San Francisco Bay Salt Ponds, Salt evaporation ponds in San Francisco Bay, California, US

The San Francisco Bay Salt Ponds form an extensive network of shallow basins where seawater evaporates to create salt through natural processes. The system spans thousands of acres and is connected by channels and levees that control water movement between pools.

The Ohlone evaporated bay water in natural tide pools before the Gold Rush brought industrial salt making in the 1850s. Small family operations were later absorbed by the Oliver Salt Company at Mount Eden and Leslie Salt in Newark. Cargill bought Leslie in 1978, and in 2003 sold most ponds for the South Bay Salt Pond Restoration Project.

The Ohlone made salt by evaporating bay water in natural tide pools, and salt production dates to the time when they were the area's only inhabitants. The ponds later became a core ecosystem for over a million waterbirds, including canvasbacks, ruddy ducks and snowy plovers on the Pacific Flyway.

Access is through the Don Edwards San Francisco Bay National Wildlife Refuge and adjacent bay trails; guided tours explain salt production and the South Bay Salt Pond Restoration Project. Ponds are fenced off for safety and wildlife, so stay on levees and marked paths. Winter and spring migration brings up to 200,000 birds to a single pond.

The ponds shift in color from green to pink as the salt concentration increases and water stays longer in the basins. This striking change happens because specific microorganisms thrive in highly salty water and tint the pools with their pigments.