What Is Life Without Transition? Why Estuarine-Terrestrial Transition Zones Matter

transition zone restoration
Save The Bay staff and volunteers are restoring this slope adjacent to a newly restored wetland at the Eden Landing Ecological Reserve.

The majority of Bay Area residents live and work within a half mile from the Bay, which makes the San Francisco Estuary one of the most urbanized estuaries in the world. Humans have valued the Bay for various ecosystem services throughout history and have modified the Bay to take advantage of some of those services. For example, humans have diked large areas of the Bay for commercial salt production and duck hunting, and have built trails close to the Bay so that they can enjoy the cultural services that the Bay provides. They have also hampered some of those services by filling and paving over large areas of the Bay to build urban infrastructure, and until the 1960’s, used the Bay as a place to dispose of garbage and sewage. It has only been the last several decades that the general public began to realize the importance of the natural ecosystem services the SF Bay provides.

San Francisco Bay was once ringed by healthy wetland habitats. Those wetlands, in many cases, gradually transitioned from tidal wetlands to upland terrestrial habitat. Those areas of gradual transition would often extend for a mile or more, comprising large expanses of native grasses and salt tolerant plants utilized by abundant wildlife populations. Over time, those transition areas have been squeezed between urban infrastructure and the Bay. These areas at the marsh-upland interface, that we call estuarine-terrestrial transition zones, are important because they provide important and unique ecosystem functions and services. Faced with climate change, transition zones can provide important ecosystem services, including buffering hazards associated with sea level rise such as flooding and erosion, and providing a place for wetlands to migrate inland. In addition, the transition zone provides nutrient cycling, filtration of pollutants from urban runoff, and support for biological diversity.

Save The Bay focuses its restoration effort on creating functional transition zone habitat in areas that lack transition zones. Using a carefully selected site-specific plant palette, we restore transition zone vegetation in areas such as the Eden Landing Ecological Reserve (ELER) in Hayward adjacent to recently restored salt ponds where transition zone habitat is lacking. Several of these former salt ponds are being breached to restore natural tidal flow as part of the South Bay Salt Pond Restoration (SBSPR) Project. Save The Bay has been working with the SBSPR Project at the ELER to vegetate the slopes adjacent to these ponds in order to provide functions such as high tide refuge and cover to avoid predation for marsh animals during high tides. Sign up for a volunteer program and join Save The Bay’s Habitat Restoration Team to learn more about functional transition zone habitat and important ecosystem services at our sites throughout San Francisco Bay.

Watch this PBS NewsHour clip about the importance of restoring transition zones for wildlife.