Wetland habitats

Saltmarshes

Part land, part water, saltmarshes offer a unique landscape that’s home to plants and animals specially adapted for these salt-rich lands.

Soak up the breathtaking beauty of saltmarshes, their never-ending horizons teeming with wildlife.

As the tide ebbs back to the sea and the water retreats across the saltmarsh, it reveals a mosaic of greens and blues. Twisting tidal creeks shelter eels and other fish. The water winding its way through the marshy, low-lying landscape forms pools and flows around the marshland. Here, salt tolerant plants like samphire and sea purslane grow and as the land becomes drier, clumps of purple sea aster and sea lavender flourish. This is the world of Dickens’s ‘Great Expectations.’

‘Ours was the marsh country, down by the river, within, as the river wound, twenty miles of the sea.’

Charles Dickens’s 1861 novel ‘Great Expectations’.

Introduction to Saltmarshes

What are saltmarshes and where can you find them?

Saltmarshes are coastal wetlands that are flooded and drained by the tides. They’re boggy and marshy as their soils are composed of deep mud and peat. They’re found in most parts of the world where there’s low-lying land and a temperate climate. In the tropics and sub tropics they’re replaced by mangroves which are dominated by salt-tolerant trees rather than low growing plants. They can be natural or created.

A created saltmarsh at WWT Steart Marshes. it’s estimated that around 19,000 tonnes of organic carbon has been buried in the first four years since its creation in 2014.

How do they form?

Saltmarshes form in sheltered places along the coast, particularly in estuaries like the Thames, The Wash, Solway Firth and Severn Estuary. They’re created when mud and silt are deposited along a sheltered part of the coastline. Small plants known as ‘pioneer’ species take root, followed by larger plants and organisms. These in turn trap more sediment and as the saltmarsh builds up, more plants become established in the wetland. Because each plant has its own level of tolerance to water and tidal flooding, a saltmarsh can support a variety of plants.

What lives there?

Saltmarshes provide nurseries for fish, as well as a refuge for mammals and birds. Glassworts and cordgrass plants can quickly appear on new saltmarsh and are followed by a succession of other plant species. These plants are useful as they increase the amount of sediment that is deposited on the land, provide food for fish, and slow the movement of water back into the ocean.

Glasswort plants help increase the amount of carbon ‘locked in’ to a saltmarsh

Saltmarshes are important for both resident and migratory birds like egrets, dunlin and spoonbills who use the high grasses as cover in which to raise their young and the mudflats as sources of fish, molluscs and insects. Long-billed wading birds have specially adapted bills with ends that can flex and probe the mud, using masses of mini sensors to pick up pressure waves from bivalves and molluscs.

A dunlin in breeding plumage

And it’s not just birds. Some invertebrates are adapted to feed on just one kind of saltmarsh plant such as the sea aster mining bee, a late emerging bee that times its flight with the blooming of this plant in East Anglia and the Thames estuary.

In the first four years since WWT Steart Marshes was created in 2014, it’s estimated it’s buried 35,000 tonnes of blue carbon as well as providing flood protection for local communities.

Saltmarshes in our culture and history

A foraging feast

People have been finding food on saltmarshes for thousands of years. Many of the best edible plants grow close to the coast and none more so than saltmarsh plants. The most famous of these is marsh samphire. The traditional name for this group of plants was ‘glasswort’ because long before people started eating them, they were burned to extract the silicates from them, which were then used to make glass.

Sea purslane is another popular edible plant. It’s naturally very salty and tender and best served raw as a garnish for fish dishes. Sea beet or sea spinach is the wild ancestor of beetroot, sugarbeet and chard and can be used much as you would normal spinach.

Restoring 22,000 hectares of saltmarsh, as planned, would store at least an additional 88,000 tonnes of carbon dioxide per year.

Why we need saltmarshes

Saltmarshes are one of our most effective weapons in the fight against climate change. They act as giant carbon sinks can be very efficient at locking away carbon.

So how do they do this? Every day on saltmarshes, carbon in the form of sediment is brought in on the tide. When it’s buried in the wet mud, decomposition is slowed down, and the carbon gets locked in. In addition, when saltmarsh plants die, rather than decomposing and releasing their carbon into the atmosphere, the plants become buried in the mud. As sea levels rise, more sediment layers get buried and more ‘blue carbon’ gets locked beneath the mud.

Saltmarshes also perform a vital role protecting our shorelines and the people that live there from flooding. During heavy storms or high tides, they provide a buffer, reducing the strength of the incoming water and preventing the worst of the storm hitting populated areas further inland.

Saltmarshes such as these on the Severn Estuary provide a buffer against storms.

Saltmarshes also act like giant sponges, absorbing and cleaning run-off from farms, filtering out herbicides, pesticides and heavy metals, as well as excess sediments and nutrients.

Scientists at Durham University warn that rising sea levels mean the UK could lose all its saltmarshes by 2100 and they could disappear completely from south east England by 2040.

Saltmarshes under threat

As long ago as the Romans, our desire for more and more ‘productive’ farmland has seen saltmarshes being drained and ‘reclaimed’ from the sea. More recently we’ve drained them to expand our cities and build new airports.

Saltmarshes and the wildlife that live there are also threatened by climate change. Globally, rising sea levels and increasingly frequent and damaging storms are putting them under pressure.

What is WWT doing to protect saltmarshes?

Despite this, there is some good news. Unlike rainforests, which can take centuries to recover, saltmarshes can reform and start providing valuable habitats within a matter of years.

One such example is WWT Steart Marshes in West Somerset, one of the largest wetland creation projects in the UK, restored by WWT and the Environment agency as part of an ambitious project to harness the power of saltmarshes. The aim was to recreate natural wetland features that would protect the area against flooding, restore biodiversity, provide a place for people to enjoy nature and mitigate for climate change. The area has already attracted otters, egrets, owls and spoonbills, as well as providing grazing for locally produced saltmarsh lamb and beef.

WWT creates, protects and restores wetlands for wildlife and people, including saltmarshes, at our sites across the UK and internationally.

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