Laidre, University of Washington; and Brenda Konar, University of Alaska.