The ocean is a vital ally in this existential venture. Blue carbon ecosystems (BCEs) — which include mangroves, tidal and salt marshes, seagrasses as well as open ocean food webs and nutrient cycles — have enormous capacity to store carbon within the plants, animal biomass and in the sediments below for long periods of time. BCEs are an essential part of the global drive to counter climate change, protect biodiversity and enhance livelihoods by capturing carbon and keeping ocean and freshwater systems healthy and productive to help ensure sustainable future.