Atlantic Salt Marshes: Champions for Coastal Animals and Seaside People

A quiet, muddy stretch of coast, dotted with waving grasses and winding tidal creeks. A peaceful picture of a salt marsh, but one that does not tell this habitat’s full story. These often-overlooked ecosystems are powerhouses of natural services.

Image

Alan Clark

Providing a home — essential habitat, food sources and nursery grounds — for many imperiled animals is another piece to the salt marsh’s story. They also, however, work quietly but effectively to clean our water, protect our communities from storms and reduce the impacts of climate change.

A Pollutant Goalie

Salt marshes, like other maritime “forests,” are nature’s Brita filters on a massive scale. As tidal waters flow in and out, they pass through dense grasses, mud and vegetation. This ebb and flow traps and filters pollutants including heavy metals, chemical runoff from farms and roads, microplastics, pesticides, fertilizers, sewage and sediment. This filtration helps protect nearby bays, estuaries and oceans, making water cleaner and healthier for people and wildlife alike.

Image

Jim Moore (CC BY-NC 4.0)

Salt marshes aren’t the only workhorses in this process, though, as oysters and other shellfish help too. A single oyster can clean up to 50 gallons of water a day through filter feeding. They remove sediment, nitrogen and even chemical pollutants. Oyster reefs also create new habitat, while physically trapping sediment that would otherwise cloud the water.

Salt marshes are champions of nutrient cycling, particularly when it comes to two common pollutants from agricultural runoff: nitrogen and phosphorus. Along with nearby seagrasses, salt marshes absorb and recycle these nutrients before they can reach open water. Too much nitrogen or phosphorus can trigger algal blooms, deplete oxygen in the water, and lead to mass die-offs of fish and marine life like Florida manatees. Their role in this cycle is essential to the health of coastal ecosystems and the seafood industries that rely on them.

Image

Jan Reyniers

Storm Defensemen

Human lives and property in the face of hurricanes and tropical storms have always been an ever-present danger in coastal communities. Salt marshes are a first line of defense during coastal storms. Their spongy soils and dense plants absorb wave energy, buffer storm surges and reduce flooding. They act as sinks for rising water, absorbing massive amounts of water during hurricanes. Not only does this all help protect homes and infrastructure near the coast, but salt marshes also shield upland habitats that might otherwise be washed away.  

As sea levels rise, salt marshes can also migrate inland, so long as they are given the space. Marsh migration is the natural, gradual process where sediment builds upland with rising sea levels, allowing marsh-specific types of vegetation to spread. Over time, upland buffer areas become salt marsh themselves. This can help coastlines adapt over time. In this way, marshes offer a natural solution to climate resilience, slowing down floodwaters and reducing erosion.

Image

Graham McGeorge

Red Card for Carbon, Trophy for Salt Marshes

One way to reduce the impacts of greenhouse gases – the leading cause of climate change – is to support “carbon sinks.” Salt marsh habitats are among the most effective natural carbon absorption tools on the planet. They can capture carbon dioxide from the atmosphere up to 10 times faster than mature tropical forests and hold onto much more carbon – known as blue carbon – than they produce.  

Marsh landscapes are dominated by salt-tolerant plants such as cordgrass and sedges. Through the process of photosynthesis, these plants absorb carbon dioxide from the atmosphere and convert it into organic carbon. When plant material dies, it settles into the marsh soil, where waterlogged, low-oxygen conditions significantly slow decomposition. This allows organic matter to accumulate and become buried, forming peat-rich soils that trap carbon for centuries or even millennia.  

Image

A Team Player in Culture and Recreation

Salt marshes are deeply valuable to people and society. Beyond offering protection and the potential for a healthier future, they offer opportunities for recreation and subsistence and have been integral to coastal communities for generations.  

They are more than functional. Salt marshes connect us to nature, support local economies and preserve cultural traditions. But every development that overtakes a marsh, or heavy metal that pollutes them, puts salt marshes and all those who depend on them – people and animals alike – at risk. It’s critical for us to protect and restore Atlantic salt marshes now, so they can continue to thrive for generations to come.

This is the second installment in a short series about Atlantic salt marshes. Read about how they provide a home to many animals in the first story here.