SF's Living Seawall Brings Marine Life Back to the Bay

When a crew lifted specially designed concrete tiles from San Francisco Bay last July, they found something remarkable: what started as bare gray squares had transformed into bustling underwater neighborhoods teeming with seaweed, oysters, limpets, and crabs.

This three-year experiment marks the first step in an ambitious plan to rebuild San Francisco's aging seawall in a way that puts marine life first. The project is a collaboration between the Smithsonian Environmental Research Center and the Port of San Francisco.

The current seawall stretches three miles along the Embarcadero and was built between 1878 and 1915. It's showing its age, and rising seas make the need for upgrades urgent. During high tides, water already floods around the Ferry Building, the lowest point along the waterfront.

Traditional concrete seawalls are smooth and steep, dropping quickly into deep water. They support very little life compared to natural shorelines, which slope gradually and create spaces where creatures can attach, hide, and grow.

"We can add features that make it better habitat, such as adding texture, or shelving or small tidepools, which promotes a greater diversity of species," explains Dr. Andy Chang, one of the project's lead scientists. More biodiversity means healthier ecosystems for everything from tiny plankton to fish, birds, and marine mammals.

The pilot project tested three types of tiles in different parts of the Bay. Some were standard concrete, some used a special eco-friendly concrete mixture but stayed smooth, and others used the same eco-friendly concrete but featured ridges and small shelf-like bumps.

The textured eco-friendly tiles were the clear winners. They attracted colorful Turkish towel seaweed, rainbow seaweed, and various shellfish. This matters because thriving native species can better resist invasive threats like brown kelp and European green crabs.

The concrete itself makes a difference too. Standard industrial concrete is toxic to marine life and contributes to carbon emissions during manufacturing. ECOncrete, the company that provided the special mixture, estimates that 70 percent of the world's marine infrastructure is built from concrete, creating a massive impact on coastal ecosystems.

The Ripple Effect

San Francisco isn't inventing this idea from scratch. Seattle's Elliott Bay already uses living seawall technology successfully, proving the concept works along the West Coast.

The approach offers a powerful two-for-one solution: protecting human communities from flooding and erosion while creating thriving habitats for marine life. As sea levels continue rising, coastal cities worldwide will need to upgrade their infrastructure anyway, so why not do it in a way that helps rather than harms ocean ecosystems?

Brad Benson, the Port's waterfront resilience program director, says a natural waterline would have "a sloped, gradual area where you can have robust, intertidal growth and activity." While San Francisco can't completely recreate that natural slope, adding habitable features to the rebuilt seawall gets much closer to that ideal.

The success of these humble concrete tiles shows that climate adaptation and ecosystem restoration don't have to be competing goals.