Coastal Erosion and Adaptation to Climate Change

Coastal erosion is a critical factor in the vulnerability of small-island developing states to climate hazards. Moreover, rising sea levels from climate change are expected to increase coastal erosion and exacerbate flooding and storm surges. The island of Kosrae in the Federated States of Micronesia suffers from severe coastal erosion and was selected as one of five case studies for a recent report evaluating vulnerability to loss and damage from climate change. Kosrae has a much higher degree of human and economic development than other areas studied, but it is particularly vulnerable because of the erosion issue. The maps and survey analysis aim to increase understanding of the extent of coastal erosion, the interaction of coastal erosion and other naturally existing geographical features such as mangrove vegetation, and the viability of previous adaptation measures in order to improve future measures and enhance the island’s resilience to climate hazards.

The map of Kosrae shows areas of strikingly different vulnerability to loss and damage. The red dots on the map at left correspond to areas that have the most severe coastal erosion and are the most vulnerable. These locations also tend to have less mangrove cover (see map inset lower right). Mangroves provide a natural barrier to storm surge and erosion. They grow in brackish water and their dense root systems protect the shoreline, anchoring the soils. They also thrive in areas with shallow waters and gently rising shorelines, as seen when comparing their distribution to the elevation map in the upper right.

Efforts to mitigate coastal erosion in Kosrae have been undertaken. For example, some sea walls have been built to help hold back storm surges, and mangroves have been planted. But in a survey of households, 92 percent of those who engaged in mitigation efforts found that these were not sufficient to prevent erosion, and that furthermore, these efforts sometimes had adverse side-effects. For example, culturally significant rocks have been used to build sea walls, damaging the cultural heritage of the island. In addition, 40 percent of survey respondents say they did not take any measures to counter coastal erosion, and they do not have the resources to adopt measures such as building a sea wall.
___________________________________________________________________________________________

This blog is part of the Map of the Month blog series produced by the Center for International Earth Science Information Network (CIESIN). The map was made by Dara Mendeloff, CIESIN geographic information specialist, for the report, Evidence from the Frontlines of Climate Change: Loss and Damage to Communities Despite Coping and Adaptation, produced by the United Nations University Institute for Environment and Human Security (UNU-EHS) in collaboration with CIESIN, the International Center for Climate Change and Development, Germanwatch, and Global Research and Reporting (Amsterdam). Blog text was drawn from the report, with input from senior research associate Alex de Sherbinin and geographic information specialist Tricia Chai-Onn.