Mangrove forest, Indonesia. (© Joel Vodell)

If there is a last line of defense against climate change, it may well lie in the mangrove trees that cling to coastlines throughout the tropics.

Locked in the mud of these unique tidal forests is thousands of years’ worth of accumulated carbon. Clear the mangroves — as humanity has been doing ever faster in recent years — and that carbon is slowly released into the atmosphere, where it accelerates global warming.

Fast-growing and incomparably capable of storing carbon in their soils, mangroves thrive in salty waters, where their hearty root systems form a barrier against erosion and provide a haven for wildlife. Communities that live among healthy mangroves benefit immeasurably from the upsides that mangroves provide — from acting as buffers against waves and storms to providing a nursery for fish, crab and clam species that are crucial parts of coastal diets and livelihoods.

Yet in the battle to prevent the worst effects of climate change, this last line of defense is thinning.

Barely half of the world’s original mangroves remain, most of them having been cleared in the past half-century for farms and other development. The short-term payoff of clearing a stretch of mangroves pales next to the impact on the climate: The carbon footprint of a steak and shrimp dinner — were it to come from shrimp farms and pasture formerly occupied by mangroves — is the same as driving a small car across the continental United States, a recent study found.

Luckily, local efforts to protect these habitats — and other marine and coastal wetlands including seagrasses and salt marshes, collectively known as “blue carbon” ecosystems — have taken root. In northern Brazil, for example, Conservation International is assisting a local community in protecting its mangrove forests through sustainable crab-fishing cooperatives, which have doubled workers’ income in just a year.

Unfortunately, local conservation efforts are on their own not enough to turn the tide. Until the global community understands the full value of mangroves to humanity, these trees will continue to be felled for short-term gain. We have to make it worth it to invest in protecting these areas.

ging the business model
On the mangrove-rich Caribbean coast of Colombia, Conservation International is working to do just this. Later this year, a mangrove conservation project here will become the first-ever blue carbon initiative to be issued carbon offsets under the widely adopted Verified Carbon Standard.

What this means, simply put, is that commitments made to keep these mangrove forests intact can be purchased and traded on the global market to compensate for carbon emissions made elsewhere in the world. As public pressure grows on companies to account for their impacts on nature, carbon offsets — in short, nature itself — can become a larger part of the solution.

Up to now, mangroves have been underused in international carbon markets compared with terrestrial forests, despite the fact that they can store up to 10 times more carbon per hectare than terrestrial forest. Broadening these projects to include more mangroves provides a bigger climate mitigation impact, while offering more climate adaptation benefits through economic incentives that can be used to protect coastal communities who stand to lose the most due to sea-level rise.

The stability of our climate is being protected by a thin green line. We cannot afford to lose it.

ʻAulani Wilhelm is senior vice president of Conservation International’s Center for Oceans. 

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This content was originally produced by The Economist Group’s World Ocean Initiative and hosted on our website. 

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