Shoreline armoring removal: assessment of restoration effectiveness in the Salish Sea

Shoreline armoring removal is becoming a common restoration technique in the nearshore of the Salish Sea, yet we lack a comprehensive understanding of the ecological benefits obtained, and how such an understanding could be used to inform management recommendations and educate diverse audiences. To address this knowledge gap, we studied effects of shoreline armor removal at 10 sites, expanding the spatial framework of what was previously known by collaborating across academic (University of Washington), agency (Washington Department of Fish and Wildlife), and citizen science groups. Each site had three beach types of: (1) restored beaches with armoring removed 1-11 years ago, with a mean of four years, (2) armored beaches altered by bulkheads or riprap, and (3) un-armored reference beaches with more natural conditions. We sampled eight metrics of physical and biological conditions, focusing on supratidal and upper intertidal elevations most affected by armoring and targeted by restoration actions: beach wrack, wrack invertebrates, sediments, terrestrial insects, riparian vegetation and logs, beach profiles, forage fish habitat, and stable isotopes of beach-hopper amphipods to reveal ratios of marine and terrestrial food sources. These metrics spanned the functions of beach stability, ecological diversity, and food web support for juvenile salmon and birds. Results indicated that some beach metrics restore quickly, such as wrack accumulation, while others take longer, such as log accumulation. Sediment sizes at restored beaches approximated those of reference beaches, and were appropriate for forage fish spawning. In general, terrestrial-associated metrics were greater at reference beaches, although there was evidence that insect diversity and logs with plant growth increased when beaches were restored greater than four years. This implies that restored beach functions increase through time, providing improved support for forage fish, salmon, and birds