Forested bioshields and tsunami impact mitigation in a Polynesian setting

Abstract

In the 21st century tsunamis have claimed the lives of over 250,000 individuals, and have caused extensive damage to vulnerable coastal ecosystems. This vulnerability continues to increase in many areas as human activity further degrades the coastal forests that once provided a degree of protection against storms and tsunamis, collectively known as high energy marine inundation events. This work presents a case study of the design and implementation of a forested bioshield established to protect a vulnerable wetland on Maui's south east coast. Although subject to coastal inundation, this ecosystem provides high quality habitat for numerous endangered species. Anthropogenic modifications around the wetlands, particularly the loss of the protective forest, have made this ecosystem vulnerable to future inundation events. Establishing an effective bioshield requires in-depth knowledge of both the frequency and intensity of inundation events, as well as effective tree species selection and their proper configuration within the bioshield. Here, we present palynological and archaeobotanical data from the studied wetlands, and combine this with local paleotsunami data, previously published data on forested bioshields, and traditional ecological knowledge to design, optimize and install an 8,000 m² forested bioshield, and review the wider benefits and limitations of this bioshield approach.