Marine urbanisation in Singapore and potential mitigation strategies

Globally, habitat loss associated with land reclamation, coastal defences, and shoreline development is becoming increasingly prevalent. Over the last 200 years Singapore has reclaimed 169 km2 of land, and provides... [ view full abstract ]

Globally, habitat loss associated with land reclamation, coastal defences, and shoreline development is becoming increasingly prevalent. Over the last 200 years Singapore has reclaimed 169 km² of land, and provides a striking example of large-scale and intense urbanisation. The majority of Singapore's mangrove forests, coral reefs, rocky shores and sand/mudflats disappeared between the 1920s and 2000s. Only 17% of its coastline is natural, with the remainder dominated by seawalls. When comparing the species assemblages on seawalls with their natural analogs: rocky shores, we found that, as in temperate regions, seawalls in Singapore host lower diversity but share a substantial number of species with rocky shores. Stable isotope analyses showed that turf algae was the largest contributor to the diets of intertidal herbivores, but was present in significantly lower abundances on seawalls. These results are not unexpected, as seawalls are generally designed with civil engineering goals and do not function as surrogates for natural habitats. In Singapore, they are made of materials chosen for strength, not for their ability to attract wildlife. They are structurally “simple” compared to rocky shores, and experience very high temperatures. Given the prevalence of artificial coastal defences in Singapore, ‘hard’ engineering mitigation options such as retrofitting topographically complex “tiles” made of materials that encourage colonisation and offer thermal refuges provide the most practical approach to enhancing seawall biodiversity. Here, I will present what we have learnt from our ecological engineering experiences in Singapore and discuss how our findings provide important practical insights for successful seawall reconciliation.