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Sunday, August 6, 2017

Ninigret Pond at ground zero

Changing Climate Is Impacting Rhode Island’s Fragile Ecosystems

By Alex Burrows and Tanner Steeves in RIDEM’s Wild Rhode Island
Photo by Will Collette

The Ninigret section of Charlestown is well known to Rhode Islanders and visitors as one of the most beautiful natural heritage sites in the state. 

The forested trails, grassland, coastal pond and salt marshes host a wide variety of wildlife and marine species which make it a unique and beloved natural space. 

Unfortunately, the Ninigret salt marsh and salt marshes all along the East Coast are being threatened and degraded. Increases in global temperature are causing sea levels to rise at an accelerated rate, and as a result, Rhode Island’s fragile yet essential habitats are disappearing. 

A loss of salt marsh habitat will have long term effects on Rhode Island’s fisheries, wildlife, coasts and people. 

Salt marshes are unique coastal habitats that develop along sheltered coastlines within intertidal zones and between terrestrial and aquatic habitat, and they are vital to both humans and wildlife. 

These unique ecosystems provide crucial habitat to multiple species of birds, fish, invertebrates, and many other organisms. 

Vegetation becomes established as sediment accumulates in inter-tidal areas. Over time, roots from the vegetation become entangled and form a thick mat, which helps to hold the marsh together and prevent erosion.

These ecosystems are typically distinguished into two areas as low marsh and high marsh habitat. Low marsh habitat is almost always inundated at high tide, while high marsh habitat is less frequently flooded, usually by the highest tide. 

This results in differing levels of salinity, moisture content, and soil composition. 

These factors determine what types of vegetation will grow in specific areas; grasses are more common in low marsh areas while high marsh habitat tends to consist of more low-growing shrubs. 

The vegetation within salt marshes provides critical nesting habitat for birds like the salt marsh sparrow (Ammodramus caudacutus), seaside sparrow (Ammodramus maritimus), and willet (Tringa semipalmata). 

Salt marshes are also beneficial to humans as they protect coastlines from erosion, and filter sediment from the water as the tide ebbs and flows. 

Sea level rise, as a result of climate change, threatens the persistence of salt marshes. Low and high marsh habitat become inundated by seawater, causing a change in the composition of the marsh by increasing salinity and moisture and decreasing oxygen in certain areas, and ultimately degrading the habitat. 

As the mean high tide line creeps further inland, salt marshes are unable to migrate at a similar rate, resulting in significant habitat loss. 

Projections show that sea levels in the northeastern United States are expected to rise several feet by 2100 (NOAA); even a small proportion of this estimate will have grave consequences to Rhode Island salt marshes. 

This change will affect coastal communities by reducing salt marshes’ capability to act as a buffer from storms, protect shorelines, and serve as a natural filter. 

Nesting habitat for birds that rely on these ecosystems would also be eliminated, and the populations of many other species of flora and fauna would be reduced. 

It is important that we take steps to preserve these delicate ecosystems not only for their aesthetic value, but for the crucial role they play in the well-being of our communities and the longevity of wildlife populations. 

RIDEM and other conservation organizations are working proactively to enhance and sustain these critical habitats. 

At Ninigret Pond, a large area of salt marsh owned by RIDEM is undergoing an extensive restoration to adapt the salt marsh to higher water levels by the Coastal Resources Management Council (CRMC) and Save The Bay. 

A technique called thin layer deposition was completed in early 2017, wherein dredged material removed from the Charlestown breachway was spread across the marsh surface to raise the elevation of the marsh by approximately one foot across nearly 20 acres. 

Vegetation will naturally recolonize the site, and thousands of seedlings were planted to help facilitate the revegetation process. 

Small channels known as runnels were also installed to improve tidal flushing and help drain fresh water that had become impounded at upper sections of the high marsh. 

This innovative project will improve the Ninigret salt marsh and help future attempts at salt marsh adaptation as conservationists work to help these ecosystems persist before they are permanently lost.