Design catalogue for eco-engineering of coastal artificial structures: a multifunctional approach for stakeholders and end-users

Abstract

Coastal urbanisation, energy extraction, food production, shipping and transportation have led to the global proliferation of artificial structures within the coastal and marine environments (sensu "ocean sprawl"), with subsequent loss of natural habitats and biodiversity. To mitigate and compensate impacts of ocean sprawl, the practice of ecoengineering of artificial structures has been developed over the past decade. Eco-engineering aims to create sustainable ecosystems that integrate human society with the natural environment for the benefit of both. The science of eco-engineering has grown markedly, yet synthesis of research into a user-friendly and practitioner-focused format is lacking. Feedback from stakeholders has repeatedly stated that a "photo user guide" or "manual" covering the range of eco-engineering options available for artificial structures would be beneficial. However, a detailed and structured "user guide" for eco-engineering in coastal and marine environments is not yet possible; therefore we present an accessible review and catalogue of trialled eco-engineering options and a summary of guidance for a range of different structures tailored for stakeholders and end-users as the first step towards a structured manual. This work can thus serve as a potential template for future eco-engineering guides. Here we provide suggestions for potential eco-engineering designs to enhance biodiversity and ecosystem functioning and services of coastal artificial structures with the following structures covered: (1) rock revetment, breakwaters and groynes composed of armour stones or concrete units; (2) vertical and sloping seawalls; (3) over-water structures (i.e., piers) and associated support structures; and (4) tidal river walls.

A global analysis of complexity–biodiversity relationships on marine artificial structures

“…Our results support previous suggestions that the addition of complexity to the homogenous, flat surfaces of coastal defence structures has the potential to improve ecological outcomes (O'Shaughnessy et al, 2020). As compared to the natural habitats they replace, topographically simple artificial structures commonly support reduced native biodiversity (Airoldi et al, 2015).…”

“…There has been increasing interest in how complexity might be incorporated into the design of marine urban structures so as to enhance their ecological value (O'Shaughnessy et al, 2020). The addition of complexity to topographically homogenous marine urban structures has been proposed as a mechanism by which the overall richness and abundances of key functional groups might be enhanced (Strain, Olabarria, et al, 2018).…”

Greening of grey infrastructure should not be used as a Trojan horse to facilitate coastal development

“…In an effort to promote more sustainable marine built environments, IGGI is being used to improve multifunctionality; in particular the ecological value of hard infrastructure. The field has flourished recently (Strain et al., 2018), with many successful examples emerging (see O'Shaughnessy et al, 2020 for review). It remains a comparatively young science, however, and has not been subject to the long‐term experimentation, implementation and critical evaluation that are necessary before being considered a mainstream solution.…”

“…The emerging field of IGGI in the marine environment is producing numerous examples of multifunctional structures yielding multiple biodiversity benefits. This has been achieved through myriad techniques, including manipulating building materials composition, building in topographic complexity and transplanting organisms directly onto substrata (see O'Shaughnessy et al, 2020 for review). To date, much of this has been done by the research community on experimental scales and has typically been applied retrospectively to existing artificial structures.…”

Rocky shores as tractable test systems for experimental ecology

“…Worldwide experimental trials have tested the efficacy of different types of crevices (Coombes et al ., 2015), complexity of tiles (Loke et al ., 2014, 2015), boulder size and mix in gabions (Firth et al ., 2014) and retro-fitted artificial rockpools (Browne & Chapman, 2014; Evans et al ., 2016). Guidelines on practice are emerging (Morris et al ., 2019; O'Shaughnessy et al ., 2020) and this approach is now entering the planning (Evans et al ., 2016; Evans et al ., 2019) and engineering mainstream (Burcharth et al ., 2007). Additionally along the way some interesting insights have emerged on rock pool ecology (Firth et al ., 2013), topographic complexity and diversity (Loke et al ., 2016; Loke & Todd, 2016), mobile predators using the intertidal zone (Morris et al ., 2017), connectivity of matter and propagules (Bishop et al ., 2017; Heery et al ., 2017) plus difficult-to-study boulder shores (Chapman, 2017).…”