Reversing Shoreline Armoring: Quantifying the Effectiveness of Restoration on Coastal Biota of Puget Sound

Abstract

Shoreline armoring is prevalent around the world with unprecedented human population growth and urbanization along coastal habitats. While armoring structures, such as riprap and bulkheads, are built to prevent beach erosion and protect coastal infrastructure from storms and flooding, such structures can deteriorate habitats for migratory fish species, disrupt aquatic-terrestrial connectivity, and reduce overall coastal ecosystem health. One question is whether armoring is reversible, allowing restoration via armoring removal and related actions of sediment nourishment and replanting of native riparian vegetation. Relative to armored shorelines, natural shorelines retain valuable habitats for macroinvertebrates and other coastal biota. Remarkably, few assessments of the responses of coastal biota to shoreline-armoring removal exist. Here, I use pre- and post-restoration data for five biotic measures (wrack % cover, saltmarsh % cover, number of logs, macroinvertebrate counts and richness) from a set of restored shorelines in Puget Sound, WA, USA. I find that a broad suite of ecosystem metrics responds strongly and positively, and that these results are evident after less than a year. Restoration responses remain positive and statistically significant across different shoreline elevations and temporal trajectories. This meta-analysis suggests that removing shoreline armoring is an effective technique for restoration projects aimed at improving the health and productivity of coastal ecosystems, and these results may be applicable regionally and globally.