Severn Estuary

The Severn Estuary is the largest coastal plain estuary in the UK with extensive mudflats and sandflats, rocky shore platforms, shingle and islands. Saltmarsh fringes the coast, backed by grazing marsh with freshwater and occasional brackish ditches.

The following mind map illustrates the dynamics of this type of cultural management system.

The estuary's classic funnel shape, unique in the UK, is a factor causing the Severn to have the second highest tidal range in the world (after the Bay of Fundy in Canada) at more than 12 meters. This tidal regime results in plant and animal communities typical of the extreme physical conditions of strong flows, mobile sediments, changing salinity, high turbidity and heavy scouring. The resultant low diversity invertebrate communities, that frequently include populations of ragworms, lugworms and other invertebrates in high densities, form an important food source for passage and wintering birds. The site is important in the spring and autumn migration periods for waders moving along the west coast of Europe, as well as in winter for large numbers of waterbirds including swans, geese, ducks and waders. These bird populations are regarded as internationally important.

As with many other estuaries in England and Wales, the Severn Estuary has long provided a focus for human activity, a location for settlement, a source of food, water and raw materials and a focus for trade and exploration. The Estuary and its coastal hinterland support major cities including Cardiff, Bristol, Newport and Gloucester. The Severn Estuary ports are very important to the regional and, in some cases, national economy. The Estuary's beaches and undeveloped coastline, with low-lying levels, freshwater wetlands, and cliff scenery, provide an important focus for recreation and appreciation of the Estuary's wildlife.

The Severn Estuary is one of 10 RAMSAR sites in Wales which makes Wales a good model with which to make international comparisons between management interactions between cultural and ecology. This comparison is taken up in a comparison of the cultural ecology of Wales and Kenya in the AJUST wiki.

Severnside Levels (lowland wet grassland)

Lowland wet grassland is managed grassland situated below 200m in altitude which may be subject to periodic flooding. It includes flood plain grasslands, man-made washlands, coastal grazing marsh as well as isolated areas of poorly drained grassland However, it does not include salt-marsh.

Sympathetically managed lowland wet grassland is now a scarce and precious resource. There are estimated to be about 1.2 million ha of potential lowland wet grassland in England, Wales and Scotland but according to a survey (Smith 1983) only 7 per cent of the proportion of this potential area falling within England and Wales supports any breeding waders at all.

It has been estimated that 80 per cent of lowland wet grassland in Essex has been lost since 1930 and 50 per cent of the North Kent Marshes (Ekins 1990). The primary threats to lowland wet grassland are: agricultural intensification, land drainage and inappropriate management of existing drainage or flood defence infrastructure.

Threats of lesser importance to lowland wet grassland but which can have significant effects upon those few and smaller sites where they occur are: groundwater abstraction, pollution of groundwater and surface water from acid deposition and neglect in the form of a decline in traditional management.
A number of bird species of conservation concern are dependent or partly dependent on lowland wet grasslands in the UK. Using a wider definition.