DILEMMAS IN THE THEORY AND PRACTICE OF BIOLOGICAL CONSERVATION AS EXEMPLIFIED BY BRITISH COASTAL LAGOONS

North Atlantic lagoons contain a number of species and assemblages of organisms not found in adjacent marine, estuarine or freshwater systems, but which do occur in other non-tidal brackish or salt waters, including the abundant brackish ponds and fleets created by man during land reclamation and coastal protection. In order to conserve 'lagoonal organisms' or 'lagoonal communities' it is not, therefore, necessary to conserve lagoons, although North Atlantic lagoons are of highly individual, and rare, physiographic types that are worth conserving in their own right. Most natural lagoons in this region have either evolved into freshwater lakes (themselves evolving into reedswamp) or have been lost through erosion or landward movement of the enclosing barrier. Only the partly artificial, percolation-fed lagoons in reclaimed marshland are likely to escape these fates. Just over half of the remaining British lagoons are within nature reserves or are Sites of Special Scientific Interest, but this protection is largely accidental and in almost no case is the lagoon itself the object of conservation management. Neither are those receiving this gratuitous protection necessarily the best examples of lagoonal systems either physiographically or biologically: half of the ten 'key sites' are not protected whilst several low grade sites are safeguarded. All North Atlantic-indeed all the world-lagoons would be overwhelmed by the rise in sea level considered likely to result from the 'greenhouse effect', although transgression of the sea and barrier materials are likely eventually to form new, and more extensive, lagoonal environments.