Marsh Landscapes Introduction

Ecosystem Value

Cape Ann’s marshes are critical cultural landscapes. Marsh Landscapes include saltmarsh ecosystems, as well as wetlands, estuaries, and tidal flats.

The largest saltmarsh complexes on Cape Ann are The Great Marsh and the Annisquam River Marsh. There are smaller complexes found bordering beaches and creeks throughout the region. The Great Marsh is the largest saltmarsh in New England. The Marsh stretches over 20,000 acres from Rockport to southern New Hampshire.¹ Since the 1600s, the Annisquam River has served as a navigation and trade route, and its marshes have supported shellfishing beds and fisheries.²

Saltmarshes are transitional zones between upland areas and the ocean. These areas are dominated by tides that flood and drain twice a day. Mixing saltwater from the ocean and freshwater from rivers and streams recharges marshlands with oxygen to support plants and wildlife. These ecosystems sequester carbon at three times the rate of terrestrial ecosystems, both in the soil and in vegetative matter.³ Saltmarshes also play a critical role in buffering storm surges by attenuating wave energy.⁴ During heavy rainfall, they absorb excess water, mitigating flood risk to nearby areas. Additionally, healthy saltmarshes accrete soil and build up sediment over time, adapting to gradual sea-level rise.⁵

Saltmarshes also serve as the base of the marine ecosystem in several ways. The origins of several life cycles begin in marsh habitats as bacteria and fungi are consumed by worms and mollusks and then larger fish. They provide nurseries and feeding grounds.⁶ Atlantic cod (Cadus morhua), Pollock (Pollachius pollachius), Haddock (Melanogrammus aeglefinus), and Striped Bass (Morone saxatilis) are all found in the marshes along the Annisquam River. The marsh is also home to smelt (Osmeridae) and remnant oyster (Ostreoidea) populations, which help filter suspended solids that contain nitrogen and organic compounds from the water, improving the water’s clarity and quality.⁷ Saltmarsh health in Cape Ann is directly tied to marine health.

“I think people don’t realize the habitat value of eelgrass areas. People love to say they are pro-fisheries, but they don’t realize that eelgrass is a nursery for fish.” —Andrew Brouseau, Partner and Compost Manager for Black Earth Compost⁸

The primary shellfish species harvested on Cape Ann are Soft shell (steamer) clams (Mya arenaria), Razor clams (Ensis directus), Blue mussels (Mytilus edulis), Surf clams (Spisula soldissima), Ocean quahog (Artica islandica), quahog (Mercenaria mercenaria), American oysters (Crassotrea virginica), and European oysters (Ostea edulis). Thirty-nine clam beds are in the Annisquam, separated into Upper and Lower Annisquam River areas. High marshes are also home to critical bird species, including Saltmarsh Sparrows, which are obligate species that breed and feed in saltmarsh habitats.

Cape Ann’s saltmarshes are critical wildlife habitats. The dominant species in New England saltmarshes are Smooth cordgrass (Spartina alterniflora) and Saltmarsh hay (Spartina patens). These two species occupy distinct zones in the marsh in relation to tidal datums. Smooth cordgrass dominates low marsh habitats, while Saltmarsh hay grows primarily in high marsh habitats. Black rush (Juncus gerardii) grows at higher elevations, followed by a band of High-tide bush (Iva frutescens).⁹

While Cape Ann’s Marsh Landscapes provide critical ecosystem services, they are not operating optimally. Many of the challenges they face are caused by direct human intervention such as infill, dredging, ditching, and pollution.

Current Challenges

Many of Cape Ann’s estuaries have been degraded over time by fill. Half of tidal saltmarshes have been lost in the United States since the 1900s.¹⁰ This ongoing process is documented in Cape Ann’s historic maps, showing saltmarshes decreasing over time and buildings erected on former marshland.¹¹ Marsh fill displaces water during storm surges and constricts tidal channels, which can exacerbate the duration and depth of flooding. Coastal construction filled large marsh areas during the eighteenth and nineteenth centuries. Smaller filling operations are ongoing, including documented debris and sand dumping in the saltmarshes behind Good Harbor and Wingaersheek Beaches.¹²

Dredging operations across Cape Ann maintain navigable channels of fifteen to twenty feet. While these operations increase human access to marshes, there are several trade offs. Dredging negatively impacts fish eggs, larvae, juveniles, and adults. These operations impair water quality, suspend sediments, and can smother and destroy existing habitat.

Marsh ditching has also caused ecosystem degradation. Ditching has been practiced historically throughout Cape Ann as a part of colonial hay cropping operations and as mosquito control through 1930s New Deal work programs. This process has changed water flow and sedimentation patterns and quickened erosion, increasing the ecosystem’s susceptibility to sea-level rise.¹³

Road construction and upland development directly impact marsh landscapes. Polluted runoff from roadways, sedimentation, and stormwater flows directly into the marsh, impacting critical habitat for fauna, including shellfish. Several clam bed areas are closed seasonally due to water quality issues from three main tributaries to the Annisquam: the Jones River, Cross Creek, and Little River.¹⁴ Clam beds are also closed after rainfall events with one inch or more of rainwater due to stormwater running into the River carrying pollutants and increased nutrient loads from upland areas. In 1980, thirty percent of productive Softshell clam beds were closed due to pollution from coliform bacteria. This was due to sewage dumped in Gloucester Harbor that is pushed up the Annisquam by currents.¹⁵ These beds are the primary habitat for Softshell clams (Mya arenaria), the most important commercial and recreational species.

“Suboptimal function limits the quantity and quality of services an ecosystem can provide. Not only does this obscure the potential ecological and economic value of a given ecosystem, it also reduces the system’s inherent adaptive capacity and resilience when faced with acute stressors or disturbances, such as storms, drought, or disease outbreaks. Limited resilience makes impacted ecosystems more vulnerable to climate change and more likely to cross tipping points that make conservation and/or restoration ecologically, economically, or politically unfeasible.”—Dr. Catherine Matassa, University of Connecticut¹⁶

Additionally, invasive species threaten the ecological health of Cape Ann’s marshes. A grass species, the Common reed (Phragmites australis), has entered areas with reduced salinity, its colonial spreading often outcompetes other species. The European green crab (Carcinus maenas) is also highly invasive. They consume Softshell clam seeds and are highly destructive to saltmarsh. This species is becoming dominant in Gloucester’s estuaries and tidal rivers.¹⁷ Warming trends in the Gulf of Maine have caused marine species to migrate into marsh systems, threatening the ecological balance.¹⁸

“Ten years ago, I would have said the Great Marsh is pretty healthy for the most part . . . Now, in the past five years, I have certainly seen the impacts of sea-level rise coming rapidly. We are getting die-off locations on the marsh from impounded water, some of the pans and pools are getting larger, the vegetation is changing, and there is more erosion along the marsh edge, so a lot of change is happening quickly, and I don’t think I would say it is as healthy as it was ten years ago.” —Peter Phippen, Great Marsh Partnership and Essex Selectmen¹⁹

As tides rise, high marsh is observed to be transitioning to low marsh that is more frequently inundated. These changes will reduce high marsh habitat to just thirty-six acres across all of Gloucester by 2070.²⁰ The eradication of high marsh along the Annisquam will contribute to the extinction of the obligate Saltmarsh Sparrow and harm other wetland-dependent bird species. The lack of ecosystem migration potential perpetuates this conversion process. Shoreline hardening and tidal restrictions created by roads, seawalls, bulkheads, and docks restrict ecological movement, threatening marsh existence within the region.

Future Opportunities

Despite these ongoing challenges, there are multiple opportunities for ecological regeneration through a variety of plans, interventions, and projects. Cape Ann has several interest groups committed to saltmarsh and wetland health and has pursued restoration projects for decades.

There is potential to restore Cape Ann’s marshes and their adaptive capacity to mitigate sea-level rise by filling marsh ditches and removing hydrological barriers.

“A key action throughout Cape Ann’s coastal wetlands would be to restore ditching so that as the sea-level increases, the wetlands have the tools to cope with it by accreting more sediment... As sea-level increases, it could happen that new wetlands appear in previously unoccupied sites. Given their importance, I would support those new wetlands to evolve with no or little intervention.”—Dr. David Moreno-Mateos, Oxford University²¹

Additionally, there is potential to conduct a financial assessment of Cape Ann’s marshes. For example, it is estimated that saltmarshes in New England produce an average annual value of $1,863 per acre for carbon and $2,537 per acre for non-carbon ecosystem services.²²

“Given the limited financial resources available for ecosystem restoration and protection, decision-makers must connect public choices with ecological outcomes regarding ecosystem services. This linkage can be a potent tool for building consensus and support for conservation efforts.” —Dr. Catherine Matassa, University of Connecticut²³

For additional information regarding Cape Ann’s Marsh Landscapes, see the West Annisquam Case Study Dossier.