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Unlock This CourseSalt marshes are some of the most productive ecosystems on Earth, yet they're often overlooked. These wetland areas form where land meets the sea, creating a unique environment where only specially adapted plants and animals can survive. Salt marshes act like natural sponges, soaking up storm surges and protecting our coastlines from flooding.
Key Definitions:
Salt marshes develop in sheltered coastal areas where sediment can accumulate. They need protection from strong waves, which is why they form behind barrier islands, in estuaries, or in sheltered bays. Over time, mud and organic matter build up, creating the perfect conditions for salt-tolerant plants to establish.
Salt marshes have several distinctive features that make them unique coastal environments. Understanding these characteristics helps explain why they're so important for both wildlife and coastal protection.
The most important factor shaping salt marshes is the tide. Different areas of the marsh are flooded for different lengths of time, creating distinct zones with their own plant communities.
Closest to the sea, flooded twice daily. Only the most salt-tolerant plants like glasswort can survive here. The mudflats are often bare except for algae.
Flooded at most high tides. Dominated by cord grass (Spartina), which has special adaptations to deal with salt water and waterlogged soils.
Only flooded during spring tides. More diverse plant community including sea lavender, thrift and various grasses. Less salty conditions allow more species to thrive.
The Wash is the largest area of salt marsh in the UK, covering over 33,000 hectares. It demonstrates perfect zonation patterns and supports over 300,000 birds during winter months. The area shows how salt marshes naturally protect the coast - during the 1953 floods, areas behind salt marshes suffered less damage than those with sea walls alone.
Plants living in salt marshes face enormous challenges. They must cope with salt water, waterlogged soils and changing conditions as tides come and go. The plants that thrive here have developed amazing adaptations.
Salt is toxic to most plants, but salt marsh plants have evolved clever ways to handle it. Some exclude salt at their roots, others store it in special cells and some even excrete it through their leaves.
Cord grass (Spartina) has special salt glands on its leaves that excrete excess salt. You can often see salt crystals on the leaf surfaces. Its roots can also exclude salt and it has air spaces (aerenchyma) to transport oxygen to waterlogged roots.
Different salt marsh plants use various survival strategies beyond just dealing with salt.
Plants like glasswort store water in thick, fleshy leaves. This dilutes the salt concentration and provides water reserves during low tide.
Many salt marsh plants have flexible stems that bend with tidal currents rather than breaking. This helps them survive the mechanical stress of moving water.
Some plants develop extensive root systems to anchor themselves in the soft mud and to access fresh water deeper in the soil.
Salt marshes support an incredible variety of animals, from tiny invertebrates to large birds and marine mammals. The rich plant life and regular tidal flooding create perfect feeding and breeding conditions for many species.
The mud and plant material in salt marshes teem with small creatures that form the base of complex food webs. These invertebrates have their own adaptations for salty, waterlogged conditions.
Ragworms, lugworms and cockles burrow in the mud, filtering food from the water or sediment. They can tolerate changing salinity levels and have special gills for underwater breathing. Their burrows also help oxygenate the mud.
Salt marshes are crucial for many bird species, providing food, nesting sites and safe roosting areas during high tide.
Curlews, redshanks and dunlin use their long bills to probe the mud for worms and shellfish. Their legs are adapted for walking in soft mud.
Wigeon graze on salt marsh grasses, while shelducks filter-feed in shallow pools. Many species use salt marshes as winter feeding grounds.
Skylarks and meadow pipits nest in the higher marsh areas, while terns may nest on shell banks within the marsh system.
Salt marshes provide enormous benefits to both wildlife and humans. These 'ecosystem services' are often worth millions of pounds but are frequently taken for granted.
Salt marshes act as natural sea defences, absorbing wave energy and reducing coastal erosion. They're much more effective than hard sea walls at dealing with storms and rising sea levels.
The plants and irregular surface of salt marshes can reduce wave heights by up to 70%. This protects the coastline behind them and reduces the need for expensive sea walls. During storms, they can absorb massive amounts of water.
Salt marshes are incredibly efficient at storing carbon and improving water quality, making them valuable in fighting climate change and pollution.
Salt marshes store carbon in their soils at rates 10 times higher than tropical rainforests. This 'blue carbon' stays locked away for centuries.
The plants and sediments filter pollutants from water, removing excess nutrients that could cause harmful algal blooms in coastal waters.
Salt marshes trap sediment from rivers and the sea, helping to build up the coastline and reduce erosion elsewhere.
Unfortunately, salt marshes are under threat worldwide. In the UK, we've lost over 85% of our salt marshes since Roman times, mainly due to human activities.
Salt marshes face multiple pressures from human activities and climate change. Understanding these threats is crucial for developing effective conservation strategies.
Coastal development for housing, industry and ports has destroyed many salt marshes. Land reclamation for agriculture has also been a major cause of loss, particularly in areas like the Fens and Somerset Levels.
Morecambe Bay contains some of the UK's most important salt marshes, supporting 170,000 wintering birds. However, the area faces challenges from sea level rise, coastal squeeze (where marshes can't migrate inland due to development) and changes in sediment supply. Conservation efforts include managed retreat and salt marsh restoration projects.
Protecting and restoring salt marshes requires a combination of approaches, from legal protection to active management and restoration.
Many UK salt marshes are protected as Sites of Special Scientific Interest (SSSIs) or Special Protection Areas (SPAs) under EU legislation.
Managed realignment projects involve removing sea defences to allow new salt marshes to develop on former agricultural land.
Controlling grazing, managing visitor access and monitoring water quality help maintain healthy salt marsh ecosystems.