Since around the 2000s, and especially in Europe and North America, there has been a shift in coastal management towards the use of eco-engineering and nature-based solutions – ways of working with natural ecosystems to address environmental challenges, says Seino. “These approaches integrate natural systems which not only protect against storm surges but also preserve biodiversity,” she says.
In areas where natural ecosystems like dunes and mangroves offer protection, experts frequently recommend nature-based solutions as more sustainable options, according to the IPCC. This chimes with research which shows that nature-focused solutions to societal challenges more widely often provide economic and social benefits.
In the US, the National Oceanic and Atmospheric Administration (Noaa) has similarly encouraged the use of “living shorelines“, an approach that uses “green infrastructure” such as plants and sand rather than concrete or rock to defend coastlines. Research has shown this method is effective at protecting against erosion and storm surges and can even be more resilient than bulkheads in protecting against the effects of hurricanes, while also providing other benefits such as soaking up nutrient pollution and supporting fish habitat.
Amendments to Japan’s Seacoast Law in 1999 aimed to implement more sustainable coastal management and conservation plans, but progress has been slow, says Seino. “Once people see concrete hardening as the answer, it’s difficult to change that mindset.” The BBC contacted Japan’s Ministry of the Environment but received no comment.
As long as the dune is in a healthy state, it will function as a natural seawall – Satoko Seino
Since 2018, Japan’s environment ministry has also been promoting an ecosystem-based disaster risk reduction (Eco-DRR) initiative, an approach to disaster prevention which aims to also build a sustainable, safe and affluent society living in harmony with nature. In a letter to the IUCN on 8 November 2019, the Japanese government said an “eco-friendly” seawall would be built at Katoku beach, covering concrete embankments with sand and plants, presenting the project as a nature-friendly Eco-DRR initiative.
“Nice try, but it doesn’t work like that,” says Wesley Crile, a coastal dune restoration specialist at the University of Hawaii who has led on multiple community-based dune restoration projects on Maui Island in Hawaii.
Maui Island has a similar sand dune system and vegetation, including pandanus trees and morning glories, to Katoku. Crile highlights how the community uses natural processes instead of concrete structures to prevent coastal erosion.
“For example, morning glories, which are present both in Maui and Amami, can trap wind-blown sand with their cup-shaped leaves, gradually building up dunes,” Crile says. If a storm takes some sand from the dune, the dune shape will be affected on the surface, he adds. “But when the storm subsides, the sand process will restart and the dune can be rebuilt with time.” Japan’s Ministry of the Environment did not respond to the BBC’s request for comment.
Seino’s coastal seafloor studies have similarly led her to support a natural dune restoration process at Katoku. Healthy beaches have a “natural ability” to recover, even if they are temporarily eroded, she says.