The mangrove ecosystem is one of the important coastal wetlands that appears to be both important sink of global carbon and exporters of nutrients that help sustain the productivity of estuarine and other coastal ecosystems. Mangroves are open ecosystems that straddle the land and the sea, from freshwater to seawater, often with distinct zones of plant and animal species. They are closely linked with the adjacent landward catchment and the seaward marine system. Mangroves and other coastal wetlands are highly complex and productive ecosystems and support important coastal and nearshore fisheries. Despite these unique physical, biological and economical functions, mangroves and other coastal wetlands are being destroyed, degraded and destroyed globally on a large scale through over-exploitation of their potentially renewable products and through conversion to rice farms, shrimp-farms and salt evaporation ponds with little regard for the consequences. This study was concerned with the effects of rice cultivation in the mangrove forests of the Rufiji delta (06°55'S; 39°38'E), Tanzania. Aerial photographs from a particular mangrove forest area were obtained in the following sequence: 1965, in which the forest was relatively undisturbed; 1977, in which the forest was moderately disturbed and 1988, in which the forest was most disturbed for rice cultivation. Rice farms were visited in the Rufiji delta in September 1999, and rice farmers from different areas and age groups interviewed about the functioning of their rice fields in order to obtain socio-economic data. Updated land-use maps could be constructed on the basis of field observation. The results from land use maps resumed in the illustration of an interpretation key that provides an effective tool for future management of the Rufiji delta mangrove forest resource. Comparison of the three land-use maps showed that mangrove forest had been reclaimed for rice cultivation. The Mangrove Management Plan of mainland Tanzania suggests immediate intervention and planning in the western part of the Rufiji delta, where rice growing communities, in their practice of shifting cultivation, clear new mangrove areas every year. However, this expansion of rice farms does not collaborate with this conservation account. Other factors that have been reported to have negative effects on the mangrove forests in this area are also mentioned. |
