Arguments for protection: disaster mitigation
Preventing flood damage
One of the most significant social and economic benefits provided by wetlands is flood mitigation and control.
Upstream wetlands can store water from heavy rainfalls, thereby preventing possible flooding downstream. Downstream wetlands can additionally slow floodwaters and provide space for water overflowing from rivers, thereby reducing a flood’s destructiveness.
The economic value of this is huge. For example, the flood attenuation function of two reserves in Sri Lanka’s Muthurajawela Marsh – located near the country’s most densely populated and economically important urban area – is worth an estimated US$5 million each year.
Despite this, wetlands are often seen as having little or no value. They are routinely drained and converted to agriculture or for human habitation – which has reduced their capacity to protect against flooding. And perversely, the subsequent construction of levees and dams on rivers to control floods has often had the reverse effect.
Clearly, it is much more cost-effective to simply protect wetlands in the first place.
Preventing coastal damageMangroves, coral reefs, sand dunes, and other coastal habitats provide significant protection against damage from hurricanes, cyclones, storm surges, and tsunamis. Mangrove forests, for example, can absorb 70-90% of the energy of wind-generated waves, while the protective function of coral reefs is estimated to be worth US$9 billion per year globally.
When these habitats are cleared or destroyed, ocean water can penetrate much further inland, endangering people, homes, farmland, and livelihoods.
The 2004 Indian Ocean tsunami provides a good illustration of this. Coastal communities in South and Southeast Asia that had maintained healthy coastal habitats suffered much less from the tsunami than those with damaged coral reefs and cleared mangroves and coastal vegetation.
With an estimated 60% of the world’s population living within 60 km of a coast, the protection provided by natural coastal habitats clearly makes them worth saving.