The United Republic of Tanzania is located in East Africa between longitude 29° and 41° East and latitude 1° and 12° South. It covers a total of 947,600 km2. Tanzania mainland accounts for 945,100 km2 (99.74% of the area) while the islands of Zanzibar (Unguja and Pemba) account for the remaining 2,500 km2 (0.26%). Tanzania mainland is endowed with a wide range of natural resources as well as ecological and cultural diversity including extensive areas of arable land, wildlife reserves and parks, mountains, forests, rivers, and lakes.
The forests in Tanzania mainland are high in biodiversity. The country contains over 10,000 plant species (See Tree Species List for Tanzania), hundreds of which are nationally endemic. Of the plant species, 305 are identified as threatened in the IUCN Red List, with 276 species classified as Endangered. The main forest types include deciduous miombo woodlands in the western, central and southern parts of the country, Acacia-Commiphora woodlands in the northern regions, coastal forests and woodland mosaics in the east, mangrove forests along the coast of the Indian Ocean, and closed canopy forests, which grow on the ancient mountains of the Eastern Arc, along the Albertine Rift close to Lake Tanganyika in the west, and on the younger volcanic mountains in the north and central parts of the country. Woodlands are mostly open and often degraded with undergrowth of grass and shrubs. Woodlands are subject to frequent grass fires stemming from adjacent human activity such as agriculture.
Many different types of forest resources are to be found in Tanzania. However, the forests are divided into four broad categories which are Closed forests, Woodlands, Mangroves and Plantations
1. Closed forests:
The closed forests are divided into montane/submontane closed forest and lowland closed forest. The prevailing types are the high- altitude rain forests, occurring in scattered formations on mountain slopes in areas with abundant precipitation and short dry seasons. These highland closed forests are mainly found at Mt. Kilimanjaro, Mt. Meru, in the Usambaras, the Ulugurus, the Uzungwas. When relatively undisturbed, such moist forests can consist of several more or less distinct layers (trees of different species /maximum heights). Some of these forest areas are almost permanently cloaked in mist (“Nebelwald”). The montane/submontane closed forests are again divided into four subcategories, characterized by certain dominant species:
- Ocotea-Podocarpus forest (occurring at Mt. Kilimanjaro, W. Usambara, and, without Ocotea Usambarensis, on Mt. Meru, in the Mbulu Highlands etc.)
- Juniperus forest (Mt. Meru, Mt. Kilimanjaro, W. Usambara, on drier part facing slopes)
- Bamboo thicket (Mt. Meru, Mt. Rungwe, Iringa Highlands, Ulugurus etc.)
- Cassipourea forest (Mt. Meru, Uzungwa etc.)
The lowland closed forests are often consisting of low- growing stands of semidecidous trees and can be found on the lower slopes of mountains, merging into higher-altitude rainforest in the Ulugurus, the Ngurus, the Usambaras etc.
Lowland Bamboo occur in clumps in miombo woodland. It also occurs as “groundwater forest” (in areas with a very high groundwater table, as in the Kilombero Valley, and “gallery forest” (closed forest along rivers and watercourses). The term “closed forest” in itself refers to the merging tree canopies, creating a high degree of cover in comparison with the woodlands.
More than ninety percent of Tanzania’s forested area is covered by savanna woodland. The woodlands show a varying degree of tree cover, and many terms are used to make according distinctions, such as “closed woodland”, “open woodland” and “wooded grassland”. A common term for most woodland is “miombo woodland”. “Miombo” is a name used by the Wanyamwezi people for the Brachystegia trees so very common in the woodlands, often being dominant or co-dominant with species such as Julbernardia and Acacia. The miombo woodlands usually features more or less scattered trees of low stature (12-18 m.), and the ground is covered with grasses, herbs and (often thorny) scrubs. These woodlands occupy terrains from almost sea- level to 1600 metres above sea-level with annual rainfalls between 500 and 1200 mm. and one rainy season mostly. They are widespread on Tanzania’s central plateau and are part of a greater “miombo zone” in eastern and southern Africa. Tree species of the miombo woodlands are fire resistant to some degree, and fires occur frequently either induced by humans or naturally. Termite mounds are often found in valleys in the miombo woodlands, harbouring a more succulent vegetation of trees such as Pterocarpus and dalbergia presumably due to a higher level of nutrients in the soil created by the insect activity.
3. Mangroves & coastal forests:
Mangrove forests that cover about 150,000ha occur along the coastline of Tanzania, on the islands and in river deltas such as the Rufiji delta that harbours the greatest concentration of mangrove in Tanzania. The mangrove trees thrive in swampy conditions; their roots are immersed in salt water. “Coastal forest” seems to be a recent term not to be found in the classification systems. Perhaps it should be placed under “closed forests” rather than here? - it is described as “...evergreen or largely evergreen closed canopy vegetation >8 m. tall ... forming part of the Zanzibar-Inhambane regional mosaic ... subject to a monsoonal climatic regime, and growing on Mesozoic or post-Mesozoic rocks generally within 50 km. of the coast and below 600 m. altitude ... all mangrove - dominated vegetation and deciduos woodland is excluded”.
Approximately 700,000 ha. of the Tanzanian forests resources are plantations, mostly for industrial use. The central government own and manages 24 plantations with about 500,000ha while the private companies and individuals owns about 200,000ha. The greater part of the plantations are stocked with softwoods, mainly pines, but also cypress. The preferred hardwoods are teak and eucalyptus. None of these trees are indigenous. Most of these plantations are located in humid mountaneous areas, such as the Sao Hill plantation at Mufindi, which is by far the country’s largest plantation. There are black wattle plantations for tannin extraction in Njombe and rubber tree plantations in Morogoro and Tanga regions. Some small plantations/woodlots for fuelwood use also exist.