Case Study

Living Seawalls

Along urbanised coastlines, marine urban infrastructure is increasingly becoming the dominant habitat. Structures such as seawalls, pilings, pontoons and marinas, are built for diverse purposes such as shoreline protection, recreational activities and energy generation. However, these structures destroy natural habitats and can modify the surrounding seafloor, negatively impacting biodiversity and marine ecosystems. Often, these structures remove habitats and natural protective refuges for marine plants and animals, but they also impact the marine ecosystems that humans rely on to provide services such as the maintenance of clean water, carbon sequestration and fisheries production.

As the threat of climate change and global sea-level rise increases, the need to protect coastal populations becomes ever more critical. In most coastal cities, over 50% of the shoreline is made up of seawalls, providing a huge opportunity to increase the ecological value of these flat, artificial structures. Living Seawalls provides an evidence-based solution to achieve this, showing that although marine construction is a large part of the problem, it can also be part of the solution.

Over 20 years of scientific research by the Sydney Institute of Marine Science has gone into developing the Living Seawalls panels, which are an affordable, adaptable and scalable method of ecologically enhancing marine structures. The panels have been designed to mimic the habitat features of natural shoreline ecosystems such as rock pools and crevices. In collaboration with the industrial designers at Reef Design Lab, the panels are first digitally designed, with the size and shape of the design features being informed by measurements taken from natural rocky shorelines. 3D printing technology is used to create reusable moulds of the panel designs. From this mould, concrete panels can be cast and manufactured in large numbers.

Living Seawalls has developed 10 different habitat panel designs, each targeting different features of natural shorelines which benefit diverse groups of marine organisms. Each design also undergoes a series of tests, ensuring they can withstand marine conditions. The panels are designed to fit into scalable mosaics, which can be installed onto new and existing structures, tailored to each site.

The initial Living Seawall panels were used to retrofit existing seawalls in Sydney Harbour. After 1-2 years post-installation, research has shown that these Living Seawalls support at least 36% more species than unmodified seawalls with many years of marine growth, with as many as 115 species of invertebrates and seaweeds living and growing on the panels. This is similar to what can be found on nearby natural rocky reefs, which are hotspots of biodiversity. In addition, fish like to shelter in the habitat provided and benefit from the food sources found on the panels. By two years post-installation, a greater number of fish was recorded in and around the Living Seawalls panels than on unmodified, flat seawalls. The Living Seawalls panels have been engineered to last at least 20 years, and it is likely that as time elapses, Living Seawalls will serve as a home to, and attract, even more species.

At the Rushcutters Bay Living Seawall in Sydney Harbour, the panels have attracted and bolstered the numbers of oysters and mussels, enhancing particle removal from the water and leading to improved water quality. In turn, this improves recreational activities including swimming, fishing and water sports in and around urban oceans.

Over 2,500 Living Seawalls panels have been installed around the world and these have been an important educational tool in highlighting the threats posed to marine biodiversity due to coastal development, and the potential to revive degraded marine ecosystems using innovative technologies. Programmes have been run for primary-, secondary- and tertiary-level students, and involve hands-on activities to engage students with the ecological aims of the initiative, learning about marine habitat loss and how green-engineering solutions can revive marine communities.

As the need to adapt to the threat of climate change in coastal areas increases, Living Seawalls bolsters the resilience provided by the seawalls and enables coastal defences to protect communities from rising sea levels, whilst also enhancing the ecological value of the marine structures. The initiative highlights how artificial marine infrastructure can be adapted to enhance its resilience and deliver important social and environmental outcomes.

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