2.1. STATUS OF FOREST RESOURCES
2.2. UTILIZATION OF TREES
2.3. MAJOR THREATS
Tanzania contains about 33.5 million hectares of forests and woodlands representing about 40 percent of the total land area (MNRT, 1998). These forest ecosystems are categorized as forests (3.4 percent), mangroves (0.3 percent) and woodlands (96.3 percent). About 37.3 percent of the forest has been gazetted as forest reserves, 5.96 percent are forests and woodlands in national parks and 56.74 percent being non reserved forest land. A modest area of 80 000 hectares of the gazetted area owned by the government is under plantation forestry and about 1.6 million hectares are under water catchment management.
In Tanzania, wood based energy consumption is estimated to account for more than 92 percent of the total energy consumption per capital and estimated at about 1 m3 per year[1] (FBD, 1992; MNRT, 1998). Further, its contribution to the Gross Domestic Product (GDP) is in the range of 2-3 percent and about 10 percent of the country’s registered exports. Although, forest land covers an extensive area (40 percent), its recorded contribution to the national economy is modest due to inefficient short comings in record keeping and environmental accounting.
2.2.1. Timber
2.2.2. Building poles and fuelwood
2.2.3. Non-wood forest products
The natural forests of Tanzania contain diversified tree species which can be used for timber. Some of these include Allanblackia stuhlmanii, Brachylaena huillensis, Cephalosphaera usambarensis, Dalbergia melanoxylon Juniperus procera, Milicia excelsa, Ocotea usambarensis, Olea capensis, Podocarpus usambarensis and Pterocarpus angolensis (Ruffo and Maliondo, 1990).
These indigenous tree species often have low growth rates and are widely scattered in the forest. In some areas, they have been so extensively logged that some species, both endemic and non endemic, are threatened to become extinct. Examples of threatened timber species in Tanzania are Allanblackia ulugurensis, Beilschmedia kweo, Brachylaena huillensis, Cephalosphaera usambarensis, Dalbergia melanoxylon, Englerodendron usambarensis, Entandrophragma excelsum, Isoberlinia scheffleri, Juniperus procera, Khaya nyasica, Milicia excelsa, Ocotea usambarensis, Podocarpus spp., Odyendea zimmermannii, Pterocarpus angolensis and P. mildebraedii (Ruffo and Maliondo, 1990).
In order to alleviate the pressure on natural forests, plantations were established using mainly exotic tree species such as Pinus patula, Cupressus lusitanica, Eucalyptus spp., Tectona grandis and Teminalia spp. By 1987, about 80 000 hectares of plantations had already been established in various parts of the country. Regardless of its small area coverage, plantation forestry accounts for about 600 000 m3 per year as compared to 300 000 m3 per year produced from indigenous hard wood natural forests.
Forests are a major source of wood used for building purposes, especially in rural areas in which most traditional houses are built using poles and withes. In research done by Zilihona et al. (1997), pole collection was among the leading forest uses by the local communities around the Udzungwa scarp forest reserve. In addition, fuelwood and charcoal are also leading products obtained from forests and woodlands. Rishard (1989) estimated a fuelwood consumption rate in Tanzania of about 36 million cubic meters per year.
Apart from timber, the forest provides a considerable amount of non-wood forest products (NWFPs) such as herbal medicines, food and fruits, latex and rubber, dyes and tannins, gum and resins, beverages and tonics as well as oil and perfumes. Other benefits include watershed management, maintenance of soil fertility, biodiversity conservation, CO2 sequestration, climatic amelioration, creation of employment and tourism.
2.3.1. Deforestation
2.3.2. Fires
2.3.3. Insect pests/pathogens
2.3.4. Seed procurement
2.3.5. Seed supply
The extent and diversity of forest ecosystems found in Tanzania create unique challenges in their management. Among the major problems facing forest conservation in Tanzania are listed bellow.
The high population growth rate of 2.8 percent, which demands more land for agriculture, settlement, grazing, wood extraction for building materials, charcoal and firewood, has been a major threat to the forest resources in Tanzania. About 130 000-500 000 hectares of forest lands are estimated to be cleared annually (MNRT, 1998).
Destruction of the forest by fire is increasingly threatening the future of miombo woodlands and closed forest ecosystems, causing severe destruction of vegetation and the environment as a whole.
Outbreaks of insect pests, particularly in plantation forests, have caused considerable damage to the forest. Canker diseases and pine woolly aphids have seriously affected the performance of Cupressus macrocapa and Pinus radiata in plantations to the extent of restricting future planting. In addition, Cupressus lusitanica has recently been attacked by insect pests identified as Cinara cupresiana. The named disease has caused a remarkable loss of cypress plantations in the country. About 15 000 hectares of C. lusitanica are reported to be under threat. In the natural forest, fungal infection has been a major threat to the survival of some tree species. Nsolomo and Venn (1996) reported a threat caused by heart rot on the survival of Ocotea usambarensis.
Tree seeds are mainly in two groups: orthodox and recalcitrant. The orthodox seed, which upon ripening and shedding, have relatively low moisture content (10-12 percent). On further drying to moisture content levels of around 4-5 percent, such seeds can be stored at 4°C for a very long period of time without serious loss in viability.
Recalcitrant seed, on the other hand, are shed from the mother tree with high moisture contents (40-70 percent) and, in nature, germination is immediate. They are intolerant to drying and also are temperature sensitive. Storage below 16°C generally kills them. A study at the National Tree Seed Programme (NTSP) shows that some recalcitrant seeds can hardly be stored for 1-4 weeks. Hence, long term storage for them at the NTSP is still a problem, as a good number of valuable species fall under this category. Species like Trichilia emetica, Azadirachta indica, Uapaka kirkiana, Sorindeia madagascariensis, Ximenia americana and Syzygium spp. are a few examples of recalcitrant seeds found in Tanzania.
The NTSP zonal seed Centres are mainly concentrated in the East. Communication has always been a problem in terms of seed inquiries, placing orders and receiving the seed. Consequently, people in the West of the country are forced to collect seeds locally which are of low quality and poor seedling survival.
On the other hand, the NTSP seed sources are well distributed in Tanzania. Some are in forest reserves and others in public lands. Seed in the reserve are well protected and managed, while those in public lands are threatened by human activities. It is common to find trees selected for seed source cut down and exploited for other uses, e.g. timber, fuelwood, construction poles, etc.
