Salt Marshes

Salt marshes are coastal wetlands that are flooded and drained by salt water. They are extremely important to the coastal environment because they provide nourishment for young fish, crabs, and shrimp and prevent flooding during storms. They are found all over the world, though salt marshes in different regions have different species of plants and animals.

Salt marshes are composed of deep mud and peat (decomposing plant matter). Oxygen levels in the peat are extremely low, a condition called hypoxia, and this is caused by growth of bacteria. It makes salt marshes smell like rotten eggs occasionally.

Contribution for the environment

In many ways, salt marshes are like the sponges of the coast. They are able to filter and soak up water before it reaches the ocean. They filter excess nutrients and run-off to maintain water quality in bays, as well as prevent flooding during a storm by being a natural buffer. They also are “carbon sinks” by holding carbon that would otherwise be released in the atmosphere and contribute to global warming.

Salt marshes also serve as a shelter for young fish, crabs, and shrimp. In fact, 75% percent of the species in fisheries rely on salt marshes. The roots, stems, and leaves of salt marsh plants help protect and nourish these creatures and are the producers in the salt marsh food chain. Plants are decomposed by bacteria, algae, and fungi, which are sources of food for many fish, crabs, and shrimp. In turn, the feces of those animals can act as fertilizer for plants. The animals are also preyed on by birds such as herons and egrets.


Unfortunately, salt marshes are threatened by pollution and climate change. Runoff containing petroleum and fertilizers pollute the environment as well as harm animals, which in turn can affect the entire food chain.

Salt marshes suffered many losses in the 20th century from habitat loss. In addition, it is estimated that between 2004 and 2009, salt marshes lost about 80,000 acres per year. The cause of this is from sea level rise, pollution, more frequent storms, and erosion.

The San Francisco Estuary is the largest expanse of salt marshes on the west coast of the United States. The Bay’s wetlands can be split into three groups: the mudflats, the salt marshes, and the brackish marsh. Mudflats are at lowest elevations, where the mud is too salty to be able to support plant life. Salt marshes are at a higher elevation, where the soil is drained of saltwater enough that plants are able to survive. The plants that live there can survive in the saline soil by secreting salt on their leaves. Finally, the brackish marsh is where saltwater and freshwater converge. The boundaries of mud flats, salt marshes, and brackish marshes are not clear because they are constantly shifting due to storms and the tides.

Above: a wetland in golden gate national recreational area in San Francisco

The San Francisco Estuary is also home to multiple native and protected species, for example, the California clapper rail and the salt marsh harvest mouse. However, it is currently in danger of being wiped out. It is estimated that it has lost about 90% of its area since naturalists first arrived in 1816. The 90% of the area was lost because it was diked off and used to build cities such as Oakland and Berkeley, or used to build farms and salt extraction facilities. It is also suffering from multiple invasive species and rising sea levels due to climate change.

Fortunately, there are initiatives that are trying to restore the San Francisco Estuary. The South Bay Salt Pond Restoration Project, started in 2002 and headed by the State of California, has a goal to restore 90% of salt ponds to wetlands. It does this by managing and keeping track of ponds, as well as building levees to prevent flooding and building areas of higher ground to combat sea level rise. Currently, it is the largest wetland restoration project on the west coast.

What can you do?

Although the situation does not sound optimistic, there are still many things you can do to help salt marshes. These include:

  • Supporting restoration projects- you can vote to support funding for restoration

  • Spreading awareness and knowledge about salt marshes

  • Reducing the use of pesticides and fertilizers, which can harm wildlife

  • Removing non-native or invasive species when you see and walk past them in a salt marsh

  • Keeping storm water run-off clean

  • Cleaning up pet/ animal waste if you find it in wetlands


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