Is ecosystem-based coastal defense a realistic alternative? Exploring the evidence

Abstract

Low Elevation Coastal Zones (LECZ) are located at less than 10 m above sea level. Because of human encroachment, combined with sea level rise and increased storminess, LECZ are at an increasing risk of flooding and erosion. In consequence, there is a growing need for shoreline protection. Traditionally, hard infrastructure was used, with positive local results, but negative regional impacts when flows were not maintained. Therefore, ecosystem-based coastal protection has been considered as an alternative. We explored the scientific literature to look for evidence that proves the effectiveness of natural ecosystems for protection against flooding and erosion, when these events are a problem to society. We found that although the protective role of vegetation has been mentioned for over 50 years, most of the studies date from the last decade and have been performed in the USA and the Netherlands. Mangroves, saltmarshes and coastal dunes are the ecosystems most frequently studied. The evidence we found includes anecdotal observations, experimental tests, mathematical analyses, models and projections, economic valuations and field observations. Although mostly effective, there are limitations of an ecosystem-based approach and probably, different strategies can be combined so that protection is improved while additional ecosystem services are maintained. We conclude that, besides improving coastal protection strategies, it is fundamental to reduce human pressure by mobilizing populations inland (or at least promoting new developments further inland), and minimizing the negative impact of human activities. We need to be better prepared to deal with the climate change challenges that will affect LECZ in the not very distant future.