Are sea otters secretly climate crusaders?

09/12/2012 04:34:56 PM PDT

By Jason Hoppin – Santa Cruz Sentinel
SANTA CRUZ – Monterey Bay's main mascot may turn out to be a secret agent in the fight against climate change.
It has long been known that sea otters, nursed back from brink of extinction in the past several decades, provide huge benefits for the vitality of undersea kelp forests. But a pair of UCSC scientists recently found that those benefits extend into the atmosphere, finding a strong connection between otters, kelp and global warming.
"We just looked at the question, 'Does it matter?'" said James Estes, a UCSC biologist. "And the answer was yes."
In a paper published in the October issue of Frontiers in Ecology and the Environment, Estes and UCSC environmental studies professor Chris Wilmers found that if otters covered the globe, the resulting growth in kelp forests would strip 10 percent of the carbon dioxide from the atmosphere.
"We discovered that in a world with otters versus a world without otters, the effect was significant," Estes said.
To put that in context, carbon dioxide levels have gone up 40 percent since the Industrial Revolution. Otters would solve a quarter of that problem.
The actual impact is significantly lower, isolated to regions where otters are found. Sea otters range along the West Coast of North America, with the number off California estimated at just more than 2,700.
The broader lesson of the paper is how the species can impact an ecosystem, potentially playing an important role mitigating climate change.
"You don't think of predators walking around influencing the carbon cycle," Wilmers said.
The authors went so far as to estimate sea otters' value in term of carbon credits, noting their impact would be worth between $205 million and $408 million on the European Carbon Exchange.
The process begins with one of otters' favorite snacks: sea urchins.
The word "urchin" has a negative connotation for a reason. They can be ravenous creatures, moving in packs across the ocean floor and destroying as much as 30 feet of kelp forest a month.
A key limitation on their population is otters, with the relationship between otters and healthy kelp forests having long been recognized – more otters mean more kelp.
Similar to terrestrial forests, kelp removes carbon from the environment, and is being studied for its environment impact. Scientists are building an underwater platform called the Kelp Forest Array near Hopkins Marine Station in Pacific Grove, partly to study climate change and human impacts on marine ecosystems.
Studies also have shown that domesticated animals can hurt the environment. Methane from cows, for example, has been shown to be similar to human-linked carbon emissions as a threat to the ozone layer.