Comparison of the Physical Susceptibility of Pacific Islands to Risks Potentially Associated with Variability in Weather and Climate

Abstract

This chapter details an objective method of developing an index of island susceptibility to climate change. Three separate indices are developed to estimate the potential of an island to physical change in response to likely climatic changes. These are indicative susceptibility, exposure index and geomorphic susceptibility. To develop the indicative susceptibility, four physical variables that are readily available or can be calculated from other datasets were used. These were lithology, shape of islands, maximum elevation and area. The exposure index took into account broad-scale climate and oceanic processes, such as composite water level range (ENSO and tide), average annual significant wave height and tropical cyclone frequency. The geomorphic index was a combination of the first two with relevant weightings applied. A database encompassing 15 countries and 1532 islands spread across the Pacific Ocean was developed. Analysis showed that there was a wide spread of island susceptibility, with reef islands mostly being very highly susceptible while volcanic high islands were the least susceptible. Some countries in the Pacific had all their islands in the high or very high susceptibility classes, confirming the potential risks climate change poses for them. The index has the potential to be used as a rapid appraisal tool for prioritization of adaptation measures to a changing climate.