Quantifying cumulative threats to sandy beach ecosystems: A tool to guide ecosystem-based management beyond coastal reserves
Managing marine ecosystems to promote natural functioning and provide for sustainable use is a necessary complement to formal conservation in protected areas. Because the area for conservation and resources for management are limited, both sites and actions need to be prioritized. Sandy beaches are poorly recognised as ecosystems, and thus are neither well managed nor regularly included in conservation initiatives, and are highly threatened. Therefore, we aim to refine an existing cumulative threat assessment (CTA) for beach ecosystems, the outputs of which can inform prioritization of beaches for conservation in reserves and/or various management objectives beyond reserves. We focus on the latter, using the CTA to derive a decision-support tool that aims to provide for use of sandy shores, whilst ensuring their ecological functioning is not compromised. The CTA depends on expert-based scores of threats to ecosystems; these were determined at the VIth International Sandy Beach Symposium (2012) for a baseline scenario under two criteria: functional impact and recovery time. Application of the CTA and decision-support tool is illustrated using the South African beaches. The baseline threat scores were adapted to suit the local context, and spatial trends in the cumulative impact of 15 threats were quantified. South African beaches are exposed to a broad range of cumulative pressure: overall it is relatively low, except where beaches are associated with areas of intensive coastal development. Based on the degree of permanent modification of the shore, and cumulative impact of all other stressors, the decision-support tool classifies beaches as: social-priority areas; ecological-priority areas; or social-ecological areas, each with specific management objectives.