Ours is a water world. Though Earth has a land-centric name, oceans cover 71% of its surface and make land livable. Some of the planet’s most critical processes happen where sea and air meet, as the oceans absorb and redistribute heat and carbon—both rising due to the glut of emissions in the atmosphere. Oceans have absorbed at least 90% of the excess heat generated by recent climate changes, and, since the 1980s, have taken up 20-30% of human-created carbon dioxide. The latter happens through the biological processes of photosynthesis and building calcium carbonate shells, and through simple chemistry, as carbon dioxide dissolves in seawater. Coastal and ocean sinks bring 17% of all heat-trapping emissions back to Earth.
NOTE: Oceans take up 23% of the carbon dioxide emissions pumped into the atmosphere each year. When we consider other greenhouse gases, including methane, nitrous oxide, and fluorinated gases, oceans remove approximately 17% of total emissions. (Global Carbon Project analysis adjusted to include all greenhouse gases at 100 year global warming potential.)
While this uptake of heat and carbon has buffered the planet from more severe climate change, oceans are paying a steep price. How so? Water temperatures, marine heat waves, and sea levels are rising. More carbon dioxide in seawater makes the ocean more acidic and less hospitable for shellfish to build shells or coral to build their skeletons. Oxygen levels in ocean water have already declined somewhat. In the future, biomass production through photosynthesis may also drop, destabilizing the base of the food chain. What’s more, with fewer organisms alive, fewer would die and sink into the deep ocean, carrying their carbon with them.
What practices can be used to sequester carbon in coastal, marine, and open ocean environments? How can human activity support and enhance natural processes? These questions are vital for addressing emissions but also for shoring up oceans’ life-sustaining role. Even as oceans suffer, they also are home to significant solutions. Solutions for coastal and ocean sinks center on ecosystem protection and restoration and improved agriculture practices.
- Protect and Restore Ecosystems. Protecting ecosystems—including mangroves, salt marshes, and seagrass meadows—supports ongoing photosynthesis and carbon storage. Because these “blue carbon” ecosystems have been lost or degraded in many places, restoration also has a vital role to play.
- Shift Agriculture Practices. Along coasts and in the open ocean, select regenerative practices may augment natural carbon sequestration from seaweed and kelp, while growing fiber and food from the sea.
Oceans will continue to be on the frontlines of climate change, as will people who live near them. Solutions focused on coastal and marine sinks can provide additional benefits from storm protection to healthy fisheries. It’s impossible to separate blue and green, land and sea. They, and we, are fundamentally intertwined.
NOTE: Project Drawdown has assessed a very limited selection of coastal and ocean solutions to date. This solution set will expand in the future (e.g., solutions for regenerative ocean farming and marine ecosystem restoration).