Mangroves: sustainable management in Bangladesh

Bangladesh faces two mangrove management challenges: the first is the management of the resources of the Sundarbans natural mangrove areas on a sustainable basis, while protecting the high levels of biodiversity. The second challenge is to manage the planted mangroves of the Bangladeshi shoreline under competing, and sometimes conflicting, management objectives and expectations. Management of the Sundarbans has been based on selective felling, with felling cycles and minimal DBHs adjusted for each of the main commercial species. The allowable annual cut is determined by ongoing forest inventories to ensure harvesting is equal or lower than the growth and reproduction rate. However, despite the adoption of sustainable yield, some degradation of the mangroves is occurring, the primary causes being human interference (e.g. illegal harvesting and pollution) and changed hydroedaphic conditions (e.g. erosion and accretion, and increased soil salinity due to water abstraction). The protection from cyclone damage afforded by the Sundarbans mangrove forests, led the Forestry Department in 1966 to commence a programme of planting mangroves outside the protective coastal embankments in order to provide greater protection for the other coastal areas. Harvestable size is reached in 15–25 years, but prior to harvest, a new crop must be established, so that coastal lands are not unvegetated and liable to erosion. The mangrove greenbelt has brought many obvious benefits, but despite these benefits, there are problems which are not silvicultural, but result from population pressure; illicit felling of trees and unlawful grazing of coastal lands, threaten the mangroves and the encroachment in some areas by shrimp farms comprises a major concern. The protective benefits from the sustainable management of natural and planted mangroves in Bangladesh are beyond dispute – the minimal damage suffered by the coastal areas from the Indian Ocean tsunami on 26 Dec 2004 can be ascribed simply to the good condition of the natural and planted mangrove greenbelt of that country. When viewed together with the benefits that mangrove habitats bring to biodiversity conservation, it would seem to be obvious that mangrove greenbelts should be actively promoted. What has been shown in Bangladesh is that the silvicultural expertise needed has been developed.