Southern African sandy coasts in the context of near-future sea-level rise

Abstract

Sandy shorelines occupy ca. 80% of the coast of Mozambique, South Africa and Namibia. A geomorphological classification of sandy shorelines in the subcontinent identifies twelve major categories in four sub-regional coastal systems. The behaviour of each of the major shoreline types under rising sea level is outlined based on geological principles together with observations of former shorelines preserved onshore and on the continental shelf. Human adaptation strategies regarding shoreline change involve a binary choice (hold the shoreline in place or permit it to fluctuate) and these exert an equally important control on sandy shoreline response in the medium term as does sea-level rise itself. It is anticipated that densely urbanised sandy shorelines will be stabilised by coastal defences involving both capital works and ongoing maintenance that will be accompanied by deterioration and ultimate loss/replacement of the natural ecosystem. In contrast, currently undeveloped, natural shorelines will be permitted to adjust and will, as a consequence, survive and continue to deliver ecosystem services. The major challenge for climate-change adaptation lies in those lightly urbanised coastal areas where relatively small numbers of property owners may be, or perceive themselves to be, at risk of economic loss from shoreline change. In such cases the choice is between preserving those property interests (through sea defences) and preserving the sandy shoreline and its human and ecosystem services (via retreat).