The Early Shorebird Will Catch Fewer Invertebrates on Trampled Sandy Beaches

Abstract

Many species of birds breeding on ocean beaches and in coastal dunes are of global conservation concern. Most of these species rely on invertebrates (e.g. insects, small crustaceans) as an irreplaceable food source, foraging primarily around the strandline on the upper beach near the dunes. Sandy beaches are also prime sites for human recreation, which impacts these food resources via negative trampling effects. We quantified acute trampling impacts on assemblages of upper shore invertebrates in a controlled experiment over a range of foot traffic intensities (up to 56 steps per square metre) on a temperate beach in Victoria, Australia. Trampling significantly altered assemblage structure (species composition and density) and was correlated with significant declines in invertebrate abundance and species richness. Trampling effects were strongest for rare species. In heavily trafficked plots the abundance of sand hoppers (Amphipoda), a principal prey item of threatened Hooded Plovers breeding on this beach, was halved. In contrast to the consistently strong effects of trampling, natural habitat attributes (e.g. sediment grain size, compactness) were much less influential predictors. If acute suppression of invertebrates caused by trampling, as demonstrated here, is more widespread on beaches it may constitute a significant threat to endangered vertebrates reliant on these invertebrates. This calls for a re-thinking of conservation actions by considering active management of food resources, possibly through enhancement of wrack or direct augmentation of prey items to breeding territories.

Managing birds of conservation concern on sandy shores: How much room for future conservation actions is there?

“…For species with more specific habitat requirements (especially during nesting), management of human disturbance is much more important (Schlacher, Weston, Lynn, & Connolly, ; Weston et al, ). Indeed, human recreational use can significantly degrade habitat quality (Maslo, Leu, et al, ; Schlacher et al, ), even for more tolerant species, and negatively impact reproductive output (Schlacher, Carracher, et al, ). Therefore, extending human disturbance protections will also likely confer a significant conservation benefit by improving nest success and chick survival when birds breed in protected areas, ultimately increasing population growth (Cohen et al, ; McGowan et al, ).…”

“…), which are prevented by beach‐raking and trampling by vehicles and pedestrians (Kelly, ; Priskin, ; Šilc, Caković, Küzmič, & Stešević, ). Such activities also reduce the abundance of prey resources (Schlacher et al, ; Schlacher, Carracher, et al, ). Removing these stressors may reestablish these coastal processes, thereby increasing habitat quality.…”

“…Our models predict extensive potential nesting areas for habitat requirements (especially during nesting), management of human disturbance is much more important (Schlacher, Weston, Lynn, & Connolly, 2013;Weston et al, 2014). Indeed, human recreational use can significantly degrade habitat quality (Maslo, Leu, et al, 2016;Schlacher et al, 2015), even for more tolerant species, and negatively impact reproductive output (Schlacher, Carracher, et al, 2016). Therefore, extending human disturbance protections will also likely confer a significant conservation benefit by F I G U R E 7 Example map of changes to the location and extent of habitat suitable for nesting by American oystercatchers (colored areas) on Island Beach State Park, New Jersey, USA (a) without human disturbance protections, (b) under the current levels of protection, and (c) under a scenario in which all potential habitat is protected from human disturbance.…”

“…At a minimum, they identify locations that are not likely to change in suitability once protected from human disturbance (Figure 8 (Kelly, 2016;Priskin, 2003;Šilc, Caković, Küzmič, & Stešević, 2017). Such activities also reduce the abundance of prey resources Schlacher, Carracher, et al, 2016). Removing these stressors may reestablish these coastal processes, thereby increasing habitat quality.…”

Tourism impacts on benthic communities of sandy beaches

“…Recreational activities are increasingly observed on sandy beaches, boosting the tourism industry around the world, and urban infra‐structure is essential to attract tourists (Rolfe & Gregg, ). As a consequence of urban occupation, several human activities such as dune vegetation suppression, coastal armoring, beach cleaning and grooming, vehicle traffic and trampling now affect macrofauna communities worldwide (Schlacher et al., ). To distinguish the effects of trampling from generalized and broader urbanization impacts is challenging and most studies deal with the difficult to detect isolated mechanisms responsible for community structure changes in urban beaches.…”