The overall aim of this proposal is to enhance native biodiversity on coastal defences in Singapore using ecological engineering principles. The combination of coastal urban development and climate change associated threats has resulted in a rapid and worldwide increase in the construction of hard defences, such as seawalls. These are generally designed with civil engineering goals and do not function as surrogates for the natural habitats they replace. Therefore ecosystems services and resilience are lost. The ‘grand challenge’ of how to enable seawalls to support an abundant and diverse array of species will be addressed through a unique synthesis of ecology, materials science, microbiology, and fluid mechanics.

By the next decade, approximately three quarters of the world’s population will reside in ‘coastal zones’. Coastal land is in high demand and development and land reclamation is occurring at huge scales. In addition, the risks of sea level rise and more intense storms, putatively caused by climate change, have resulted in an urgent need for shoreline protection. As a result, man-made coastal defences are quickly, and on a global scale, becoming the primary means of mitigating such risks.

Seawalls differ from natural shores in fundamental ways. They are usually very steep, increasing the effects wave impact and compressing the intertidal zone, such that species which are naturally spaced far apart become superimposed. Seawalls lack microhabitats (e.g. pits, rock-pools, overhangs and crevices) and structural complexity as well as frequently being made from materials that may not be well-suited for colonisation and/or exhibit thermal properties that result in high temperatures during emersion.

Despite these adverse consequences, only recently have researchers examined the ecological impacts of seawalls and/or suggested ways to boost biodiversity. Realising that these structures are permanent, there is now greater interest in maximising their ecological value. Designing urban infrastructure in a manner congruent with ecological principles is known as ecological engineering. This concept is the core of our proposal.

Singapore is the quintessential land-scarce island city state. In the last 200 years, 169 km² of land has been reclaimed from the sea (figure on the side). Only 17.1% of its coastline is natural, while most (63.3%) is seawall (Lai et al., 2015, figure on the side). This makes it an ideal location for the development of strategies and techniques that enhance native biodiversity on hard coastal defences.