Page 53 - Envision 17

Policy
Nature- Enhanced Coastal Defence
Coastal urbanisation has led to a proliferation of seawalls that enclose reclaimed land and prevent coastal
erosion. Biodiversity of the intertidal and shallow seas is reduced as these zones
get eliminated. Increasing the height of seawalls is a common response to sea-
level rise. Faced with this new long-term situation, consideration should be given to incorporating nature with coastal defence. This will improve the benefits of ecosystem services that coastal and marine biodiversity offer. It is a response that aligns with sustainable development.
L.M. Chou
National University of Singapore
Defending the coastline against strong waves that cause erosion has conventionally been accomplished
by constructing a solid wall or revetment. These hard structures commonly obliterate the intertidal zone as they provide an abrupt separation of the land that they retain and the sea on the other side. At the same time, breakwaters can be installed further offshore or extended seaward from land to reduce the full energy of waves breaking on shore. In nature, such protective functions are provided by coastal and marine habitats such as coral reef, seagrass and mangrove. This service is provided free of charge. A simple valuation of such a service is how much it would cost to construct a revetment, a necessary action if degraded habitats can no longer provide it. What is not factored in the valuation are all the other important services such as carbon sequestration, food production and nursery function that the habitats provide perpetually when adequately managed. These amount to many times more than what the revetment costs.
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