Why salt marshes and seagrass meadows matter

Canada’s extensive coastline is replete with natural wonders, from the rugged rocky shorelines and fjords in Newfoundland and Labrador to glass sponge reefs in B.C. to the extensive kelp forests found along all three coasts. 

But between land and sea is an often-overlooked habitat: coastal wetlands — beautiful and complex ecosystems that provide invaluable benefits to wildlife, climate and people.  

What exactly are coastal wetlands, and why are they so important? In the first of a four-part series, we’ll shallow dive into those benefits — what we in conservation call “ecosystem services” — by way of their unsung heroes: salt marshes and seagrass meadows. 

Protective powerhouses

So, what are they? We might think about salt marshes and seagrass meadows as the fabric of coastal ecosystems; through them weave water, nutrients, native species, cultural practices and more.

Salt marshes are a type of wetland that is regularly flooded and drained by the tides. Salt-marsh plants, such as rushes, grasses and sedges, have adapted to withstand the ebb and flow of coastal conditions: large fluctuations in water, salt content, temperature and oxygen levels. Seagrasses, on the other hand, are aquatic flowering plants that can form extensive meadows in the brackish and calm coastal waters of shallow inlets, bays and estuaries. These meadows grow very fast and are the main food source for many species. (In Canada, the main seagrass species is eelgrass).

Both salt marsh plants and seagrasses are incredibly effective at absorbing carbon from the atmosphere, storing it in their roots and shoots and, eventually, into the underlying sediment where it can remain for thousands of years. In fact, these tidal ecosystems are so effective that this stored carbon gets its own category: blue carbon. In Canada, coastal wetlands sequester more carbon per square metre than terrestrial forests, making them important allies in the fight against climate. 

In addition to this unique carbon-storing capacity, salt marshes and seagrass meadows also fight climate change impacts. Their dense root systems help stabilize sediment and reduce wave energy, preventing shoreline erosion and protecting coastal communities from climate-fuelled storm surges and flooding, making them increasingly invaluable assets as sea levels rise. 

From hatching to harvest, a biodiverse balance

Salt marshes and eelgrass meadows are also rich biodiversity hotspots, supporting a wide array of plant and animal species. 

They provide feeding and breeding grounds for numerous fish, shellfish, migratory birds and other wildlife. Salmon, for example, seek food and protection in eelgrass during their early stages of life. And they’re not the only ones — studies have shown that over 80 per cent of commercial fish and shellfish species in the Pacific Northwest are estimated to depend on eelgrass habitat at some point in their lifecycle.

While some species are visitors to coastal wetlands, others spend their entire lives within these habitats. The Maritime ringlet, for example, depends on two salt marsh species: sea lavender and saltmeadow cordgrass. The entire global range of this small butterfly is restricted to the coastal salt marshes surrounding the Baie des Chaleurs, between Quebec and New Brunswick.  

Food security and cultural values

Coastal communities have deep cultural connections to these ecosystems, relying on them for recreation, traditional harvest, gathering and spiritual practices. 

Preserving these ecosystems therefore not only conserves biodiversity but also maintains cultural heritage and fosters community well-being, as is the case with traditional shellfish harvest, which provides food but also an opportunity for local and Indigenous intergenerational learning and connection to the land. 

The salt marshes of the Bras d’Or Lake/Pitu’pok in Nova Scotia are critical habitat for the American eel. The eel is a food source for the Mi’kmaq and plays an important role in cultural and ceremonial practices. The Mi’kmaq also harvest sweetgrass from salt marshes for medicinal purposes. Glasswort (also known as pickle weed, sea asparagus or samphire greens) is harvested from salt marshes all over the world. And eelgrass is a traditional food source for some coastal First Nations, including the Haida, Nuu-chah-nulth and Kwakwaka’wakw Peoples.

Nature’s filtration system

Runoff from hard surfaces like concrete, asphalt and rooftops is a leading cause of water pollution (oil and other chemicals from vehicles, pet waste, detergents, etc.) while agricultural operations contribute extra nutrients, pesticides and silt to local waterways. Salt marshes and eelgrass meadows effectively trap sediments and absorb excess nutrients, improving water quality in estuaries, bays and nearshore waters. By acting as natural filtration systems, they help mitigate the effects of nutrient pollution, supporting the health of coastal waters and fisheries. 

It is vital that we recognize the critical role of coastal wetlands and make concerted efforts to protect, restore and steward them, especially as pressures from coastal development, pollution, invasive species and climate change continue escalating. In the second part of this series, we’ll take a closer look at what exactly those biggest threats are, and why coastal ecosystems are uniquely vulnerable to them. Stay tuned!