Great Marsh (Cogswell’s Grant)

The Great Marsh is the largest salt marsh in New England. It makes up 22% of the landmass in Essex.¹ The marsh ecosystem, which includes tidal waterways, wetlands, beaches and barrier islands, is highly dynamic and fluctuates with every tidal cycle. However, the ecosystem is being overwhelmed by a series of interconnected anthropogenic stressors, including runoff from impervious surfaces, pollution from runoff and septic systems, erosion, habitat fragmentation, and development.² The marsh is tightly interwoven with the daily lives of people living across Cape Ann, not only as a scenic backdrop and meaningful cultural landscape but also an economic driver and resilient buffer that acts as a sponge, absorbing storm surges and flooding.³

Cogswell’s Grant, owned by the non-profit organization Historic New England, is a colonial-era working farm that borders the marsh.⁴ The property exemplifies many aspects of Cape Ann’s agricultural heritage, including the mosquito ditches dug into the Great Marsh that are common across the region but increase flooding and threaten the resiliency of the ecosystem in the present day.

In addition to salt marsh hay farming, the clamming industry, which focuses on soft-shell clams (Mya arenaria), is particularly important to the Essex economy (and that of Cape Ann more generally). The clams live in mud flats up to a mile into the ocean, and burrow into the mud at low tide to escape predators before emerging to clean themselves in seawater. Wholesale seafood suppliers, such as the Ipswich Shellfish Group, process the commercially harvested clams. These suppliers are major employers on Cape Ann and hire large numbers of immigrant workers.⁵

The marsh absorbs energy and traps sediment to reduce erosion. It also serves as a nursery for the fish and shellfish species that make up a large part of the local economy.⁶ By 2070, 30% of Essex will be subject to coastal inundation.⁷

As the health of the salt marsh continues to decline, Essex will become more exposed to coastal flooding and erosion during the Great Storm.⁸ The Great Marsh is a critical ecosystem to conserve, though this process will require reconciling historical land uses and development that have weakened its resiliency.