SALT MARSHES

With wide open views, natural beauty, and diverse wildlife, salt marshes are one of the most productive ecosystems on the planet. Their grasses, flooded and drained by tides, accumulate captured sediment and decomposing plant matter to form peat and provide growing space for roots, allowing marsh to rise and keep pace with sea levels.

Marshes are divided into two distinct zones, with a minor difference in elevation: low marsh, which floods daily at high tide, and the predominant high marsh, known for fine low grasses that flood only a few times each month. These wetland areas are especially vulnerable to projected climate change effects due to a legacy of widespread ditches and tidal restrictions that disrupt natural water flow.

Climate Change Impacts

The Great Marsh, the largest salt marsh in New England at more than 20,000 acres, is considered one of the East Coast’s most resilient marsh systems. Yet our latest data shows potentially dramatic shifts by 2070. Nearly 14,000 acres could flood daily, compared to 1,500 now, with at least 400 acres of Great Marsh completely lost [CIT. 2]. Impacts include:

• Sea Level Rise Outpacing Marsh Accretion Without intervention, high marsh is likely to convert to low marsh, tidal flats, or be completely submerged [CIT. 2].

• Weakened Marsh Shoreline Resistance to waves, possibly causing erosion and endangering homes, businesses, and roads.

• Loss of Refuge, Feeding, and Breeding Areas, posing risks to fish, shellfish, plants, and migratory birds such as the salt- marsh sparrow, whose population is declining by 9% per
  year [CIT. 12].

• Loss of a Natural Climate Solution Coastal ecosystems such as salt marshes improve water quality and absorb carbon at rates up to 50 times greater than forests.

• Loss of Recreational and Economic Activities such as bird watching, fishing, shellfishing, boating, and hiking. The shellfish harvest in Great Marsh communities alone was valued at more than $5 million in 2018 [CIT. 8].

Current Coastal Strategies

It’s not too late to save our marshes, large sections of which are owned by conservation nonprofits and public agencies. Ongoing strategies include:

Remediating the Legacy of Ditching With few exceptions, the marshes throughout Essex County are home to the remnants of ditches once used for increasing agricultural production and controlling mosquitoes. The result was altered hydrology and marsh loss. To reverse this trend and restore marsh health, The Trustees is “healing” old agricultural ditches across more than 300 acres in Newbury, Essex, and Ipswich, by cutting marsh vegetation and securing it in low ditches to trap tidal sediment, allowing peat to rebuild.

Reducing the Impact of Aged Aquatic Barriers The Ipswich River Watershed Association is working with communities to reduce the impact of aquatic barriers such as dams, culverts, and bridges on natural salt tidal flow.

Creating Living Shorelines Salem, among other places, is restoring fringing salt marsh. The city is using biodegradable coir rolls and salt marsh vegetation to help naturally protect its popular Collins Cove recreational pathway and nearby homes from wave action and flooding.

Protecting Coastal Land Mass Audubon and Greenbelt, Essex County's Land Trust, manage Rough Meadows Wildlife Sanctuary in Rowley on more than 265 acres of salt marsh and adjacent upland once slated for development. The sanctuary protects land suitable for accommodating sea level rise and encompasses coastal woodlands, salt marshes, tidal creeks, and salt pannes with diverse wildlife.

Future Opportunities 

We need cost-effective, marsh-wide restoration projects that sustainably target areas with the best chance of resiliency and ability to adapt. And we need them now since full restoration frequently takes a decade or more. Based on our latest findings, we propose:

Implement Restoration and Resiliency at-Scale Restoring thousands of acres of marsh requires close partnership with communities, land- owners, regulators, and organizations up and down the coast. It means making investments in low-risk, nature-based techniques such as removing tidal restrictions, ditch remediation, and runneling to improve tidal flow and help marsh keep pace with sea level rise.

Rebuild Marshes Through Innovation It’s time to test new approaches such as Mud Motors, which involve strategically placing dredged sediment in tidal channels, so it can naturally, continuously disperse to nearby salt marshes.

Enacting Effective Public Policy State and local wetland laws and regulations must go beyond existing impacts to also consider future resiliency benefits when permitting for actions such as pilot marsh restoration.

Mitigating Development and Conserving Salt Marsh Migration Pathways If new salt marsh is to migrate onto higher ground, land must be permanently and sustainably protected from development. Tools can include coastal buyouts, rolling easements, conservation and deed restrictions, and in-lieu fee programs once we identify what is protected and what is not.