Ecological effects of coastal armoring on sandy beaches

Abstract

Use of coastal armoring is expected to escalate in response to the combination of expanding human populations, beach erosion, and sea level rise along the coasts. To provide a conceptual framework, we developed hypotheses concerning the ecological effects of beach habitat loss associated with coastal armoring. As beaches narrow in response to armoring, dry upper intertidal zones should be lost disproportionately, reducing the habitat types available and the diversity and abundance of macroinvertebrates. Predators, such as shorebirds, could respond to a combination of (i) habitat loss; (ii) decreased accessibility at high tides; and (iii) reduced prey availability on armored beaches. To examine those predictions, zone widths and the distribution and abundance of macroinvertebrates and birds were compared on paired armored and unarmored segments of narrow bluff‐backed beaches in southern California. Our results supported the predictions and revealed some unexpected effects of armoring on birds. Dry upper beach zones were lacking and mid‐beach zones were narrower (>2 times) year‐round on armored segments compared to adjacent unarmored segments. The abundance, biomass and size of upper intertidal macroinvertebrates were also significantly lower on armored segments. Shorebirds, most of which were foraging, responded predictably with significantly lower species richness (two times) and abundance (>3 times) on armored segments. Gulls and other birds (including seabirds), which use beaches primarily for roosting, were also significantly lower in abundance (>4 times and >7 times respectively) on armored segments, an important unexpected result. Given the accelerating pressures on sandy beaches from coastal development, erosion and rising sea levels, our results indicate that further investigation of ecological responses to coastal armoring is needed for the management and conservation of these ecosystems.

Macrofaunal community abundance and diversity and talitrid orientation as potential indicators of ecological long-term effects of a sand-dune recovery intervention

“…2c). The conditions at p1 after the soft-engineering intervention seem to favour in some way the intertidal species, which is an opposite finding with respect to what was observed for the hard-engineering solutions (Bertasi et al, 2007;Dugan et al, 2008;Martin et al, 2005;Sobocinski, 2003). Such differences between the two main beach zones are in agreement with the results of the PCA, indicating that the most influencing environmental variables were those linked to the sediment features that distinguish the intertidal beach zone from the supralittoral one (Table 1).…”

“…Substantial changes to the system ecology were generally observed after these interventions (Brown and McLachlan, 2002;Chapman and Bulleri, 2003;James, 2000;Speybroeck et al, 2006). Frequently, as eroding beaches tend to become narrower, the reduced habitat disposability directly impacts diversity and abundance of biota in the upper intertidal zone, with consequences at all the trophic levels, thus engendering long-term ecological effects on the whole community (Bertasi et al, 2007;Dugan et al, 2008;Martin et al, 2005;Sobocinski, 2003). To monitor the effects of dune-recovery using geotextiles, managers need effective ecological indicators.…”

“…Recent examples of successful application of geotextile tubes come from the coastal zones of USA (Harris and Sample, 2009), Australia (Jackson et al, 2004) and the Republic of Korea (Shin and Oh, 2007), where positive outcomes were obtained in terms of coastal protection. However, very little is known on the effects of dune recovery with geotextiles on biotic communities, if compared to the several studies on the ecological impacts of both beach nourishments (reviewed in Goldberg, 1988;Peterson et al, 2006;Speybroeck et al, 2006) and hard-engineering interventions (Bertasi et al, 2007;Dugan et al, 2008;Martin et al, 2005;Sobocinski, 2003). Negative nourishing effects were observed at the population, community and ecosystem levels on all the biotic components Fanini et al, 2009;Speybroeck et al, 2006).…”

Temporal changes in macrofauna as response indicator to potential human pressures on sandy beaches

“…Fanini et al, 2005;Veloso et al, 2006Veloso et al, , 2008Ugolini et al, 2008) and shoreline modifications such as the construction of seawalls or beach nourishment actions (e.g. Bessa et al, 2013;Dugan and Hubbard, 2006;Fanini et al, 2009). Furthermore, recreational beaches are known to be affected by regular mechanical cleaning (in particular in the supralittoral zone), which is responsible for a considerable reduction of the organic matter available for the fauna on the beach, but also for the disturbance of the sediment, leading to the absence of suitable niches to support these communities, creating a resource-limited environment (McLachlan and Brown, 2006).…”

“…To this regard, over the last years, several studies have been showing the negative effects to macrofaunal communities and/or individual species on beach-aeolian dune environments, when facing particular human disturbances caused by coastal management practices such as beach nourishment projects (e.g. Bessa et al, 2013;Fanini et al, 2009;Jones et al, 2008; and coastal armouring (Dugan and Hubbard, 2006;Dugan et al, 2008;Walker et al, 2008). Still, human recreational activities have been recognised to negatively affect beach fauna due to the intensive use of beaches (Schlacher and Thompson, 2012;Schlacher et al, 2011;Ugolini et al, 2008;Veloso et al, 2008) and to the impact of off-road vehicles (e.g.…”