What are blue carbon ecosystems and why are they critical for climate?

The answer

Blue carbon ecosystems - mangroves, seagrass meadows, and tidal salt marshes - cover less than 2% of the ocean but store an estimated 50% of all carbon buried in marine sediments. Mangroves sequester carbon at a rate of 6 to 8 tonnes per hectare annually, compared to 0.2 to 0.5 tonnes for typical terrestrial forests. Seagrass meadows, covering roughly 300,000 square kilometers worldwide, store up to 830 tonnes of carbon per hectare in their root systems and sediments. Yet these ecosystems are disappearing at a rate of 2 to 7 percent annually - faster than tropical rainforests. When destroyed, they release centuries of stored carbon. The 2015 Paris Agreement recognized blue carbon's importance, and over 50 countries now include coastal ecosystems in their climate pledges.