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PRI's Environmental News Magazine

Otters and Climate Change

Air Date: Week of September 14, 2012

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A sea otter in the Vancouver Aquarium (Photo: Imtiaz333 Flickr Creative Commons)

According to two scientists at the University of California at Santa Cruz, a small animal could have a big impact on climate change. Professor Chris Wilmers explains how sea otters could be key to preserving kelp forests, one of the world’s great carbon sinks.

Transcript

CURWOOD: It's Living on Earth - I'm Steve Curwood. Sea otters are cuddly, cute and playful, but a recently published report from the University of California at Santa Cruz claims they could hold one of the keys to mitigating climate change. Two scientists from UCSC have demonstrated the crucial role that sea otters play in the health of kelp forests, one of the ocean’s great carbon sinks. If we want to sequester more carbon from the atmosphere, they say, we need more otters. Joining us now from the University of California at Santa Cruz is Chris Wilmers, professor of Environmental Studies. Professor, welcome to Living on Earth.

WILMERS: Thank you, glad to be here.

CURWOOD: So, sea otters as climate warriors - what made you think to connect the otter with climate disruption?

WILMERS: Well, I do a lot of work on the effects of predators more generally on ecosystems. And one thing we’ve been seeing for a long time now is that predators can have a dramatic impact on plant populations through their intermediary impact on their prey. So, when otters eat sea urchins, which are their main diet for instance, we see kelp forest bounce back to life. And my research has also focused a bit on climate change and so I thought I wondered if there was a connection between the two.

CURWOOD: So, explain to me your study and the specifics of the findings that you have.

WILMERS: Well, over 40 years or so, my co-author and colleague Jim Estez has been looking at the effect of sea otters on coastal ecosystems. And what he’s shown over that time period is that when you have otters, you have these abundant kelp ecosystems. When you remove otters, the kelp forests disappear. And what’s novel about this study is that we looked at… how that influences carbon. And what we found is that there’s a dramatic draw-down of carbon from the atmosphere when you have sea otters and all that underwater kelp using that carbon.


Kelp beds protected by otters absorb 12 times more carbon dioxide than those that are thinned out. (Photo: Saspotato Flickr Creative Commons)

CURWOOD: And what’s the mechanism? I mean, the sea otters are related to urchins are related to kelp… explain that for me please.

WILMERS: So sea otters eat sea urchins. When you have sea otters around, you have fewer sea urchins and the ones that you do have - they sort of hide in the crevices between rocks. If you get rid of the sea otters, the sea urchins come out of the crevices, start crawling around on the sea floor, eating all the kelp they can find, their populations increase and the kelp declines to nearly nothing.

CURWOOD: So currently what is the population of sea otters and what would a healthy population look like?

WILMERS: Well, the area that we were doing our work is mainly the Aleutian Islands, but then also the coast of North America down to the Canadian/US border. And in that area, there used to be probably a few hundred thousand sea otters. That population has declined dramatically over the last 20 or 30 years by a somewhat mysterious switch in feeding patters by killer whales.

CURWOOD: Killer whales?

WILMERS: Killer whales, yeah! So, the theory is that killer whales used to eat primarily the large baleen whales. And after World War II there was a tremendous increase in whaling which depleted most of the large baleen whales over much of the north Pacific. So by the 70s or 60s there were very few baleen whales remaining.

And so the killer whales that remained switched to a new food source - and that turned out to be harbor seals. And then they depleted harbor seals so they switched to feeding on fur seals. And then they depleted fur seals and they switched to feeding on Steller sea lions. And, the depleted the Steller sea lion populations so finally the switched to feeding on otters. They drove the otter population down from a few hundred thousand to just a few thousand.

CURWOOD: So, intensive whaling is indirectly connected to more climate disruption.

WILMERS: Yeah, in a sense you could say that. There’s been a sort of chain of cascading events that initiated back in the 1950s with heavy whaling.

CURWOOD: Given the current population of otters and their appetite for sea urchins that would otherwise eat kelp, how much carbon do you think that they are helping stay sequestered - what might that be worth on the international carbon exchanges?

WILMERS: Well, we did a calculation in our study using the current price of carbon on the European carbon market. And we valued the carbon that sea otters indirectly sequestered using that value and it came out to be somewhere in between 205-400 million dollars, just in the carbon sequestered by the living kelps themselves.

CURWOOD: How might you use that dollar amount to affect the status of sea otters?

WILMERS: Well, the hope would be that you could use that money to reintroduce sea otters and restore the kelp forests. Right now, carbon markets are very young and they’re still evolving and I’m not sure that you could actually sell that carbon on the market today. But, as those markets evolve, we hope that there will be mechanisms to do that kind of thing and that kind of money could be used to figure out how to reintroduce otters or restore them to historic populations and get back all that carbon into the ocean.

CURWOOD: So, what do you hope will come out of this research?

WILMERS: I think one of the main things that I hope will come out of this research is the influence that animals can have on the carbon cycle. So far most of the carbon cycles don’t incorporate animals - they incorporate plants, certainly - but animals have been largely overlooked because it’s been assumed that they are bit players in the carbon cycle. But what I think this study shows is that the role of animals can be quite significant, and that ecologists more generally should be looking the world over for roles that animals might be playing in other kinds of ways in other kinds of ecosystems that influence the carbon cycle.

CURWOOD: Chris Wilmers is a Professor of Environmental Studies at the University of California at Santa Cruz. Thank you so much for taking this time today!

WILMERS: Thank you!

 

 

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