The vulnerability of South African estuaries to climate change: A review and synthesis

Abstract

This review evaluates the vulnerability of South African estuaries to Climate Change in a data-limited environment. The regional-scale assessment is based on physical characteristics and predicted/measured changes in the abiotic drivers and ecosystem responses. The major Climate Change stressors were identified in order of importance as change in climatic and hydrological processes, ocean circulation and temperature regimes, sea level rise, increase in frequency and intensity of sea storms, and ocean acidification. Flow-related ecosystem responses included changes in mouth state, salinity regimes, biochemical regimes (nutrient fluxes), and floods and related sediment deposition/erosion cycles. The regional vulnerability assessment provides a summary of the key shifts scaled as high, medium, and low in estuary state. Changes in oceanic processes and temperature regimes drive shifts in nearshore temperatures of the transitional zones, with related ecological responses (e.g., range expansion). However, most structural and functional changes are expected along cool temperate and subtropical biogeographical regions, leading to notable shifts in mouth closures and salinity regimes, which in turn will affect estuary function and estuary-associated species. Monitoring and management of resources (e.g., fresh water and fisheries allocations) need to consider this in long-term planning.