Climate change: Impact on coral reef coasts

Abstract

A case study conducted in the Seychelles is described, in which it was estimated that the demise of the shallow corals has and will result in an approximate doubling of wave energy striking the previously protected shorelines. This has resulted in substantial erosion with a high cost to the local population. There are many anecdotal stories of shoreline erosion from around the world, especially around atolls. It is likely that a proportion of them are exaggerated or that the observations made are merely reflecting seasonal changes; it is well known that sandy shorelines behind coral reefs can change by tens of meters or even more on a seasonal basis. However, it is usually not too difficult to distinguish between seasonal changes and unidirectional or progressive changes that have progressed for several years, if only because the latter soon begins to show erosion of previously stable and long-lived shoreline vegetation (Figure 6), and then erosion of built infrastructure. Nevertheless the poor signal-to-noise ratio in matters of shoreline movement is a serious problem, making it difficult, in some cases, to distinguish between the seasonal and storm-driven noise in the system and any underlying, serious progressive trend that may be occurring. What is clear is that all forms of coral damage, whether from local, direct impacts, or from climate change, will reduce the effectiveness of the breakwater effect provided by living coral reefs. Furthermore, in some cases, changes seen to date will be very much less than those predicted for the near future if temperatures continue to rise and if polluting discharges and mechanical extraction continue to reduce the abundance and resilience of coral reefs that fringe shorelines.