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Unlock This CourseCoastal vegetation plays a crucial role in protecting our shorelines from the powerful forces of waves, wind and storms. Plants act like natural shields, absorbing wave energy and holding soil together with their roots. Understanding how vegetation affects coasts is essential for managing coastal erosion and protecting communities living near the sea.
Key Definitions:
Coastal plants protect shorelines in several ways: their roots bind sediment together, their stems and leaves absorb wave energy and they trap sand and mud to build up the coastline. This natural protection is often more effective and cheaper than artificial sea defences.
Coastal environments are harsh places for plants to live. They must cope with salt spray, strong winds, shifting sands and occasional flooding by seawater. Different plants have evolved special features to survive these challenging conditions.
Sand dunes form when wind blows sand inland from beaches. Pioneer plants like marram grass are the first to colonise these bare sandy areas. These hardy plants have special adaptations that help them survive and gradually stabilise the dunes.
Has deep roots (up to 3m) that bind sand together. Waxy leaves reduce water loss and can roll up in dry conditions. Grows quickly to keep pace with sand accumulation.
Thick, waxy leaves with spines reduce water loss and protect from salt spray. Deep taproot reaches fresh water below the surface. Blue flowers attract pollinators.
Spreads by underground stems (rhizomes) to form dense mats. Narrow leaves reduce surface area for water loss. Can tolerate being buried by sand.
Salt marshes develop in sheltered coastal areas where mud and silt accumulate. These wetland areas are regularly flooded by high tides, creating extremely salty conditions. Plants here must be specially adapted to cope with salt water.
Stores salt in its fleshy stems and leaves. Can excrete excess salt through its surface. Grows in the lowest, saltiest parts of salt marshes.
Has salt glands that excrete salt crystals from its leaves. Purple flowers bloom in late summer. Grows in middle marsh areas.
Thick, fleshy leaves store fresh water. Can filter salt from seawater through its roots. Purple daisy-like flowers attract insects.
Vegetation protects coasts through several important mechanisms. Understanding these processes helps explain why vegetated coastlines are often more stable than bare ones.
When waves hit a vegetated coastline, the plants absorb much of the wave energy. Stems and leaves create friction that slows down the water, reducing its erosive power. Salt marshes can reduce wave energy by up to 70%, making them incredibly effective natural sea defences.
Research shows that 100 metres of salt marsh can reduce wave height by 50%. This is equivalent to a sea wall several metres high, but costs much less to maintain and provides additional benefits like wildlife habitat.
Coastal vegetation acts like a natural filter, trapping sediment carried by waves and tides. Plant stems slow down water flow, causing sand and mud to settle out. Over time, this builds up the coastline and makes it higher and more stable.
Plant roots create a network underground that binds sediment particles together. This makes the coastline much more resistant to erosion. Some plants like marram grass have roots that extend several metres deep.
Human activities can seriously damage coastal vegetation, making coastlines more vulnerable to erosion. Understanding these impacts is crucial for effective coastal management.
Walking, cycling and driving on sand dunes destroys vegetation and creates gaps where wind can blow sand away. Popular beaches often suffer from severe dune erosion due to heavy visitor pressure.
Cars and motorbikes compact sand and destroy plant roots. Creates bare patches that are vulnerable to wind erosion.
Repeated walking creates channels through dunes. These become wind tunnels that accelerate erosion.
Camping on dunes damages vegetation and creates fire risks. Tent pegs and guy ropes disturb root systems.
Building houses, hotels and roads on coastal areas removes vegetation and changes natural drainage patterns. This makes the coastline more vulnerable to storm damage and flooding.
Coastal managers increasingly use vegetation-based approaches to protect coastlines. These 'soft engineering' solutions work with natural processes rather than against them.
Damaged sand dunes can be restored by replanting with native species and controlling human access. This involves collecting seeds from local plants, growing them in nurseries and carefully transplanting them to damaged areas.
The National Trust has successfully restored sand dunes at Formby by planting marram grass and creating boardwalks to reduce trampling. Volunteer groups collect seeds and help with planting. The restored dunes now protect the railway line and nearby towns from coastal flooding.
New salt marshes can be created by allowing seawater to flood low-lying coastal areas. This 'managed retreat' approach gives space for natural coastal processes to operate while providing flood protection for areas further inland.
Involves moving sea defences inland and allowing the sea to flood the area between the old and new defences. This creates new intertidal habitats including salt marshes that provide natural coastal protection.
Using vegetation for coastal protection offers many advantages over traditional hard engineering approaches like sea walls and rock armour.
Vegetation-based defences are much cheaper to install and maintain than concrete sea walls. They also provide economic benefits through tourism, fishing and carbon storage.
Salt marsh creation costs about £500 per metre compared to £5,000 per metre for sea walls.
Healthy vegetation grows and adapts naturally, requiring minimal human intervention.
Provides flood protection, wildlife habitat, recreation opportunities and carbon storage.
The RSPB has created Europe's largest man-made salt marsh at Wallasea Island. Using soil from London's Crossrail project, they built new islands and allowed them to flood with seawater. The resulting salt marshes protect the Essex coast from flooding while providing habitat for thousands of birds. The project cost £50 million but provides flood protection worth £150 million.
While vegetation-based coastal management has many benefits, it also faces some challenges that managers must consider.
Rising sea levels and more frequent storms put pressure on coastal vegetation. Some salt marshes are being 'squeezed' between rising seas and coastal development, leaving no room for them to migrate inland.
Faster sea level rise may outpace the ability of salt marshes to build up through sediment accumulation. This could lead to marsh drowning and loss of coastal protection.
Vegetation-based defences need more space than hard defences. In densely developed coastal areas, there may not be enough room for effective salt marshes or sand dunes.
Coastal managers are developing new approaches that combine vegetation with other techniques to create more resilient coastlines.
These combine natural vegetation with small-scale engineering works. For example, low rock breakwaters can be built offshore to reduce wave energy, allowing salt marshes to establish in their shelter.
Coastal vegetation provides natural, cost-effective protection against erosion and flooding. While human activities can damage these natural defences, careful management and restoration can enhance their protective capabilities. As climate change increases coastal risks, vegetation-based approaches will become increasingly important for sustainable coastal management.