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Zone II, forests that are ready to be brought into production Zone III, degraded areas that will be closed to allow recovery
Zone IV, areas that will be set-aside for different developments.
The Mangrove Management plans emphasise the need to have close coordination among the various users of the mangrove ecosystem. Although it is now 10 years since the management plans of mainland Tanzania were prepared,
still it is not followed closely and community involvement is minimal Semesi 1998. Collaborative management is being practised in three pilot villages in Tanga: Kipumbwi, Sange and Kisa Ngunyali 1997, and 422 ha of
mangroves have been allocated for trial. The mangrove management project is collaborating with the Tanga Coastal Zone Development Project and local communities. However, the government through its Forest Division
still assumes the overall responsibility. The primary objective of this collaborative management is protection and wise use of mangroves for the benefit of the villagers. The main constraint identified has been limited trained
personnel to carry out the implementation of the management plan and lack of experience of the foresters in involving communities. However, the mangrove management plans of Tanzania have been useful as they are used to
raise awareness on the mangroves. The management plans are now used in the Kenya and Mozambique who are preparing their plans following similar approach.
5.5.9 Condition of the resource good overused depleted degraded pristine
The rate of cutting is high near big population centres and therefore the most degraded mangroves are those close to towns such as that at Mtoni, Kunduchi and Mjimwema in Dar es Salaam, Maruhubi close to Zanzibar town or
those mangroves close to Tanga and Mtwara towns. Some mangroves found in islands in Tanga region such as Ulenge area are also quite degraded because of illegal cutting for export to Kenya and due to easy access by boat.
However some parts of Rufiji and Ruvuma deltas have mangroves that are in very good condition because it is difficult to access them, there is low surrounding population and other alternative sources of firewood and timber
are available to the community. We hardily have pristine mangroves in Tanzania considering the long dependency of coastal communities on the mangrove resources. Many studies Banyikwa and Semesi 1986, Nasser 1994,
Semesi et al 1999, Shunula 1996, etc. show increasing trend in cutting and thus also the degradation of mangroves in Tanzania.
5.5.10 Human impacts
The ecological stability of the mangrove ecosystem is dependent on both upland terrestrial and the coastal estuarine ecosystems with which it is intimately and inseparably linked. Severe erosion, improper agricultural and forestry
practices and pollution from pesticides and herbicides hundreds of kilometres upstream in Catchment areas can all affect mangroves and other elements of the coastal ecosystem. Petroleum prospecting, oil pollution from ships, the
dumping of garbage and sewage as well as various types of industrial chemical pollution in the estuarine environment, boat traffic that increase erosive boat wakes also may have direct negative affects on mangroves.
Selective cutting is the normal practice for subsistence use and this practice usually allows profuse natural regeneration of the mangroves. However, large scale clear felling of mangroves prevent natural regeneration
Germanis 1999, Masawe 1999, Semesi 1987, Semesi et al. 1999 due to alteration of soil and microclimate and few seed bearing trees being left in the plot to act as seed source. In some stands of mangroves such as in Maruhubi and
Chwaka in Zanzibar or Kunduchi and Mtoni in Dar es Salaam, the rate of annual removal of trees from the forest is higher than the mean annual increment and is thus not sustainable. Clearance of mangrove for salt production and
clear cutting for charcoal are the most important in destroying the mangroves of Bagamoyo, Lindi, Zanzibar, Dar es Salaam, Mtwara and Tanga Banyikwa and Semesi 1986, Semesi 1987, 1993, Masawe 1999, von Mitzlaff 1990,
Shunula 1996, Kulindwa et al. 1998, etc.. Intensity of cutting is influenced by the ease of access and closeness to high population density.
Clearing for rice farms takes place in Ruvu and Rufiji delta in Tanzania Semesi 1991, Semesi et. al. 1999, Sørensen 1997. In the Rufiji delta farms cleared from mangroves after approximately the 7th year range from 4
th
to 11
th
year,
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yields fall dramatically and grasses, phragmites and sedges or Derris invade the farms and working the farms becomes a problem. Therefore the farms are usually abandoned after this period. Digging of polychaete worms used as fish bait
in the Sonneratia and Rhizophora zones also result in ecological damage of the mangroves Semesi et al. 1999.
5.5.11 Natural impacts
