Design Options, Implementation Issues and Evaluating Success of Ecologically Engineered Shorelines

Abstract

Human population growth and accelerating coastal development have been the drivers for unprecedented construction of artificial structures along shorelines globally. Construction has been recently amplified by societal responses to reduce flood and erosion risks from rising sea levels and more extreme storms resulting from climate change. Such structures, leading to highly modified shorelines, deliver societal benefits, but they also create significant socioeconomic and environmental challenges. The planning, design and deployment of these coastal structures should aim to provide multiple goals through the application of ecoengineering to shoreline development. Such developments should be designed and built with the overarching objective of reducing negative impacts on nature, using hard, soft and hybrid ecological engineering approaches. The design of ecologically sensitive shorelines should be context-dependent and combine engineering, environmental and socioeconomic considerations. The costs and benefits of ecoengineered shoreline design options should be considered across all three of these disciplinary domains when setting objectives, informing plans for their subsequent maintenance and management and ultimately monitoring and evaluating their success. To date, successful ecoengineered shoreline projects have engaged with multiple stakeholders (e.g. architects, engineers, ecologists, coastal/port managers and the general public) during their conception and construction, but few have evaluated engineering, ecological and socioeconomic outcomes in a comprehensive manner. Increasing global awareness of climate change impacts (increased frequency or magnitude of extreme weather events and sea level rise), coupled with future predictions for coastal development (due to population growth leading to urban development and renewal, land reclamation and establishment of renewable energy infrastructure in the sea) will increase the demand for adaptive techniques to protect coastlines. In this review, we present an overview of current ecoengineered shoreline design options, the drivers and constraints that influence implementation and factors to consider when evaluating the success of such ecologically engineered shorelines.

Little evidence that lowering the pH of concrete supports greater biodiversity on tropical and temperate seawalls

“…In response to these threats, ecological engineering -the integration between engineering princip les and maximised ecological value -has been increasingly adopted in the marine environment (Chapman et al 2018, Strain et al 2018. The aim is to alleviate the negative impacts associated with artificial structures and to increase their ecological functioning (Morris et al 2019). In particular, 'hard' engineering, the physical modification of existing sea walls or use of habitat enhancement units (Chapman & Underwood 2011), has been experimented with in several countries, both temperate and tropical (Dafforn et al 2015, Firth et al 2016b, Loke et al 2019c).…”

Towards an urban marine ecology: characterizing the drivers, patterns and processes of marine ecosystems in coastal cities

“…It is presently unclear whether urban marine ecosystems meet all criteria of 'novel ecosystems' (Morse et al 2014), but their trajectory is undeniably shaped by the way in which coastal cities develop and modify the marine environment (Dafforn et al 2015). Given the potential of marine assemblages to provide ecosystem services to urban populations, as well as recent success in the realm of eco-shoreline design (Toft et al 2013, Morris et al 2019, it may be more helpful to consider urban marine ecosystems and their future trajectory within the framework of 'designed ecosystems' (Higgs 2017) or 'reconciliation ecology' (Rosenzweig 2003a). While both of these frameworks arose with the realization that some systems have been so severely altered and/or degraded it is practically impossible to apply conventional restoration practices (or expect the system to shift back towards a 'historic' or 'pre-disturbed' state), conceptually they are fundamentally different in their intent, starting point and developmental trajectory (Hunter andGibbs 2007, Higgs 2017).…”

“…Given that more human-made shorelines are expected to be built in the foreseeable future, it is critical to find ways to increase their ecological and social value while maintaining their engineering function (Borsje et al 2011, Loke et al 2019a). The ecological engineering of human-made shoreline structures is a new but dynamic field, and there is often a tradeoff between taking time to understand these habitats as a system, and the urgency or desire to implement practical solutions (Morris et al 2019). Knowledge of urban shoreline ecosystems and of strategies that effectively enhance ecosystem functioning and services should improve over time, as ecological enhancement and blue/green infrastructure projects become more common and are applied in a broader variety of urban marine environments (Pontee et al 2016).…”

Developing a nature-based coastal defence strategy for Australia

“…These strong knowledge alliances among different disciplines, research institutes, government and industry are supported by an organisational platform (Dutch network of coastal science) that coordinate yearly conferences to facilitate collaboration (Borsje et al 2017). Interdisciplinary teams are essential to the evaluation of nature-based coastal defence (Morris et al 2019b). This is not only from the ecological and engineering perspectives of understanding how to design nature-based solutions but also from economic and socio-political perspectives to understand their costeffectiveness compared to traditional structures, social acceptance and regulation.…”

“…Further, these solutions need to be industry accredited (i.e., by Engineers Australia) with guidelines made available to coastal managers and contractors to inform on-ground implementation. Key questions to be answered in guidelines are listed in Table 1 (for further discussion see also, Bouma et al 2014;Mitchell and Bilkovic 2019;Morris et al 2019b). These guidelines need to be accompanied by state policy that can be acted on by coastal managers.…”