Sandy shores of the near future

INTRODUCTION Most sandy shores consist of coupled surf zone, intertidal beach and dune systems (Short & Hesp 1982), which together constitute a littoral active zone of sand transport. Many of these systems were formed during Holocene deglaciation which increased sediment discharge to the shore. This also drove a rapid rise in global sea level to approximately its present elevation by c.5000 years before present (Bird 1993). On open coasts subject to oceanic swell, waterborne sediment transport may extend well beyond the surf zone to a depth of up to 20 m, while aeolian transport of sand extends landward to fully vegetated dunes. In low-energy and estuarine sandy-shore systems both the magnitude and cross-shore extent of transport are smaller. Transport both along and across the shore is critical to the maintenance of the sand budget and consequently to the landforms and habitat on which sandy-shore organisms depend (Clark 1983). Human activities interfere with these sediment exchanges and directly alter, restrict or replace landforms and biota. Global climate change adds further stresses by accelerating rates of change in natural processes and generating human actions to resist these changes. Brown and McLachlan (2002) provided the basis and background for assessment of the future of sandy shores, concentrating attention on subaerial beaches on wave-dominated open coasts. This chapter synthesizes this information with evaluations of coastal dunes, low-energy beaches and human-restored environments, documenting trends and identifying implications for the future.