Mangrove Restoration - Costs and Benefits of Successful Ecological Restoration
The costs to successfully restore both the vegetative cover and ecological functions of a mangrove forest have been reported to range from USD$225/ha to USD$216,000/ha. Unpublished data would indicate that the even higher costs, as much as USD$500,000/ha, has been spent on individual projects. These are obviously cost prohibitive amounts for most countries seeking to restore damaged mangroves. I divide the types of mangrove restoration projects into three categories: (1) planting alone, (2) hydrologic restoration, with and without planting, and (3) excavation or fill, with and without planting. The first type, planting only, although inexpensive (e.g.: USD$100-200/ha) usually does not succeed due to a failure to appreciate the physiological tolerances of mangroves to tidal inundation. Even if it works, the result is often replacement of one productive marine habitat, like seagrass meadows with mangroves, a questionable trade-off. The second type, hydrologic restoration, can be done for similar costs, and with proper planning has a high success rate. Successful restoration of abandoned shrimp aquaculture ponds is an example of this method. Planting should only be done if natural recolonization fails, and can double the cost of a project. Scientific data indicates that using this method, ecological functions are quickly restored, with fish populations typically reaching reference site diversity and densities within 5 years. The third type, excavation and fill, is the most expensive due to the high costs of large scale earthmoving. It is only a viable option in more developed countries, and may not be a cost-effective means of restoration except under limited circumstances.