Coastal Rewilding & Salt Marshes: Britain's Blue Carbon Frontier

Stand on the edge of a salt marsh at high tide and watch the sea reclaim its ancient territory. Silvery water threads through channels carved over millennia, submerging beds of samphire and sea aster. Waders probe the mud. Somewhere, a curlew calls. This is one of Britain's most productive ecosystems, and one we're only now learning to value.

For centuries, we drained salt marshes for farmland, built sea walls, and turned our backs on the coast. Now, facing rising seas and a climate emergency, we're realising these habitats hold one of the keys to adaptation.

What is Coastal Rewilding?

Coastal rewilding means restoring natural processes to shorelines: allowing salt marshes to form, reconnecting estuaries with their floodplains, and removing or setting back hard defences that have separated land from sea.

Coastal rewilding recognises that fighting the sea is increasingly futile. Instead, working with natural processes creates habitats that provide flood defence, carbon storage, fisheries nurseries, and wildlife corridors—all while adapting to climate change.

The Salt Marsh Ecosystem

Salt marshes are among the harshest environments for plants, flooded twice daily with salt water, baked by sun, scoured by storms. Yet specialised species thrive here, creating one of Britain's most productive habitats.

Zonation

Salt marshes show distinct bands of vegetation based on how often they're flooded:

• Pioneer zone – glasswort (samphire) and cordgrass colonise bare mud
• Lower marsh – sea aster, annual sea-blite, common saltmarsh-grass
• Mid marsh – sea lavender, sea purslane, thrift (sea pink)
• Upper marsh – sea wormwood, red fescue grass, transitioning to dry land

Wildlife

The productivity of salt marshes attracts an abundance of life:

• Wading birds – redshank (the "sentinel of the marsh"), curlew, oystercatcher, dunlin
• Wildfowl – brent goose, wigeon, teal, shelduck graze marsh vegetation in winter
• Fish – bass, mullet, flounder use creeks as nurseries; 60% of commercial species depend on estuaries
• Invertebrates – the nationally scarce fisher spider, various crabs, shrimps, and molluscs
• Plants – specialists like golden samphire, sea heath, and the endangered least lettuce

Ecosystem Services

Blue Carbon & Climate

"Blue carbon" refers to carbon captured and stored by coastal and marine ecosystems. Salt marshes, seagrass beds, and mangroves (in tropical regions) are the planet's most efficient carbon sinks, and restoring them is increasingly recognised as a climate solution.

How It Works

Salt marsh plants capture CO₂ through photosynthesis like all plants. But unlike forests, the carbon doesn't get released when vegetation dies. Instead, it's buried in waterlogged, oxygen-free sediments where decomposition is slow. Over centuries, thick layers of carbon-rich peat build up.

Climate change makes coastal habitats even more valuable. As seas rise, salt marshes can migrate landward if given space, continuously storing carbon while providing natural flood defence. Hard sea walls prevent this migration, causing "coastal squeeze" that destroys marshes from both sides.

Threats to Coastal Habitats

England has lost an estimated 85% of its salt marsh since 1860. The pace of destruction accelerated dramatically in the 20th century, and threats continue today.

Restoration Techniques

Coastal restoration ranges from simple non-intervention to major engineering projects. The approach depends on site conditions, funding, and the balance between nature conservation and existing land uses.

Managed Realignment

The most ambitious technique involves deliberately breaching or removing sea defences to allow tidal flooding of former farmland. This typically follows a careful process:

1. Site assessment – evaluate sediment conditions, tidal range, and ecological potential
2. Landowner engagement – often requires purchasing or compensating agricultural land
3. New defence construction – build a setback defence to protect remaining land
4. Breach creation – carefully controlled breaching of old sea wall
5. Monitoring – track sediment accretion, vegetation colonisation, and wildlife

Regulated Tidal Exchange

Where full realignment isn't possible, controlled structures can allow limited tidal flooding. Sluices, tide gates, or breaches with restricted openings create brackish habitats that benefit wildlife while maintaining some flood protection.

Saltmarsh Restoration

Degraded existing marshes can be restored through:

• Grazing management – light grazing maintains diversity; removing or reducing grazing helps recovery
• Creek restoration – reopening blocked channels improves tidal flushing
• Invasive species control – managing Spartina allows native vegetation to recover
• Sediment recharge – adding dredged material can raise eroding marsh surfaces

UK Restoration Projects

Wallasea Island, Essex

The RSPB's Wild Coast Project transformed 670 hectares of low-lying farmland into one of Europe's largest coastal wetland restoration sites. Using 3 million tonnes of soil excavated from London's Crossrail tunnels, the project created mudflats, salt marsh, saline lagoons, and grazing marsh. It now supports avocets, spoonbills, and marsh harriers.

Steart Marshes, Somerset

The Environment Agency and Wildfowl & Wetlands Trust created 250 hectares of new inter-tidal habitat by breaching sea walls on the Severn Estuary. Completed in 2014, Steart Marshes now hosts thousands of wintering birds and demonstrates how managed realignment can work alongside continuing agriculture.

Medmerry, West Sussex

The largest open coast managed realignment in Europe (2013), Medmerry created 183 hectares of intertidal habitat while providing improved flood protection to over 300 homes. The site is now a nature reserve with significant populations of waders and wildfowl.

Alkborough Flats, Humber Estuary

This managed realignment scheme on the Humber created 440 hectares of inter-tidal habitat in 2006. Studies show it now stores significant flood water during tidal surges, demonstrating the "room for the river" concept that's increasingly applied to coasts.

Cwm Ivy Marsh, Gower

The National Trust is allowing natural coastal processes to reshape this Welsh site, creating a mosaic of salt marsh, dune, and freshwater habitats. It demonstrates how "do nothing" approaches can be as valuable as active intervention.

Visiting Salt Marshes

Salt marshes are accessible year-round, though spring and autumn migrations bring the greatest bird spectacles. Always check tide times, as the character of a marsh transforms completely between high and low water.

Top Salt Marsh Sites

• North Norfolk Coast – Titchwell, Holkham, Blakeney Point, among Britain's finest coastal wetlands
• Morecambe Bay, Lancashire – vast expanse of salt marsh and mudflats, famous for wintering waders
• Dee Estuary, Wales/England – internationally important for wintering birds, accessible reserves at Burton Mere
• Solway Firth, Scotland – wild and remote salt marshes on both Scottish and English shores
• The Wash, Lincolnshire – Britain's largest estuary with extensive salt marsh and mudflats

Visiting Safely

• Check tide times, as incoming tides can cut you off quickly on flat marshes
• Stick to marked paths where possible; soft mud can be treacherous
• Use binoculars to observe birds from a distance to avoid disturbance
• Wear waterproof boots, as salt marsh vegetation often conceals channels
• Never attempt to cross unmarked mud or sand without local knowledge