Ecological Consequences of Shoreline Hardening: A Meta-Analysis

Abstract

Protecting coastal communities has become increasingly important as their populations grow, resulting in increased demand for engineered shore protection and hardening of over 50% of many urban shorelines. Shoreline hardening is recognized to reduce ecosystem services that coastal populations rely on, but the amount of hardened coastline continues to grow in many ecologically important coastal regions. Therefore, to inform future management decisions, we conducted a meta-analysis of studies comparing the ecosystem services of biodiversity (richness or diversity) and habitat provisioning (organism abundance) along shorelines with versus without engineered-shore structures. Seawalls supported 23% lower biodiversity and 45% fewer organisms than natural shorelines. In contrast, biodiversity and abundance supported by riprap or breakwater shorelines were not different from natural shorelines; however, effect sizes were highly heterogeneous across organism groups and studies. As coastal development increases, the type and location of shoreline hardening could greatly affect the habitat value and functioning of nearshore ecosystems.

Eco‐engineering urban infrastructure for marine and coastal biodiversity: Which interventions have the greatest ecological benefit?

“…Urban infrastructure impacts on natural ecosystems in a variety of ways, including habitat loss and fragmentation, as well as modification of ecological connectivity, ecosystem functioning and services, and the physico‐chemical environment (Bishop et al., ; Fischer & Lindenmayer, ; LaPoint, Balkenhol, Hale, Sadler, & Ree, ; McKinney, ). The net effect is urbanised ecosystems that are fundamentally different in structure and function to the natural habitat which they displace (Airoldi, Turon, Perkol‐Finkel, & Rius, ; Gittman, Scyphers, Smith, Neylan, & Grabowski, ; Heery et al., ). In some instances the need for urban infrastructure may be circumvented by adding or restoring natural habitats that enhance biodiversity and provide essential functions (Dethier, Toft, & Shipman, ; Sutton‐Grier, Wowk, & Bamford, ).…”

Investing in Natural and Nature-Based Infrastructure: Building Better Along Our Coasts

“…For instance, NNBI approaches often do not conform to current permit and zoning regulations. USACE permitting of bulkheads and living shorelines is just one example of where U.S. federal and state regulations have historically inhibited and even discouraged the use of NNBI in preference of traditional built infrastructure, despite the clear socio-ecological benefits of NNBI [9,14,20]. However, USACE has made progress towards addressing this challenge: in March 2017, it implemented Nationwide Permit 54 for living shorelines [52], which will hopefully facilitate the implementation of NNBI shoreline projects.…”

“…Dams, levees, canals, and bridges constructed in and across U.S. rivers and waterways have created drinking water reservoirs, reduced flood risk for people and property, generated hydroelectric power, expanded transportation options, improved navigation, and helped grow the U.S. economy, but not without significant socio-ecological consequences [3,4]. In some cases, built infrastructure (e.g., dams, undersized culverts, seawalls, and water-diverting levees and canals) has resulted in significant declines in the abundance of aquatic organisms (e.g., economically valuable anadromous fish species) and the diversity of key habitats, such as the Florida Everglades [4][5][6][7][8][9]. Further, this infrastructure has resulted in flood-related human fatalities and property damage when it has failed [10,11].…”

Florida’s Oceans and Marine Habitats in a Changing Climate

“…Without wetland buffers, pulsed nutrients and sediment loads to coastal water bodies are likely to increase. Loss of wetlands also and eliminate an important larval to juvenile fish and shellfish habitat, further reducing fisheries production potential in these coastal ecosystems (Gittman et al 2016).…”