A sea wall is the obvious answer to a rising ocean — solid, visible, reassuring. It is also expensive to build and expensive to maintain.
Natural defences work differently. Mangroves and healthy reefs absorb wave energy, trap sediment and, unlike concrete, can grow with the sea rather than against it.
The trade-offs are real. Living barriers need space, time and protection from the very development they are meant to shield.
The likeliest future, planners say, is a blend: hard structures where they must stand, and restored coastlines wherever nature can do part of the work.
