Fortresses of mud: how to protect the San Francisco Bay Area from rising seas

There’s something apocalyptic about this pond on the east side of San Francisco Bay, California. The legacy of a salt industry that has moved elsewhere, it has subsided a couple of metres below the level of neighbouring marshland. Algae paints red swirls in the brown water, and the pond’s edge is crusted hard with sparkling salt. As a breeze eases off the bay, a squadron of pelicans sails by, en route to more-appetizing hunting grounds.

But there is a better future ahead for landscapes like this one in the Eden Landing Ecological Reserve and elsewhere around the bay. Over the next decade, government officials plan to fill many such depressions with sediment and then open them up to the tides. Eventually, cordgrass, pickleweed and other marsh vegetation will take root, restoring this crucial marsh ecosystem. The goal is to try to create a natural buffer to protect the heavily populated waterfront, by sapping energy from storm surges and blocking the highest tides.