Assessing atoll island physical robustness: Application to Rangiroa Atoll, French Polynesia

Abstract

This article proposes a comprehensive methodology considering geomorphic, ecological and human variables to assess atoll island physical robustness in the face of climate-ocean pressures. Six variables are considered, including island size, elevation, shape, structure, vegetation and the influence of human activities on island natural capacity to adjust to climate-ocean changes. Each of these variables is ranked on a five-level scale and the rankings are summed up to provide a final estimate in the form of an index of the relative physical robustness of each island. This methodology is applied to twelve islands of Rangiroa Atoll, French Polynesia, considered key to the maintenance of the habitability of the atoll by the local community and exhibiting contrasting physical configurations. The findings emphasize highly contrasting levels of island physical robustness, with indices ranging from 0.33 to 0.75. The main contributors to differences in island physical robustness are, in order of importance, island size and the influence of human activities on island capacity to adjust to climate-ocean changes; island elevation; island shape, structure and vegetation. Some peripheral rural islands that are targeted by the public authorities for future development have a much higher physical robustness than the settled islands. Based on these findings, we advocate, first, for the inclusion of ecological and human variables in assessments of atoll island physical robustness and modelling studies; and second, for within-atoll relocation of people and human assets to more robust island areas and islands.