Sand dunes are not just found in deserts, but they also occur along coastlines worldwide. Coastal sand dunes serve as an important buffer for communities threatened by sea level rise, storms, and coastal erosion. Plants act as magnets for wind-blown sand, anchoring the grains to the developing dune and helping to build resilience against the forces of nature. This environment encourages the opening of ecological space in urban areas, promoting biodiversity of both plant and animal species.
The Problem
More than 45% of southern California’s coastline is groomed with machinery used to remove debris from sandy beaches, creating a flat topography ideal for recreational activities of the local population and tourists. However, vegetation is actively discouraged from growing, reducing habitats for local wildlife and resulting in some native and threatened species becoming locally extinct.
The Solution
Researchers at the University of California’s Marine Science Institute and their collaborators selected a 12,000 m2 site on Santa Monica Beach, Los Angeles, in December 2016 and monitored restoration of the area over six years. This research was designed to test a more sustainable and cost-effective approach to coastal resilience compared to traditional defense barriers.
The restoration project ceased intensive grooming and nourishment of the beach by bringing sediment from other localities to make it larger. Instead, fencing was erected on three sides to trap sand with an opening to the ocean, and seeds of native dune plants were planted. The dune was then monitored for sand accretion and biological activity in the form of plant development and wildlife introductions.
The Results
Within one month of erecting the fences, the researchers measured the beginning of sand being accreted and dune formation (eventually reaching 15 cm in six months), and plants began to germinate within two months. By August 2021, the volume of sand had increased an astonishing 30 m3 per meter of shoreline.
Over the six-year period, they found that approximately 1,730 m3 of sand had accreted onto the site, with the dune elevating 1 m, compared to the uniform size and flatness of the groomed control site 100 m south. While this mechanical activity prevented the establishment of plants on the control beach, the researchers found that over the same period, 7% of the restoration site was covered in vegetation, with some species having developed into specific zones despite being initially evenly spread, and will continue to grow as the years pass.
Within eight months of the project’s initiation, dune beetles made the site their home, having not been observed there prior to the restoration activities, nor in the control site. Significantly, they discovered that an endangered bird species, Charadrius nivosus nivosus (western snowy plover), was breeding in the restorative dunes, its first sighting in the area in over a decade.
The Conclusion
The project highlights the potential for dune initiation to dramatically alter the local landscape over time, with minimal human intervention required thereafter. Similar projects have also been conducted in the Gulf of Mexico, New York, New Jersey, and the Pacific Northwest, offering hope for scaling up passive restoration strategies to mitigate against some of climate’s greatest challenges and open ecological space for the benefit of nature. Coastal sand dunes trap sediment, encouraging expansion instead of erosion, while plants can act as magnets for wind-blown sand, anchoring the grains to the developing dune and helping to build resilience against the forces of nature. This nature-based approach may help urban coastal erosion, offering a more sustainable and cost-effective approach to coastal resilience compared to traditional defense barriers.
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