The construction of dams on rivers worldwide has stopped the natural flow of sand and silt to the sea—resulting in coastal wetland loss and disappearing beaches—as well as preventing fish from reaching vital spawning grounds. But when the decision is made to remove a dam it can be remarkably challenging. Just ask the people of Ventura, California, who’ve been trying for 20 years—and are not much closer to ditching a dam that supplies no water but packs a lot of downsides—and risk.
Wetlands on undammed waterways can cover as little as 2% of the landscape but hold 15% to 30% of the carbon. But if reservoirs hold all the water, those riparian areas will dry up and lose the ability to hold carbon.