Effects of Local Shoreline and Subestuary Watershed Condition on Waterbird Community Integrity: Influences of Geospatial Scale and Season in the Chesapeake Bay

Abstract

In many coastal regions throughout the world, there is increasing pressure to harden shorelines to protect human infrastructures against sea level rise, storm surge, and erosion. This study examines waterbird community integrity in relation to shoreline hardening and land use characteristics at three geospatial scales: (1) the shoreline scale characterized by seven shoreline types: bulkhead, riprap, developed, natural marsh, Phragmites-dominated marsh, sandy beach, and forest; (2) the local subestuary landscape scale including land up to 500 m inland of the shoreline; and (3) the watershed scale >500 m from the shoreline. From 2010 to 2014, we conducted waterbird surveys along the shoreline and open water within 21 subestuaries throughout the Chesapeake Bay during two seasons to encompass post-breeding shorebirds and colonial waterbirds in late summer and migrating and wintering waterfowl in late fall. We employed an Index of Waterbird Community Integrity (IWCI) derived from mean abundance of individual waterbird species and scores of six key species attributes describing each species' sensitivity to human disturbance, and then used this index to characterize communities in each subestuary and season. IWCI scores ranged from 14.3 to 19.7. Multivariate regression model selection showed that the local shoreline scale had the strongest influence on IWCI scores. At this scale, percent coverage of bulkhead and Phragmites along shorelines were the strongest predictors of IWCI, both with negative relationships. Recursive partitioning revealed that when subestuary shoreline coverage exceeded thresholds of approximately 5% Phragmites or 8% bulkhead, IWCI scores decreased. Our results indicate that development at the shoreline scale has an important effect on waterbird community integrity, and that shoreline hardening and invasive Phragmites each have a negative effect on waterbirds using subestuarine systems.

Impacts of Coastal Land Use and Shoreline Armoring on Estuarine Ecosystems: an Introduction to a Special Issue

“…In addition, Phragmites has invaded natural wetlands along the US east coast (Chambers et al 1999) and in the continental US (Kulmatiski et al 2010;Larson et al 2011;Bourgeau-Chavez et al 2013). Invasion by Phragmites can negatively impact wetland structure and function by altering dynamics in fish (Jones et al 2014; Jones and Able 2015) and bird (Prosser et al 2017, this issue) communities. However, the consequences of invasion may not all be negative because Phragmites patches are not biological deserts, especially for animals (Kiviat 2013;Dibble and Meyerson 2014).…”

Human Influence at the Coast: Upland and Shoreline Stressors Affect Coastal Macrofauna and Are Mediated by Salinity

“…can add sediments, nutrients, pesticides, and contaminants to water (Jordan et al 1997;Paul and Meyer 2001;Gregg et al 2015). This can negatively impact benthic invertebrates (Hale et al 2004;King et al 2005), fish (Sanger et al 2004), and waterbird communities (DeLuca et al 2008;Prosser et al 2017). Pollutants can reduce abundance, diversity, and trophic complexity of benthic species in favor of small, short-lived, opportunistic species, such as deposit-feeding polychaetes (Pearson and Rosenberg 1978;Warwick and Clarke 1993;Inglis and Kross 2000).…”

A New Food System for the Chesapeake Bay Region and a Changing Climate

“…About 63 different species of water birds require those transitions for feeding, mating and nesting along the shores of the Bay’s tributaries. As little as 5% shoreline hardening significantly reduces water bird habitat and counts (Prosser et al 2017 ). As of 2016, 18% of the shoreline of the Bay and its major tributaries had been hardened, substantially reducing habitat (Mitchell 2016 ).…”