Published online by Cambridge University Press: 05 June 2002
Pollution, mining, disruption of sand transport and tourism development widely affect sandy shores, and these systems may be subject to increased erosion in future, yet there have been few attempts to review them. The present review focuses largely on ocean sandy beaches, providing an introduction to much of the relevant literature, and predicting possible states of the system by 2025. Sandy shores are dynamic harsh environments, the action of waves and tides largely determining species diversity, biomass and community structure. There is an interchange of sand, biological matter and other materials between dunes, intertidal beaches and surf zones. Storms and associated erosion present the most substantial universal hazard to the fauna. Human-related perturbations vary from beach to beach; however, structures or activities that impede natural sand transport or alter the sand budget commonly lead to severe erosion, often of a permanent nature. Many beaches also suffer intermittent or chronic pollution, and direct human interference includes off-road vehicles, mining, trampling, bait collecting, beach cleaning and ecotourism. These interferences typically have a negative impact on the system. Identified long-term trends include chronic beach erosion, often largely due to natural causes, as well as increased ultraviolet (UV) radiation and changes related to global warming. It is not expected that predicted temperature changes will have dramatic effects on the world's beaches by 2025, but the expected rise in sea level, if coupled with an increase in the frequency and/or intensity of storms, as predicted for some regions, is likely to lead to escalating erosion and consequent loss of habitat. It is suggested that increased UV radiation is unlikely to have significant effects. Increases in coastal human populations and tourism, thus increasing pressure on the shore, while serious, may be largely offset in developed and developing countries by better management resulting from greater understanding of the factors governing sandy-shore systems and better communication with beach managers and developers. Beach nourishment is likely to become more widely practised. However, the continuing hardening of surfaces in and above the dunes is bound to be damaging. Human pressures in many underdeveloped countries show no signs of being mitigated by conservation measures; it is likely that their sandy shores will continue to deteriorate during the first quarter of this century. A long-term trend that cannot be ignored is the excessive amount of nitrogen entering the sea, particularly affecting beaches in estuaries and sheltered lagoons. The data presently available and the uncertainty of a number of predictions do not permit of quantitative assessment or modelling of the state of the world's sandy shores by the year 2025, but some tentative, qualitative predictions are offered.