Tidal Salt Marshes

Learn why tidal salt marshes are important and what threatens them. Tidal salt marshes are extremely productive ecosystems, important ecologically and economically, and highly efficient at sequestering carbon. Yet they are underappreciated and need advocates and protectors.

• Along with mangroves and seagrass, tidal salt marshes are the “blue carbon” of the world, ecosystems that store more carbon per meter than forests—about fifty times as much carbon per meter per year, in the case of salt marshes.
• Thick-growing salt marsh grasses draw carbon from the air and store it in their extensive roots.
• Only a thin layer of soil in marshes dries out between tides. The rest of the soil remains saturated with water, which prevents dead roots and other organic material from decaying, keeping the stored carbon underground for the long term.
• Tidal salt marshes are important for many kinds of wildlife. They provide “seascape nurseries” for young fish and shellfish such as shrimp, blue crab, and salmon. Migratory birds find food and safe harbor in marshes on their travels. Endangered birds such as the salt marsh sparrow live only in salt marshes.
• In storms, tidal salt marshes are important buffers for coastal communities and often provide better protection than hard structures like jetties and bulkheads. They also trap sediment, stabilizing shorelines and preventing erosion of inland areas.
• Tidal salt marshes are historically and culturally important; for instance, in the United States, salt marshes are sacred to the Gullah-Geechee Nation, who continue to protect them. In Canada, the marshes of the Queen Maud Gulf (Ahiak) Migratory Bird Sanctuary are significant to the Inuit people.
• Sea-level rise threatens salt marshes everywhere, and some marshes are already deteriorating. Salt marshes rise a few millimeters each year as they accumulate organic matter, but if they cannot keep pace with sea level, they become tidal mud flats. Marshes may adapt by moving inland, but coastal squeeze, in which uplands are too steep or too built up, prevents this for many marshes.
• Invasive species disrupt the interspecies relationships that make marsh ecosystems resilient; they can even hasten the erosion of marshes.
• Urbanization of coastal areas—where most humans live—threatens marshes in many ways. Pollution and sediment may drain into marshes from waterways; “reclamation” may bury them under housing, commercial areas, or even landfills; and mosquito control may be achieved in ways that damage marshes.
• Roadways, levees, dams, tidal gates, and ditches can change the hydrology of the tides that wash salt marshes twice a day, flooding some areas and drying others. Without the tides, salt marshes may become methane producers.
• Agricultural practices can also harm marshes. Ponding or impounding marshes makes them carbon sources, damages nearby marshes, and increases pollution.

Visit a tidal salt marsh. Salt marshes are sanctuaries for abundant and varied birds, safe and fun places for kayaking or canoeing, and beautiful scenes for photography, sketching, or painting.

• Give your enjoyment of the marsh a chance to ripple out. Bring a friend so they can see how beautiful and important these places are. Share your experiences on social media so appreciation of salt marshes spreads. And support local businesses near salt marshes so their communities gain from ecotourism and have even more reason to value and protect marshes.
• Enjoy salt marshes responsibly. If you fish, obey fishing regulations, and don’t take more than is allowed and you can use. Recreational fishing can strip enough top predators from salt marshes to disrupt the balance of the salt marsh ecosystem to the point that the system dies. Off-road vehicle use—even mountain bikes—can leave wheel ruts that last for years, as can off-trail hiking.

Connect with organizations that are protecting and restoring salt marshes. Organizations large and small are involved in salt marsh restoration and protection, and they can be a great way to connect with your community. Volunteer with them, donate, and/or sign up for their newsletters to learn more. See Key Players for several organizations, or search for salt marsh conservation or restoration projects in your area.

• Find tidal salt marshes of international importance at the Ramsar Sites Information List. You can search for marshes in your country or worldwide, see pictures of them, read a short description, and learn more about who manages them.
• Participate in the International Coastal Cleanup, also known as Coastal Cleanup Day. Every September, people around the world participate in this effort to clean up litter on the coast or on waterways that lead to the ocean. Plastics leach chemicals that harm fish and are especially important to clean up.
• Be part of salt marsh restoration work. Restoration can be very effective in expanding marsh habitat rapidly, as in this 15,000-acre project in the San Francisco Bay, and volunteers are often needed for planting and monitoring. Restored marshes begin sequestering carbon almost immediately, as well as providing other ecosystem services like storm buffering and nurturing biodiversity.
• Be a citizen scientist. Citizen scientists have been important contributors to tidal salt marsh monitoring. The World Wetlands Survey needs citizen scientists every few years to assess the health of their wetlands around the world. If you are a birder, join eBird to record your sightings and contribute to data about salt marsh biodiversity. In England and Wales, you can use The Salt Marsh App to investigate and estimate stored carbon in UK salt marshes. In the U.S., there are many examples of citizen science programs in marshes and other wetlands. In Australia, citizen scientists are critical to assessing salt marshes in Tasmania.

Make choices that support salt marshes. Even if you live far from the coast, you can do simple things that help salt marshes thrive.

• Buy sustainable seafood. Shellfish and crustaceans like shrimp, prawns, crabs, mussels, clams, and oysters are often fished in and near salt marshes, and how they are fished can make the difference between a sustainable ecosystem and ecosystem destruction. Monterey Bay Aquarium’s Seafood Watch tools can help you decide which products to buy.
• Prevent waterway pollution. Many waterways drain to salt marshes on their way to the sea. Things as simple as picking up pet waste, minimizing fertilizer and pesticide use, picking up litter when you find it, and disposing of your own trash properly all help keep waterways clean and marshes healthy.

Advocate for and fund salt marsh restoration and protection. Directed funding and legislative change are critical to ensuring the future of salt marshes.

• Start a campaign for community awareness of marsh importance. For example, a “marshie”—salt marsh selfie—campaign in Georgia promoted the need for buffers next to marshes.
• Organize with neighbors to improve your local salt marsh. In Boston, the Mill Creek Salt Marsh Restoration Project restored a half acre of salt marsh and created new recreational opportunities.
• Write to your national or state legislators to request or support legislation and funding for marsh preservation and restoration. If you live in a coastal area, contact your local government to discuss the benefits of marshes and the need to include them in planning and funding. In Montenegro, sustained and savvy pressure on the government saved a salt marsh considered the “Heathrow Airport for migratory birds.”
• Buy a fishing license, fishing stamp, or duck stamp even if you do not fish or hunt. These licenses and stamps help fund research and conservation efforts at the state and federal levels. The duck stamp also provides free access to U.S. federal wildlife refuges, like a park pass for birders.

Prevent eutrophication and pesticide pollution runoff that can affect salt marshes. Excess nitrogen from fertilizer runoff can travel down waterways for miles, ending up in salt marshes. The runoff stimulates microbes in salt marshes to release CO₂ and reduces root growth in marsh plants, making marshes more vulnerable to erosion. By reducing or eliminating fertilizer use, improving soil health, and planting buffer zones like hedgerows or prairie strips, farmers can support marsh health.

• The Regenerative Agriculture Nexus page provides a suite of practices that can reduce costs and improve soil fertility while converting farmland from carbon source to carbon sink.
• Hedgerows (planted with trees, shrubs, and perennials) and prairie strips (planted with prairie grassland species) are inexpensive and effective ways to prevent runoff and provide additional benefits such as bird habitat, pollinator habitat, weed control, and erosion control.

Manage livestock so as to protect salt marshes. Prevent livestock access to salt marsh or use best practices for grazing to ensure the salt marsh stays intact.

• Use rotational grazing if necessary and avoid grazing in marshes especially affected by sea-level rise.
• Do not dam tidal marshes to create ponded pastures, which emit high amounts of greenhouse gases: methane if wet and nitrous oxide if dry.

Prioritize preserving existing salt marshes. Although restoring salt marshes is effective and necessary, restored marshes may take a hundred years to be functionally equivalent to existing salt marshes. The New South Wales government has created this summary of salt marsh management needs.

• Zone and regulate development so salt marshes are preserved. Careful, strict zoning, without variances, is essential to preventing development that endangers marshes. These developments can block marshes from responding to sea-level rise and reduce biodiversity. Requiring generous setbacks and substantial buffers also helps protect marshes and allows them to migrate.
• Protect marshes and nearby land in perpetuity through conservation easements. Conservation easements are voluntary legal agreements that limit uses for a given piece of land in perpetuity. They can be a low-cost way to preserve marshes and allow them to migrate as the sea level rises.
• Plan roadways and causeways so as to maintain tidal flow and not impound salt marshes. Existing roadways and railways have impounded large tracts of salt marsh, cutting them off from the source of their tides.
• Use living shorelines to stabilize and protect coastlines. Living shorelines are shore protection structures made of natural or living materials like vegetation buffers or oyster reefs. They grow over time instead of eroding, provide green space, allow natural marsh function, and support wildlife. They are inexpensive compared to hard shorelines, provide better protection, and are less likely to be damaged during storms. NOAA provides tools for planning living shorelines and an interactive map of example projects.

Restore salt marshes, beginning with returning appropriate flows. At Port Susan in Washington, a collaboration removed a saltwater dike, allowing the marshland to regain eight inches of elevation in seven years and store carbon faster than neighboring marshes. In Essex in the UK, a combination of breaching seawalls and using coir rolls to trap sediment improved flood protection and prevented marsh erosion. Case studies for several sites on the East Coast of the U.S. and in Canada can inform restoration.

• Restore healthy hydrology to marshes. Careful consideration of local hydrology is essential for successful restoration. For marshes where flows have been blocked or reduced, breaching or removing berms, dikes, dams, and tidal gates and enlarging culverts or deepening channels are ways to return flows. Where sea-level rise is creating erosion of salt marsh, ditching can drain water enough to allow recovery.
• Use best practices for other marsh improvements, such as raising drowning marshes with thin-layer deposition and planting native vegetation.
• Consider positive interactions among different species. For example, mussels stabilize and fertilize soil, which benefits cordgrass, a primary foundation species. Scientists found that cordgrass co-transplanted with mussels had three times the survival rate of cordgrass that was transplanted without mussels.
• Ensure local participation in restoration plans. Stakeholders often have different priorities and may be skeptical, but engaging them leads to successful projects, as in the Medmerry project: extensive stakeholder consultation managed local fears of flooding and economic damage, leading to breaching a three-kilometer-long shingle bank that was costly to maintain and no longer effective for flood protection. The breach restored flows to 183 hectares of tidal marshes, flood protection was improved, and a nature preserve became a new attraction for visitors.

Use best practices for integrated mosquito management. Many wetlands do not produce significant numbers of mosquitos, but where they do, surveillance can establish whether local species carry disease, and risk should be assessed. Alteration of hydrology, if it is done at all, should be done with care for the impacts that it has on the rest of the ecosystem.

• Techniques such as runneling or Open Marsh Water Management can minimize the negative effects of mosquito management.
• Maintaining tidal flows can actually improve mosquito management by reducing standing water, while insectivorous bats can provide mosquito control.

Create conservation easements to protect marshes on your land. These easements are legal agreements that stay with the land and protect it for future generations. The Land Trust Alliance can help you understand conservation easements and find a land trust to work with to make sure that agreement is kept.

Make your home salt-marsh friendly. Taking care of your land in ways that protect salt marshes can protect your land as well, while increasing biodiversity.

• Build living shorelines instead of bulkheads to protect property next to marshlands. You may be able to install a simple living shoreline—such as vegetation, bio-logs, or even an oyster reef—yourself. Within a couple of years, a strip of marsh can outperform a bulkhead while improving wildlife habitat: a marsh strip won’t increase erosion of neighboring land and is less likely to be damaged in heavy storms. Be sure to check regulations and permits first.
• Maintain or plant a vegetated buffer strip next to marshland. Using existing and native vegetation and planting on contour lines can create buffer strips that reduce runoff, minimize erosion, provide both privacy and good views, and improve wildlife habitat. They can also save money on maintenance. Local natural resource agencies such as NRCS can help you plan for wetland preservation. In California, you can find a native plant palette for your area.
• Use good garden techniques: Don’t dispose of garden debris close to the marsh, and minimize fertilizer use. Get your soil tested to see what kind of fertilizer you need or whether you even need it.

Teach about salt marshes. Educators have a key role in eliminating one of the main obstacles to salt marsh preservation: lack of understanding. Other habitats, such as beaches, are prioritized in policy and funding, while marshes are overlooked. Education is key to helping children and their families recognize how important salt marshes are and how much they need protection. Like other wetlands, salt marshes are excellent places for environmental education, with many ways to engage (See Environmental Education Nexus).

• NOAA’s estuary curriculum site has curricula from both coasts, such as this lesson exploring the estuary and climate change connection for grades 6-12. 
• Australia has a Wetlands education toolkit, and schoolchildren have been involved in citizen science in Tasmanian salt marshes.

Conduct research on salt marshes. More research on salt marshes and blue carbon generally is needed. Salt marshes are relatively understudied, and basic questions remain unanswered:

• The extent of salt marshes worldwide. In some areas, such as North America, Australia, and South Africa, salt marshes are well-mapped. But in South America and Russia, the location and area of salt marshes are poorly understood.
• Depth of carbon sequestration. An initial study estimated carbon sequestration in soil down to half a meter, but salt marshes that have been in place over millennia may sequester carbon several meters deep. 
• Economic research is necessary to understand the drivers of habitat loss across different locales and improve cost-benefit analysis. Because salt marshes are flat areas in coastal regions, it is important to quantify the opportunity cost of not developing, but a better understanding of economic benefits beyond carbon sequestration, such as flood protection, fisheries, and ecotourism, can drive better decisions on marsh protection.
• Soil organic carbon (SOC) in salt marshes is just beginning to be understood. Questions remain on what affects rates of carbon sequestration, how much that changes when salt marshes are converted to other uses, and how climate change is likely to affect it. We also need improved estimates of SOC and standardized methods for measuring SOC.
• Supportive conditions and best practices for successful restoration of salt marshes.

Partner with nonprofit conservation organizations to aid their work in salt marsh protection and restoration at the local or regional level. Many salt marsh protection organizations, such as the Chesapeake Bay Foundation or CoastCare, partner with businesses for event sponsorships, volunteerism, and investments or grants. Organizations such as Blue Ventures work with local partners to rebuild fisheries and create thriving economies.

Invest in blue infrastructure and blue carbon. There are multiple ways that corporations can invest in conservation. Maryland is working out a framework that allows investment in projects that reduce the administrative burden of conservation work and allows loans for well-defined “blue infrastructure,” including salt marsh projects.

Getting to Know a Tidal Salt Marsh by Deestuary (7 mins.)

It's An Atlantic Sand Fiddler Crab! (2 mins.) See Chesapeake Bay Program for more information. 

Voices of the Great Marsh by Eight Towns and the Great Marsh (15 mins.)

Can South Carolina's Salt Marshes Be Saved? by NOVA / PBS (8 mins.)

Blue Carbon—A Story from the Snohomish Estuary by EarthCorps (6 mins.)

Secret World of Saltmarshes by Gardening Australia / ABC (6 mins.)

Researchers Rush to Protect the UK's Salt Marshes from Sea Level Rise (5 mins)

Medmerry Managed Realignment Scheme on Vimeo by One Take Productions (UK) (3 mins.)

Saltmarsh Sparrow Chick Narrowly Escapes Death by Nature / PBS (5 mins.)

Manylabs Event—Marine Sequestration: Practice, Policies, and Promise by Manylabs (73 mins.)

Dynamics of the Salt Marsh by Sea Science

"Canada's Swamps Are the Secret Weapon to Fighting Climate Change, Say Experts" by Brandie Weikle / CBC Radio

"Rising Sea Levels Threaten the Lives and Livelihood of Those on a Fragile U.S. Coast" by Barry Gordemer / NPR

“Global Carbon Sequestration in Tidal, Saline Wetland Soils” Gail L. Chmura et al., Global Biogeochemical Cycles / Wiley Online Library

“Tidal Marsh Restoration Could Be a Powerful Tool to Fight Global Warming” by Emma Gildesgame / Yale Environment Review

“To Save salt Marshes, Researchers Deploy a Wide Arsenal of Techniques” by Lisa Golden / Mongabay

Australia's Saltmarshes: A Synopsis to Underpin the Repair and Conservation of Australia's Environmentally, Socially, and Economically Important Bays and Estuaries by NESP Marine Biodiversity Hub

Case Study: Improving Marsh Resilience through the Hurricane Sandy Coastal Resilience Program by National Fish and Wildlife Foundation

Bringing Wetlands to Market by NOAA Ocean Podcast (9 mins.)

Coastal Carbon-Sinks, Mobile Health, and Mileva Marić by Nature Podcast (27 mins.)

Inside a Migratory Bird Sanctuary by Scientific American's National Park Nature Walks Podcast (27 mins.)

Let’s Science That! Salt Marsh Eutrophication & Guar Gum Fertilizer Pellets by Charlize Podcast (4 mins.)

Living Shorelines by Diving Deeper Podcast / NOAA (17 mins.)