A study of the impacts of fragmentation on the North Kent grazing marshes landscape characteristics, features and vegetation communities
Coastal grazing marshes are low lying wet grasslands, which have been reclaimed from tidal saltmarsh. They are drained by a series of ditches and dykes, which together with the grasslands provide a range of fresh and brackish wetland habitats favourable to a wide range of plant, invertebrate, bird and mammal species. As a result of this range, coastal grazing marshes have been recognised as a habitat of major importance within the UK Biodiversity Action Plan. The North Kent Grazing Marshes contain some of the largest remaining areas of coastal grazing marsh in the UK, but in recent years, the North Kent Grazing Marshes have become increasingly fragmented due to the pressure for land for arable production and development. The impacts of fragmentation on the North Kent Marshes have been described as 'death by a thousand cuts', but the impacts of fragmentation processes on coastal grazing marshes have not been previously studied. Despite being highly valued in conservation terms, their importance having been recognised through conservation designations at local, regional, national and international levels; coastal grazing marshes have never been fully defined, either interms of their vegetation communities or their landscape characteristics. This study sought to define coastal grazing marshes in terms of the landscape characteristics and features, and to identify the range of vegetation communities, which are typical of theNorth Kent Marshes. The methodology used both quantitative and qualitative field studies, and was aimed at associating changes to the landscape characteristics and features and the vegetation communities to different fragmentation processes. Historical data (Ordnance Survey and historical maps) were used to determine the pattern of fragmentation of the North Kent Marshes from the end of the nineteenth century to the present day and to identify the fragmentation processes, which were responsible for the breaking up of the marshes. The findings indicate that in most cases grazing marsh fragmentation was initially caused by division by roads or railways, which led to development pressures and fragmentation by intrusion, envelopment or encroachment. Changes to the landscape characteristics and features bought about by fragmentation were shown to be associated to changes in the vegetation communities. Significant correlations were found to exist between the area of a fragment and the status of the landscape characteristics and features and with the type of vegetation community present. The results were discussed in terms of how the fragmentation processes have influenced changes to the landscape characteristics, features and the vegetation communities, and the possible implications of future fragmentation. The ideal grazing marsh was defined in terms of landscape characteristics; features and vegetation communities and monitoring procedures are also proposed.