The diversity of landforms existing along the coastline offers many unique habitats for different marine plants and animals.

With a length of around 8,000 km18, England’s coastline is a wonderfully diverse and constantly changing national asset: from the predominantly hard rocky coasts of the south west and north east, to the softer mudflats, saltmarsh and estuaries of East Anglia or the Irish Sea. Much of our soft coastline is dynamic (or should be), either in the short term or over longer timescales. Soft coastlines range from easily eroded mudstone cliffs of Dorset, through the chalk of Kent and Sussex, to extensive areas of salt marsh, sand dunes, shingle or sandy beaches and some of the most environmentally important estuaries in Europe. Variations in the geology, wave exposure and tidal currents, along with the change in climate from south
to north, all interact to produce a varied mosaic of habitats, supporting a wide diversity of important wildlife. Understanding the process of continuous change is essential if we are to work with nature to achieve sustainable coastal management. The erosion of soft cliffs and longshore sediment transport provides material to develop saltmarshes, sandy beaches or sand dunes.
These provide a natural coastal defence with benefits for biodiversity and people. The impacts of planning and coastal management decisions, combined with a lack of understanding of, or reference to the geomorphological dynamics of our coastal systems and habitats, are a major reason why our coastal ecosystems are not in good enough condition. We review the state of each of our coastal habitats in the following sections.

Rocky Tide Pools

Along a rocky coastline, pools of water can be trapped in depressions of the rock as the tide recedes. Although called tide pools, these tiny reservoirs of water are also fed by rain and by spray from nearby breaking waves. The pools contain many forms, and colors, of algae, but the most common is a type of brown algae called rockweed. These algae are known as seaweed. A variety of small animals, including barnacles, mussels, starfish, and hermit crabs, make their home in and around the pools. To keep themselves from being washed into the sea by strong waves or tidal currents, barnacles and mussels cling to the rocky surface. Barnacles cement themselves directly to the rock. Mussels attach themselves by sticky threads that can be pulled back and reformed, allowing a mussel to change its position when necessary.

Sandy Beaches

At first glance beaches appear barren, but in fact many organisms make a home there. Beach sediments are continually flushed by the swash water, which carries oxygen and bits of animal and plant debris into the pore spaces between the sand grains. This action creates an ideal environment for microscopic organisms, including fungi, algae, bacteria, and protozoa. This same region is occupied by burrowing animals such as clams and worms. These animals bury themselves in the sand to avoid detection by predators and to escape the strong wave motions. Clams feed by extending a pair of tubes, called siphons, through the sand and into the overlying water. Water is drawn in through one tube and expelled through the other, creating a feeding current. The feeding current passes through a series of gills, which filter out the bits of plant and animal debris that are used for food. Marine animals feeding in this manner are known as filter feeders. Clams migrate with the tide to maintain the best possible feeding position and to avoid being eaten by birds.

Tidal Flats

Tidal flats are divided into regions based on elevation and how long a particular region is underwater. The low tidal flat is closest to the sea and is submerged for most of the tidal cycle. Deposition rates are low in this region because it is continually exposed to tidal currents, so sediment grains are kept in motion and prevented from settling to the bottom. Moving inland, the mid-tidal flat is submerged for roughly half of the tidal cycle. Both the low tidal flat and the mid-tidal flat are inhabited by filter feeders, such as clams. The abundance of these organisms attracts large flocks of wading birds and gulls, which can feed on as many as 30 to 50 clams per hour.
The high tidal flat, farthest from the sea, is submerged only during high tide, a time when tidal currents are weak and deposition is rapid. These conditions cause sediment to accumulate rapidly. As the level of the high tidal flat rises, its time underwater declines. Eventually the high tidal flat is dry for sufficiently long periods for land plants, typically marsh grasses, to grow, and a salt marsh forms. Continued deposition causes the salt marsh to expand seaward. Channels cut throughout the marsh continue to bring seawater into and out of the older, landward parts.

Mangals

In tropical regions, tidal flats are dominated by trees and shrubs called mangroves, instead of by marsh grasses. A community of mangroves is called a mangal. Unlike most trees and shrubs, a mangrove's root system is largely above ground. The above-ground roots enable the plant to breathe; roots below ground in a tidal flat cannot breathe because the soil is waterlogged. In addition, mangroves are unusual trees because they can grow in regions of salty water.
The mesh of mangrove roots dampens the flow of water, producing a quiet marine region that is well suited for young organisms. For this reason, several fish species lay their eggs in mangals. In addition, mangals provide permanent homes for many animals, including birds, frogs, snakes, and crocodiles. Burrowing crabs, mud lobsters, snails, and shrimp use the muddy bottom as their home.
Mangals are threatened by nature, in the form of destructive tropical storms, and by human activities such as dredging and water pollution. Restoration efforts, to counter the human threats, aim at preserving the ability of mangals to protect shorelines by stabilizing sediment and damping wave action.

Estuaries

The region of coast where the fresh water of a river meets the salty water of the ocean is called an estuary. An estuary includes many different habitats and thus harbors many different plant and animal species. The shoreward end of an estuary often includes a tidal flat or a mangal. Regions of strong current or waves attract filter feeders, such as oysters, clams, and mussels. Shallow regions, where currents and waves are weak and where light can reach the bottom, abound with submerged meadows of sea grass. These more sheltered regions are home to deposit-feeding animals, such as the mud snail or mud crab, which feed on plant and animal debris buried in the mud. Moving inland, the salinity decreases and the vegetation at the estuary border shifts from salt-resistant sea grasses and marsh grasses to freshwater marsh grasses and forest.
An estuary is a region of relative shelter, so many ocean fish use it as a nursery. Flounder, for example, lay their eggs amidst the sea grass. The eggs have an adhesive covering that allows them to cling to the vegetation. The young fish spend several months in the estuary before moving to the open ocean.
As estuaries become more polluted, the deposit feeders and filter feeders are at risk because the food they eat tends to accumulate chemical pollution. These poisons will accumulate in their bodies and be passed on to shore birds, animals, and humans that eat them. In addition, pollution tends to reduce the amount of light that can penetrate the water. This reduction in light decreases the growth of aquatic plants and limits sea grass to shallower regions, diminishing an important habitat for many species.

Coral Reefs

Coral reefs are an unusual coastal feature because they are built not from sand or rock but from living organisms. A coral reef is made of the skeletons of coral animals, as well as other marine invertebrates (animals lacking a backbone) such as algae and sponges. Coral requires sunlight for growth, so only the uppermost portion of a reef is alive. The base of a reef consists of the dead remains of previous generations. A reef grows upward slowly as new organisms build atop the remains of dead ones. If sea level rises, the community can adapt by growing upward more rapidly, allowing the living surface of the reef to remain close to the water surface.
Coral reefs are remarkably productive ecosystems. They have been compared to tropical rain forests for their great biodiversity. It is estimated that half a million species of plants and animals live in coral reefs. Scientists estimate that one half of all coral species are still unidentified.
Coral are sensitive to changes in their environment. They thrive only in clear, warm, nutrient-poor, shallow water where wave action is not so strong as to rip the reef apart yet strong enough to stir the water and deliver sufficient food and oxygen. Coral reefs are threatened by several human activities. Silt, caused by erosion from land development, can bury coral or make the water murky, both of which block the sunlight necessary for coral growth. Excess nutrients, caused by agricultural runoff or the dumping of sewage, foster the growth of plants or blooms of plankton, which also block sunlight from reaching the coral. Heavy fishing alters the fragile balance of animal life within the coral reef system. Divers damage coral by breaking off pieces to be sold as souvenirs.