natural environments, soft measures (which support or enrich nature), hard measures (such as concrete sea walls), and hybrids of the aforementioned. Soft and hybrid measures have been found to be more economical than hard measures, with hybrid measures offering the greatest hazard reduction in low-risk areas. While their performance in high-risk extreme events is uncertain due to data limitations, these findings still advocate for the thoughtful integration of nature-based solutions to safeguard and enhance coastal communities.
Japan’s striking natural coastline, with its iconic views of the ocean and rugged terrain, has long been a source of inspiration and wonder.The beauty of Mount Fuji, with its wind-blown pines and rocky beaches, has been depicted in paintings and prints for centuries. However, if you take a walk by the ocean today, it can be difficult to find a stretch that still maintains its natural seascape. A government survey in the early 1990s revealed that approximately 40% of the coast had been modified with concrete sea walls, filled harbors, and stacks of tetrapods, adding patches of gray to the blue-green landscape. As coastal cities and towns continue to expand to accommodate the majority of the population, the need to protect homes and businesses from tsunamis, typhoon swells, and rising sea levels has become increasingly important.
“The traditional hard measures like sea walls, dikes, dams, and breakwaters are popular coastal defenses, but they are struggling to keep up with the growing climate risks,” said Lam Thi Mai Huynh, a doctoral student in sustainability science at the University of Tokyo. “These structures are costly to construct and need ongoing maintenance as sea levels rise and climate hazards worsen. While they are effective in mitigating some coastal threats, they are facing an ever-increasing challenge.”tal disaster risks, they can also cause significant disruption to coastal communities and have adverse environmental effects. Furthermore, they often significantly alter the seascape and sometimes alienate local communities from nature and the very environment we seek to protect.”
To gain a better understanding of the effectiveness and advantages of various hard and nature-based coastal defenses, a group of international researchers analyzed the findings of 304 academic studies. Nature-based coastal defenses encompassed “natural” ecosystems, such as mangroves and coral reefs; as well as “soft” measures, which involve restoring, rehabilitating, reforesting, or nourishing natural ecosystems.The researchers studied different types of coastal defense measures, including nature-based options like mangroves and hybrid measures that combine natural and hard structures like concrete breakwaters in front of mangroves. Professor Alexandros Gasparatos from the University of Tokyo’s Institute for Future Initiatives stated that incorporating natural components into coastal defenses can reduce risk and provide environmental benefits. However, he also noted that these strategies are not a universal solution. The researchers evaluated each defense measure based on its risk reduction capabilities and its environmental and social impacts.Coastal defense options in lower-risk areas are evaluated based on three primary factors: 1. risk reduction (including the ability to reduce wave height and energy, and influence shoreline change); 2. climate change mitigation (including carbon storage and greenhouse gas emissions for nature-based measures); and 3. cost-effectiveness over a 20-year period.
According to the findings, hybrid measures are identified as the most effective coastal defense option in lower-risk areas. These measures combine the advantages of both hard and soft measures, providing the immediate protection of an engineered barrier while preserving the ecological functionality of a permeable vegetated zone,” said Huynh. The study also concludes that all nature-based solutions are effective in reducing risk.In terms of carbon storage, soft and hybrid coastal defense measures are more cost-effective than traditional hard measures over a 20-year period, and all have positive economic returns,” the study concluded. The team recommended integrating and scaling up nature-based components into coastal defenses, but cautioned that further testing is needed. “All types of coastal defenses have not been thoroughly tested in extreme event scenarios, so we must be cautious about making universal assumptions about their effectiveness,” Gasparatos warned. “More experiments focusing on this are necessary before making any final conclusions.
Coastal defense options, including natural, soft, or hybrid measures, were evaluated in a study on their performance. Huynh and Gasparatos noted the limitations of available research on extreme and high-risk situations but still argue that investing in nature-based solutions for coastal defense in lower-risk areas is a worthwhile idea. This research has significant implications for policymakers, coastal planners, and communities seeking to make informed decisions.
According to Huynh, “In this era of rapidly accelerating climate change, we need to carefully consider the design and function of these barriers.”
Huynh stated that nature-based solutions not only help with risk reduction and climate mitigation, but also with reconnecting people with nature and supporting biodiversity. Greening coastlines can create spaces that improve quality of life, promote community well-being, and encourage environmental stewardship. The journal reference for this statement is: Lam Thi Mai Huynh, Jie Su, Quanli Wang, Lindsay C. Stringer, Adam D. Switzer, Alexandros Gasparatos. Meta-analysis indicates better climate adaptation and mitigation performance of hybrid engineering-natural coastal def.The article in Nature Communications published in 2024 discusses the effectiveness of new mosquito repellent measures. The DOI for the article is 10.1038/s41467-024-46970-w.