It may sound absurd to
think that sea otters could be a key to combating global warming. But it’s
true. The findings of a new study on the subject even floored UCSC’s Jim Estes,
one of the study’s leading researchers.
“I was blown away. We got all the data together,
looked at the results, and I was like, ‘Whoa! Are you sure? Go back and run
those numbers again.’”
But in the end, it
checked out. Suddenly, sea otters were every conservationist’s dream come true. After 40 years of collecting data, UCSC
researchers Estes, Chris Wilmers and their colleagues had uncovered a new link
between the universally adored furball and what many consider Earth’s most
imminent danger.
Estes and Wilmers
studied sea otters and their effect on kelp beds in a region stretching from
Vancouver Island to the edge of Alaska’s Aleutian Islands. After comparing
otter-dense and otter-scarce areas, they found that kelp flourished in the
former.
“It blew my mind. It was just incredible to see
these two completely different ecosystems as a consequence of loss of sea
otters,” says Estes.
Equipped with data on
kelp density and net primary production
(measured in units of carbon absorbed per area, per time), and the rate at which kelp absorbs CO2,
Estes and Wilmers only needed to piece them all together.
“It was really a very simple, almost
back-of-the-envelope calculation. It was just doing all the accounting to know
how much carbon is there with and without sea otters,” says Wilmers.
With an appetite for
kelp-destructive sea urchins, hungry otters yield thicker kelp beds which, in
turn, absorb more carbon from the atmosphere. Otters on the hunt force sea
urchins into hiding and allow the kelp beds to thrive, photosynthesize and
essentially suck out copious amounts of CO2. This top-down, predator-prey
effect is known as a trophic cascade, and is the basis of the suspected
connection between predators and the cycling of CO2. If predators suppress
herbivores, plants prosper and stimulate the carbon cycle, decreasing CO2 in
the atmosphere. Essentially, it’s environmental dominoes.
The study found that
kelp beds with a robust sea otter population had up to 12 times the absorbance
capacity than kelp in sea-otter scant regions. In fact, if the entire planet was
composed of a sea otter-kelp ecosystem, sea otter-induced carbon reduction
would rank solidly in the 5-10% range.
Though this incredible
correlation paints sea otters as something of a furry superhero, they can’t do
it alone. With sea otters as their poster-child, Estes and Wilmers’ study
illuminates the global effect apex predators can have on the carbon cycle.
“From a global perspective, the effect of sea
otters is miniscule, but it points to the fact that predators can have a pretty
dramatic effect in their own ecosystem,” says Wilmers. “There are predators
everywhere, so globally, the effect of predators can be pretty significant.” Their research suggests that, while a
predator-prey balance is key in species interactions, it more importantly
underlies the collective harmony of our ecosystems’ carbon cycle.
After finding the
astounding sea otter-carbon correlation in the ocean, many researchers have
turned their attention to land, searching for sea otter-analogous predators in
a terrestrial ecosystem. Wilmers himself is looking into that possibility,
targeting wolves as a focal point for his potential future research.
