September 8, 2012

Study: Sea Otters Can Help Reduce CO2

April Flowers for - Your Universe Online

How can sea otters change the world?

A new study, led by the University of California, Santa Cruz, suggests that a thriving population of sea otters will keep the sea urchins in check, which will in turn allow kelp forests to prosper.  Spreading kelp forests can absorb as much as 12 times the amount of CO2 from the atmosphere than if it were subject to sea urchin ravaging.

"It is significant because it shows that animals can have a big influence on the carbon cycle," said Chris Wilmers, assistant professor of environmental studies.

The study, published in Frontiers in Ecology and the Environment, combined 40 years of data on otters and kelp bloom from Vancouver Island to the western edge of Alaska's Aleutian Islands.  The team found that otters "undoubtedly have a strong influence" on the cycle of CO2 storage.

By comparing kelp density with and without otter populations, they found that sea otters have a positive indirect effect on kelp biomass by preying on sea urchins, a kelp grazer." When the otters are in proximity, urchins hide in crevices and satisfy themselves with kelp scraps.  When the otters are gone however, the urchins devour the living kelp voraciously.

Sea otters are marine mammals, from the weasel family, native to the coasts of the northern and eastern North Pacific Ocean. Sea otters feed by diving to the ocean floor to forage.  They prey mainly on sea urchins, mollusks and crustaceans, and a few species of fish. They are considered a keystone species, or a species that has a disproportionately large impact on its environment, because the otters control the sea urchin population, allowing the kelp forests ecosystem to thrive.

CO2 levels have risen nearly 40% since the beginning of the industrial revolution, causing global temperatures to rise.  Kelp is extremely efficient at sequestering CO2 through photosynthesis and removing it from the atmosphere.

The team acknowledged that increasing otter populations will not solve the problem of higher CO2 in the atmosphere, but they 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 added.

In the realm of global environmental conservation, mitigating CO2 levels in the atmosphere is a pressing issue with many obstacles and no easy solutions.  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 sequestration.

The authors 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."