Coastal habitats, including mangrove forests and sea grass beds, cover only a small fraction of the world’s surface, but these fringe ecosystems harbor an enormous amount of carbon. Organic matter — the decaying remains of once-living plants and animals — becomes trapped by the roots of aquatic plants. Over time, this carbon-rich detritus builds up, sometimes to depths as great as 10 feet, representing hundreds of years of accumulation.
By some estimates these habitats and their so-called blue carbon stocks — in the soil and the plants themselves — store up to five times more carbon than tropical rainforests the same size.
Just as preserving forests offers a chance to sequester carbon and curb climate change, preventing the disruption of coastal habitats, which are often razed for development or aquaculture, ensures that their deep carbon deposits are not released into the atmosphere as carbon dioxide.
Blue carbon markets, in which countries or corporations could offset CO2 emissions by buying carbon credits from projects that create or protect carbon-rich habitat, could become viable in two to three years, says John Bruno, a marine ecologist at the University of North Carolina in Chapel Hill. “It’s something really tangible that has a triple bottom line: It’s good for the environment, good for people, and it’s profitable,” says Bruno, who studies carbon sequestration rates of mangroves in Muisne, Ecuador.