Whale Fall (after life of a whale) from Sharon Shattuck on Vimeo.

You’ve probably heard coral reefs compared to rain forests. When it comes to the diversity of life they support, it’s an accurate analogy. But when it comes to carbon storage and cycling, whales – not corals – are the trees of the ocean. Over their long lives, they can lock up tons of carbon in their immense bodies. Then, when they die, the carcasses fall to the sea floor, transporting that carbon to the deep sea.

Not all of that carbon immediately sinks into the sediment to be trapped for eternity. Instead, much of it is recycled – composted, as it were – by deep-sea scavengers. As the video above shows in graphic, if somewhat euphemistic, detail, whale carcasses are ecosystems unto themselves.

Still, it’s thought that whales are a major player in the ocean’s ability to trap carbon away from the atmosphere. A study published last year concluded that restoring all whale populations to pre-industrial levels would remove approximately 160,000 tons of carbon each year – the equivalent of preserving over 2,000 acres of forest. What’s more, the authors said that rebuilding whale and large fish populations would provide greater carbon-capture benefits than widely debated ocean fertilization schemes, without the uncertainties and ecological risks.

National Oceanic and Atmospheric Administration (NOAA)

This map shows the predicted abundance of life on the sea floor, based on an analysis of data from the Census of Marine Life. In the most 'alive' areas, the life on 20 square feet of the ocean floor holds as much carbon as the average American emits in one year.

When I first looked at NOAA’s Image of the Day today, my response was an underwhelmed: “Pretty, but what does that mean?” The explanation that accompanied the image was pretty jargon-heavy. Basically, what I gathered is that a team of researchers used data from the decade-long, international Census of Marine Life project to develop a model of how much life – from bacteria right up to fish – lives on the sea floor. Since all life on Earth is carbon-based, the researchers boiled everything down to the equivalent weight in carbon. Because they’re scientists, they used metric system – milligrams and meters, instead of pounds and feet (we’ll also skip the argument about whether or not the whole world should go metric). And because some parts of the seafloor are essentially dead while others are teeming with life, they used a logarithmic scale that allowed them to span a range from less than an ounce to over 10 tons. Still, I had little way of putting “11 tons of carbon per square meter” into perspective.

So I did some quick conversions and cross-referencing, and here’s what I came up with: In the most ‘alive’ areas (those are the dark green ones, like right off the coast of New England), the life on 20 square feet of the ocean floor holds as much carbon as the average American emits in one year.

It’s estimated that a third of global carbon dioxide emissions are absorbed by the ocean. Some stays in the water (where, incidentally, it can wreak havoc on fundamental ocean chemistry), while some is sucked in by marine plants and turned into the stuff of life. Little fish eat the plants, big fish eat the little fish, and eventually, animals die and sink to the seafloor (those that live on the seafloor, obviously, don’t have far to fall), taking all their carbon with them. Some will get intercepted along the way or eaten by scavengers on the seafloor (we’ll call it carbon recycling), but some of that carbon gets buried in the mud – where it may remain locked away for centuries. The ability of the ocean to absorb and trap carbon dioxide away from the atmosphere has been called “blue carbon,” and it’s just one of many arguments for conserving and rebuilding ocean life threatened by overfishing, habitat destruction, and pollution.

But it’s a double-edged sword. As you may recall, a rather grim State of the Ocean report released earlier this week concluded that ocean life faces the distinct possibility of a wave of extinctions unprecedented in human history. Skyrocketing carbon dioxide levels are (will be) largely responsible for that. In other words, excessive carbon dioxide threatens one of the planet’s greatest defenses against said excessive carbon dioxide. Climate scientists might describe that as a “negative feedback” – in my opinion, a rather dry term for a morbidly fascinating Catch-22.

Not surprisingly, the State of the Ocean report has snagged a fair bit of media attention. Rather than reinvent the wheel, I’ll leave you with closing thoughts from others.

Bryan Walsh, EcoCentric (TIME):

Despite the scary IPSO reports — and scores of others like it that have been published in the past — the oceans seem likely to continue to get less attention than they need and deserve. Maybe that’s because we’re fundamentally land-based creatures. Anyone can see a clear-cut rain forest and know that something was lost, but on the surface, a living sea and a dead one look much the same. We used to think the oceans were far too vast for mere humans to affect — but we should know that’s not the case any longer. Earth is often tougher than we think, but if we don’t do something, we really do risk irrevocably altering the blue in our blue planet.

Read more –>

Andy Revkin, Dot Earth (NY Times):

With some wise management and a bit of operating space, it’s pretty clear from the new analysis that the oceans splendid inhabitants can thrive for a long while to come.

The question remains whether humans can find a way to apply wise practices to shared resources that lie outside conventional boundaries.

Read more –>

flickr/slack12

Salt marshes, sea grass beds, and coastal mangrove forests can sequester five times as much carbon as tropical forests.

You’ve probably never heard of “blue carbon.” Don’t feel bad. You’re not alone. But it’s worth getting acquainted with.

Basically, it’s the idea that ocean and coastal ecosystems can absorb and trap carbon dioxide that contributes to climate change. In fact, over at SciAm, Robynne Boyd explains that mangrove forests, salt marshes, and sea grasses can hold five times more carbon than tropical forests that typically get more attention.

Because they hold so much carbon, destroying them can release substantial amounts of CO2. People around the world wreck coastal habitats through aquaculture, agriculture, timber extraction and real estate development. To date, human encroachment has destroyed more than 35 percent of mangroves, 30 percent of sea grass meadows and 20 percent of salt marshes.

Stopping such destruction could therefore become an important element in confronting climate change. “Blue carbon is a source of emissions that hasn’t been addressed by the climate community and therefore creates an opportunity to reduce emissions,” says Roger Ullman, executive director of the Linden Trust for Conservation in New York City, which promotes the use of conservation finance and environmental markets. “These fabulous ecosystems…don’t cover a very large expanse of territory, yet still provide enormously important services to humanity and are being destroyed three or four times faster than the rate of tropical forests.”

If Boyd’s introduction to the science and policy of blue carbon piques your interest, check out Steven Lutz’s Blue Carbon Blog – a great source of news on the topic.