• 1.
    It is hypothesized that the recent intensification of agricultural practice in the coastal fringe of West Connemara, Ireland, has affected the vegetation of vulnerable ecosystems like lakes and wetlands.
  • 2.
    Lakes and wetlands, arranged in three transects running inland from the coast, were studied to detect an assumed decrease in the effects of eutrophication as a result of a decrease in the intensity in land use.
  • 3.
    The data obtained from the vegetation survey in 1988 were compared with those collected at the same sites in 1975. The data were subjected to various multivariate statistics to detect changes in species composition and relationships between these changes and environmental variables such as pH and orthophosphate concentration in the surface waters.
  • 4.
    Changes in species composition are accompanied by changes in environmental factors; notably a marked increase in orthophosphate level indicating an anthropogenic origin for most of the observed changes in vegetation.
  • 5.
    Changes in species composition have also been used to construct a transition matrix for sites between 1975 and 1988. This has served as a basis for a prognosis on the state of the vegetation at these sites circa 2000. Data have also been grouped to indicate lake-specific patterns in the changes.
  • 6.
    The dynamics of all plant species have been established based on their frequency of disappearance from sites since 1975 and their rate of establishment in new sites in 1988. Special attention has been given to species from the red data list. It is concluded that over the past 13 years species diversity decreased in the whole area, and especially in coastal lakes. Red data list species appeared to be the more vulnerable ones.