Know Your Roots

Mangrove forests help keep our heads above water—and marine protected areas help them help us.

September 18, 2015

Mangroves are pretty rad. These trees that appear to rest on the water’s surface have extensive root systems that not only help protect coastlines from storm surges but can also store massive amounts of carbon for millions of years.  

Protecting these forests that protect us is a good idea. A new study from Duke University scientists has found that conservation measures in Indonesia—home to the world’s largest area of mangrove forests—prevented the loss of around 35,000 acres of mangrove habitat between 2000 and 2010. By leaving these forests alone, about 13 million metric tons of stored carbon didn’t get released into the atmosphere. Coauthor Brian Murray, from Duke’s Nicholas Institute for Environmental Policy Solutions, compared this to taking 344,000 vehicles off the road annually for each year the forests were left alone.

Like seagrass, salt marshes, and other coastal vegetation, mangroves store what’s called “blue carbon”—basically carbon sequestration under the sea. Mangrove forests are some of the most carbon-rich ecosystems on the planet, with more biomass per acre than most other types of forests. The trees grow atop layers of carbon-rich peat. While submerged, this soil doesn’t rot. But when you destroy a mangrove forest—whether by pollution or by converting it into a shrimp farm—you kick up the peat soil and unleash its carbon load.

Mangrove forests aren’t monitored very well, but a recent World Wildlife report shows a global decline of 20 percent between 1980 and 2005. The Duke study’s main focus was determining what strategies worked best at keeping mangrove forests, and the carbon trapped within them, intact.

The researchers compared the effectiveness of two types of conservation zoning: marine protected areas (MPAs) and species-management protected areas (SMAs). MPAs, such as biosphere reserves and national parks, cover entire ecosystems and permit no resource extraction within their borders. SMAs, meanwhile, protect specific species and their habitats and allow some resource extraction. Mangrove forests, by the way, are home to many endemic and threatened species, such as proboscis monkeys, water mice, smooth-coated otters, and fishing cats—the list is long and incredible and strange.

By looking at publicly available data sets, the scientists found that in Indonesia, SMAs had no appreciable impact on mangrove loss and carbon emissions, while MPAs avoided the emissions of 13 million metric tons of carbon. There are nearly three times as many MPAs than SMAs in Indonesia, which may account for some of the difference, but in the end, it makes sense that saving the whole ecosystem is better than rescuing a species or two within it. More MPAs, please. 


onEarth provides reporting and analysis about environmental science, policy, and culture. All opinions expressed are those of the authors and do not necessarily reflect the policies or positions of NRDC. Learn more or follow us on Facebook and Twitter.

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