UCSC study shows how urchin-loving otters can help fight global warming

Can an abundance of sea otters help reverse a principal cause of global warming?

Hearty appetite allows kelp forests to thrive and absorb CO2

A new study by two UC Santa Cruz researchers suggest that a thriving sea otter population that keeps sea urchins in check will in turn allow kelp forests to prosper. The 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, the study finds.

The theory is outlined in a paper released online today (September 7, 2012) in Frontiers in Ecology and the Environment by lead authors UC Santa Cruz professors Chris Wilmers and James Estes.

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

Wilmers, Estes, a professor of ecology and evolutionary biology, and their co-authors, combined 40 years of data on otters and kelp bloom from Vancouver Island to the western edge of Alaska’s Aleutian Islands. They found that otters “undoubtedly have a strong influence” on the cycle of CO2 storage.

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.

Kelp is particularly efficient at sequestering CO2 from the atmosphere through photosynthesis. CO2 concentration in the atmosphere has increased 40 percent since the beginning of the industrial revolution, causing global temperatures to rise, the authors write.

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.