Study shows how sea otters can reduce CO2 in the atmosphere


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

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 , and their co-authors, combined 40 years of data on otters and kelp bloom from to the western edge of Alaska’s . 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 “ 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, 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 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 can affect ecosystems abilities to sequester carbon.

Written By: Guy Lasnier
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  1. Urchins don’t actually graze on the kelp but they do chew on the roots which anchor it to the rocks.

    I don’t know enough to comment on whether this could really have much impact on global warming but it certainly does damage the kelp forest’s ecosystem- from the microscopic, all the way up to the fish, seabirds,sea lions, harbor seals and whales, which both feed and take shelter from storms in the forest. This was proved in the early 20th century when otters were hunted almost to extinction, allowing urchin populations to go unchecked, and whole kelp forests disappeared.

  2. Every little helps!   Like reducing the destruction of rainforests, preserving photosynthetic absorption of CO2  helps keeps the cycle in balance.

    The individual small patches do not individually contribute much to the global cycle, but they all add up to a global system.

  3. The sea-otter sea-urchin kelp populations over time have swung drastically.  I have seen video of the sea bottom in what they call “urchin barrens” – bare rock with no sign of even a blade of kelp. One of my favourite life experiences was an IMAX movie of a kelp forest.  It was just alive with life on every pixel of the screen.

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