A recent study has shown that combining traditional hard coastal defenses like concrete sea walls with nature-based solutions can create more adaptable and cost-effective defenses in some contexts. The study reviewed 304 academic articles on the performance of coastal defenses around the world, including natural environments, soft measures, hard measures, and hybrids of the aforementioned. Soft and hybrid measures were found to be more cost-effective than hard measures, with hybrid measures providing the highest hazard reduction in low-risk areas. While the comparative performance of these measures during extreme events that pose a high risk is unclear due to lack of data, the results support the careful inclusion of nature-based solutions to protect, support, and enrich coastal communities.
In Japan, the dramatic natural coastline has been altered over the years with concrete sea walls, filled harbors, and other hard coastal defenses. With increasing climate risks such as tsunamis, typhoon swells, and sea-level rise, the challenge of protecting homes and businesses in coastal cities and towns has become more difficult. Traditional hard measures, such as sea walls, are facing challenges to keep pace with these increasing risks due to their expensive construction, need for continuous upgrades, disruption to coastal communities, adverse environmental effects, and alteration of the seascape. This has led researchers to explore the benefits of nature-based coastal defenses as alternatives.
An international team compared the results of 304 academic studies to better understand the performance and benefits of different hard and nature-based coastal defenses. Nature-based coastal defenses included natural ecosystems, soft measures, and hybrid measures that combine nature-based components with hard structures. By incorporating natural components into coastal defenses, the researchers found that it is possible to reduce risk and provide substantial environmental benefits. However, they caution that nature-based solutions are not a one-size-fits-all solution and must be carefully integrated into coastal defense strategies.
The researchers analyzed three key aspects of each type of defense: risk reduction, climate change mitigation, and cost-effectiveness over a 20-year period. Hybrid measures were found to provide the highest risk reduction in lower-risk areas, as they combine the advantages of both hard and soft measures. Nature-based solutions were effective in storing carbon, while both soft and hybrid measures were relatively more cost-effective than traditional hard measures over a 20-year period. These findings support the integration and upscaling of nature-based components into coastal defenses but caution against universal assumptions about the comparative performance of different defense options.
While acknowledging the limitations of available research on extreme and high-risk situations, the researchers believe that investing in nature-based solutions for coastal defense in lower-risk areas is a promising approach. They emphasize the importance of conducting more experiments to test the performance of different types of coastal defenses in extreme events and high-risk scenarios. This study has important implications for policymakers, coastal planners, and communities looking to make evidence-based decisions about coastal defense strategies. By greening coastlines and integrating nature-based solutions, it is possible to reduce risk, mitigate climate change, reconnect people with nature, support biodiversity, enhance quality of life, foster community well-being, and inspire environmental stewardship.
