Coastal impact ranking of small islands for conservation, restoration and tourism development: A case study of The Bahamas

摘要

An 11-year project to characterize, then assess, the health of coastal environments of The Bahamas ranked a total of 238 sites on ten different islands. Satellite images and aerial photography were used to characterize coastal types (e.g. substrate, geomorphology and wave energy to describe beaches, mangroves, or rocky shores), and then field assessments ranked four types of anthropogenic impacts that influence ecosystem function and coastal system services. The ranking of coastal health was based on physical alterations, destructive use of the coastal zone, coastal development and occurrence of Invasive Alien Species (IAS). The characterization and assessment methods were developed to serve as a rapid survey of coastal stability, biological diversity and quality of wildlife habitats. A system of coastal ranking is presented using numerical scores for four impact criteria along with terrestrial plant surveys to examine the intactness of the coastal environment. Some locations (Exuma and Great Guana Cay) were repeatedly monitored over time. Scores ranged from "0" for no human impacts or invasive coastal plants to "20" for highly altered with dredging, coastal development and loss of native vegetation. The mean impact rank for all sites across all islands was 5.7 ± 4.3, which indicates "Medium" ranks for at least two of the four human impact criteria. Only one uninhabited island (Cay Sal) had all coastal impacts scores of "None". Over 77% of all the sites surveyed had abundant occurrences of Invasive Alien Species (IAS) coastal plants. The Australian Pine (Casuarina equisetifolia) was the more pervasive and the most widespread IAS in the coastal environment, and its abundance increased in all sites that were re-surveyed over time. Degradation of coastal function can signal greater risks to coastal property, flooding events or loss of wildlife populations. The coastal impact ranking protocol presented here helps identify target areas for conservation as well as identify areas with the greatest feasibility for coastal restoration.