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Blog: The importance of restoring the Bay’s wetlands

Marshlands at the Don Edwards Wildlife Refuge.

Posted on October 2, 2023

Once, nearly 200,000 acres of wetlands ringed the edges of San Francisco Bay. By the mid-20th century, only 10% remained. Why are Bay wetlands essential, and what is being done to restore them?

The importance of Bay wetlands

For much of history, wetlands were regarded as useless wasteland, neither dry land to be farmed or built on nor open water that could be used for shipping. The aim for Bay wetlands – whether marshes or mudflats – was to either drain them for agriculture (and eventually, for development) or dike them off for salt production.

It wasn’t until recent decades that people began to realize how important wetlands are for the health of the Bay. Tidal marshes are nurseries for many wildlife species that seek the shelter of marshlands for breeding; they provide habitat for threatened and endangered species such as the tiny salt marsh harvest mouse and the elusive bird known as the Ridgway’s rail. Tidal marshes are also incredibly efficient at absorbing carbon from the atmosphere; they sequester two to four times as much carbon as a tropical rainforest and also filter pollution from stormwater before it enters the Bay. Finally, both tidal marshes and mudflats protect against sea level rise and storm surges more effectively than complex infrastructure such as engineered levees.

Fortunately, although many historic wetlands have been converted to development, thousands of acres can still be restored, and efforts are underway to make that happen. This is possible because many of the Bay’s wetlands, especially in the southern part of the Bay, were not significantly altered but merely diked off with low earthen levees so that seawater could be piped in and allowed to evaporate for salt production. Many of these salt ponds are now part of the Don Edwards Wildlife Refuge or otherwise publicly owned and are being restored to healthy tidal marsh and tidal mudflat and pond habitat as part of the South Bay Salt Pond Restoration Project.

We need to restore many more wetlands for the health of the Bay

Although tens of thousands of acres of Bay wetlands have been restored, we need tens of thousands more to protect the health of the Bay. But we are running out of opportunities to easily and inexpensively restore former wetlands. The only former wetlands that can easily be restored are those that remain basically unaltered, such as salt ponds – and few remain.

Among the salt ponds that could easily be restored to wetlands are those located in Redwood City, owned by the Cargill corporation. These Cargill salt ponds span over 1400 acres on the east side of Highway 101 from Woodside Road to Marsh Road, and if restored, could provide not only critical habitat for wetland species but would also protect at-risk communities in North Fair Oaks and along Bayshore Road from the threat of sea level rise.

Unfortunately, the Cargill corporation has shown itself more interested in trying to convert these former wetlands to development than in allowing them to be restored. In the early 2000s, Cargill proposed a development the size of the city of San Carlos on the Redwood City salt ponds but was forced to withdraw the application after massive opposition from community members and environmental groups. Then during the Trump administration, Cargill managed to get a federal determination that the salt ponds were not subject to the Clean Water Act, only to have that determination overturned in court.

Since any development on the Redwood City salt ponds would not only result in the permanent destruction of restorable wetlands but would also result in homes being built close to heavy industries and in the path of sea level rise, Cargill would be well advised to abandon any attempts to develop the salt ponds and instead allow them to be restored to tidal wetlands. Such an action would protect communities instead of putting them at risk and would create critically needed wetland habitat for threatened and endangered species instead of destroying it.

Come and visit our Bay wetlands!

One final benefit of Bay wetlands: they are beautiful open space areas right on our doorsteps. Come and see how many different species of shorebirds and waterfowl you can spot! Migration season for birds is coming up, and the Bay is a significant stop on the Pacific Flyway, meaning that we’ll soon be seeing all sorts of birds from faraway places breaking their journeys in the Bay wetlands. You can visit Bair Island in Redwood City or the Don Edwards Wildlife Refuge in Alviso or Fremont to see what a healthy tidal marsh is like!


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