Climate Change & Sea Level Rise
This unprecedented restoration effort, in the middle of a major urban center, is transforming a landscape the size of Manhattan into a thriving wetland ecosystem and providing a critical natural buffer against the effects of global climate change and sea level rise.
The Wetland Sponge Effect: Part of a Long-Term Solution to Flooding Around the Bay
The expansive tidal wetlands that once circled the edge of San Francisco Bay served as natural buffers against flood events. Unfortunately, San Francisco Bay has lost more than 85% of its tidal wetlands. Once established, newly restored wetlands act as giant sponges, helping to absorb floodwaters during storm events and slowly releasing runoff back into the Bay.
Because of historic land subsidence in Silicon Valley, some of California’s most valuable business real estate is at risk of tidal flooding. The Restoration Project is improving former salt pond berms and levees and coupling them with tidal marshes on their outboard side. As they establish, these outboard tidal marshes will help protect the levees from storm wave action and tidal surge, benefiting human communities behind them.
Restored tidal wetlands also increase the flood carrying capacity of local creeks, flood control channels, and rivers. By slowly scouring and opening up the mouths of these waterways and reestablishing their connection to historic flood plains, new tidal marshes will help maintain existing flood control infrastructure.
Tidal Marshes Grow as Sea Levels Rise
Tidal marshes develop as sediment flows in and accumulates in newly opened salt ponds, and when the new tidal plains are the right elevation, vegetation begins to establish. These new marshes help offset the effects of sea level rise.
The South Bay is an excellent place for sediment deposition, and this bodes well for the development of new tidal marsh. Studies have shown that marshes in the South Bay remained intact, even between 1940 and 1960 -- a time when sea level was already rising and the land was subsiding rapidly due to groundwater extraction in Santa Clara County.
Once tidal marshes are established they become very efficient sediment traps. In effect, they tend to preserve themselves by growing higher as they age, provided that enough sediment is available in the Bay. For this reason new tidal marsh areas are likely to keep pace with changing sea level conditions.
Tidal Marshes Capture Carbon
Because tidal marshes are such biologically productive habitats, they capture large amounts of carbon from the atmosphere. Unlike many freshwater marshes, tidal saltwater marshes release only negligible amounts of methane, a powerful greenhouse gas. As a result, the carbon storage benefits of tidal salt marshes may exceed those of freshwater marshes. Tidal marshes may be more efficient per unit area than trees when it comes to removing carbon from the atmosphere.
Given enough sediment, tidal marshes continue to grow and pull carbon dioxide out of the atmosphere as sea levels rise. While specific research is needed to quantify the carbon sequestration capacity of the South Bay Salt Pond Restoration Project, there is no doubt that restoring tidal marsh is an effective method for removing carbon dioxide from the atmosphere and helping to reduce the effects of climate change.