The Fringing Reef Coasts of Eastern Africa—Present Processes in Their Long-term Context

Abstract

Sea-level changes through the Quaternary era have provided recurrent opportunities for the biosphere to significantly shape the coastal geomorphology of eastern Africa. Key agents in this shaping have been the calcium carbonate-fixing biota that have constructed the ocean-facing fringing reefs and produced the extensive backreef sediments that form the limestone platforms, cliffs and terraces that characterise these coasts. Today's reefs comprise tough, algal-clad intertidal bars composed largely of coral rubble derived from their ocean front. They provide protection from wave attack to the inshore platforms with their sediment veneers and their beach and beach plain sands that are susceptible to erosion. If the eastern African coasts are subjected to the rise of sea-level that is predicted at the global scale during the coming century, the protective role of the reef bars will be diminished if their upward growth fails to keep pace. Favourable ocean temperatures and restraint in the destructive human pressures impacting the reef ecosystems will facilitate such growth.