The storm that affected a good part of the coast of Catalonia during last Holy Week is an example of the growing risk of environmental damage and coastal infrastructure damage that may increase due to climate change. The protection of the coastline against this type of storm and many other phenomena is being carried out around the world with very diverse solutions, from coastal defenses known as hard (concrete sea walls, for example) to the restoration of conditions natural (dunes and native vegetation).
An international study led by experts from the University of Tokyo (Japan) has reviewed 304 scientific articles that show the most outstanding experiences in this field and, among its conclusions, warns that the extreme meteorological phenomena that are linked (according to all the studies) to current climate change predict an increase in maintenance problems for infrastructure, buildings and the natural environment in many coastal areas. Responses based exclusively on hard works will be insufficient in many of the affected points, and their combination "with solutions based on nature could, in some contexts, create defenses more capable of adapting to the current reality," indicate the authors of this study. , whose results have been published (April 9) in the journal Nature Communications.
Soft and hybrid measures were found to be more cost-effective than hard measures, and hybrid measures provided the greatest overall hazard reduction in low-risk areas. Although their comparative performance during high-risk extreme events is unclear due to lack of data, these results still support the careful inclusion of nature-based solutions to help protect, support and enrich coastal communities.
Japan's spectacular natural coastline, with iconic views of Mount Fuji, windblown pine trees and rocky beaches, has been captured and admired in paintings and prints for hundreds of years. But today, if you walk along the ocean, it can be difficult to find a stretch that preserves its pristine natural seascape. In the early 1990s, a government survey found that about 40% of the coast had been altered with concrete sea walls, filled harbors, tetrapod piles and more, adding swathes of gray to the blue-green landscape. Expanding coastal cities and towns have grown to house most of the population, so protecting homes and businesses from the dangers of tsunamis, typhoons and rising sea levels has become an increasingly challenging challenge. elderly.
“Seawalls, seawalls, dams and breakwaters, the so-called traditional hard measures, despite being the most popular coastal defenses globally and with a proven track record, face challenges in keeping pace with increasing climate risks,” Lam Thi explained. Mai Huynh, a doctoral student in the sustainability sciences graduate program at the University of Tokyo and lead author of a new study on coastal defenses. “These hard structures are expensive to build and require ongoing upgrades and repairs as sea levels rise and climate hazards become stronger. While they are good at mitigating certain coastal 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 the nature and environment we seek to protect.”
To better understand the performance and benefits of different physical and natural coastal defenses, an international team compared the results of 304 academic studies. Nature-based coastal defenses included: “natural” ecosystems, for example, existing mangroves and coral reefs; “soft” measures, which restore, rehabilitate, reforest or nourish natural ecosystems; and “hybrid” measures that combine nature-based components and hard structures, such as placing concrete breakwaters in front of mangroves.
“By incorporating these natural components, we can create coastal defenses that reduce risk and also offer substantial environmental benefits. “We believe these strategies hold great promise in many parts of the world, but they are also not a “fix-all” solution,” said Professor Alexandros Gasparatos of the Future Initiatives Institute at the University of Tokyo.
The researchers analyzed three key aspects of each type of defense: 1. risk reduction (to what extent the measure could reduce wave height and energy, and influence coastal change); 2. climate change mitigation (including carbon storage and greenhouse gas emissions for nature-based measures); and 3. profitability over a 20-year period.
“Our results indicate that among all coastal defense options in lower risk areas, hybrid measures provide the greatest risk reduction. Hybrid measures can take advantage of the advantages of hard and soft measures. “They provide the immediacy of an engineered barrier while largely maintaining the ecological functionality of a permeable vegetated zone,” Huynh said. “All nature-based solutions have been found to be effective in storing carbon, while both soft and hybrid measures are relatively more profitable than traditional hard measures over a 20-year period, although all have positive economic returns.” .
The data presented in the new study provide "strong evidence" for integrating and improving nature-based components into coastal defenses, but the team recommended doing so with caution, the authors say. “All types of coastal defenses still need to be adequately tested by paired experiments under circumstances of extreme events and high-risk urgency,” says Professor Gasparatos. "Until there are many more such experiments focused on this, we must caution against any universal assumptions about the comparative performance of coastal defense options, whether natural, soft or hybrid measures."
While acknowledging the limits imposed by the lack of available research on extreme and high-risk situations, Huynh and Gasparatos still believe this study supports the idea of investing in nature-based solutions for coastal defense in lower-risk areas. Research like this has important implications for policymakers, coastal planners, and communities seeking to make evidence-based decisions.
"I firmly believe that we need to think more carefully about the design and function of these barriers in this era of accelerating climate change," Huynh said. “Nature-based solutions can not only contribute to risk reduction and climate mitigation in many areas, but can also help reconnect people with nature and support biodiversity. “Greening our coastlines can create spaces that improve quality of life, foster community well-being and inspire environmental stewardship.”
