Disasters and Ecological Dividends
Changing ecological conditions can themselves provoke emergencies, or aggravate disaster events, by placing concurrent stresses on the environment. Mitigating these stresses and their effects has become an important component in global efforts to ensure environmental security.
This was clearly illustrated in the analysis of the 'Tokage' typhoon (Typhoon no. 23 of 2004) that struck Japan. Deforestation, forest management practices, or agriculture systems can intensify the negative environmental impacts of a storm or typhoon, leading to landslides, flooding, silting and ground/surface water contamination.
While the degree of protection provided by the environment depends on a number of factors, social and natural scientists have been working calculate the "prevention dividends" of protecting the environment. The following examples have been compiled by IUCN:
- A study of the value of conserving upland forests that form the watershed for the Vohitra River in Eastern Madagascar estimated the net present value (NPV)7 of protection benefits at $126,700. This value arises from the reduced costs of flooding and the increased net market value when less paddy is damaged by flooding.
- Sri Lanka's Muthurajawela marsh, a coastal peat bog covering some 3,100 hectares, is an important part of local flood control. The marsh significantly buffers floodwaters from the Dandugam Oya, Kala Oya and Kelani Ganga rivers and discharges them slowly into the sea. The annual value of these services was estimated at more than $5 million, or $1,750 per hectare of wetland area .
- In Malaysia the value of intact mangrove swamps for storm protection and flood control has been estimated at US$ 300,000 per km, which is the cost of replacing them with rock walls.
- The 40,000 hectares of managed mangrove forest in Matang, West Malaysia yield $10 million in timber and charcoal and over $100 million in fish and prawns every year.
- Mangrove forests in southern Thailand provide an estimated $3,679 NPV per ha in coastline protection and stabilization.
- Shoreline stabilisation is also important for inland rivers. In the eastern United Kingdom, the loss of vegetation along riverbanks was estimated at US$ 425 per metre of bank. This is the cost of maintaining artificial bank reinforcement to prevent erosion.
- Mangroves and other wetlands, as well as coral reefs, contribute to coastal protection, as they are able to dissipate wave energy. In recent years, mangrove destruction has resulted in damage to the coastal road going into the Portland Ridge, Jamaica. It has been estimated that the total coastal protection value was around US$3.55 million in NPV or nearly US$400,000 per year (with a ten percent discount rate).
- In Indonesia, the value of coastal protection afforded by intact mangrove forest is estimated at between USD 829/km - USD 1 million/km.
Source: IUCN 2000, "Second IUCN World Conservation Congress", 4-11 October 2000. Report and Background Papers. Gland: World Conservation Union (IUCN)