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 eco-engineering 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.
Highlights
Coastlines worldwide are becoming increasingly vulnerable to flooding, erosion and degradation due to rising sea level, stormier seas and increased coastal urbanisation (McGranahan et al 2007; Halpern et al 2008; Tessler et al 2015)
The human population within 100 km of the coastline is disproportionally higher compared to inland areas (Small and Nicholls 2003; McGranahan et al 2007), with much of this population concentrated in densely packed urban areas (Firth et al 2016a; Todd et al 2019)
There is impetus among stakeholders to work with natural processes where possible to preserve biodiversity and maintain valuable ecosystem services (Evans et al 2017)
Summary
Coastlines worldwide are becoming increasingly vulnerable to flooding, erosion and degradation due to rising sea level, stormier seas and increased coastal urbanisation (McGranahan et al 2007; Halpern et al 2008; Tessler et al 2015). Where and when human intervention is needed for reasons of public safety, infrastructure protection or energy development, the use of “soft” engineering approaches should be prioritised if possible (Dafforn et al 2015a; Morris et al 2018a) These interventions typically involve working with nature, such as the modification or removal of artificial structures to allow the sea to re-inundate previously reclaimed land (commonly called “managed realignment”; French 2006; Masselink et al 2017; MayerPinto et al 2017), or using vegetation, sand-fills and sand nourishment as coastal protection (Stive et al 2013; Hanley et al 2014; Morris et al 2018a). Various types of structures are considered in turn, with guidance given on appropriate eco-engineering interventions (Supplementary Information Tables 1–4), and generic and contextual considerations on application of eco-engineering designs are discussed
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