The East Usambara mountains comprise a steeply scarred plateau on which the main ridges run from north to south. At less than 130,000 ha, they are one of the smallest mountain ranges in Tanzania and are separated from the much larger West Usambara mountains (TZ071), to the north-west, by the wide Lwengera river valley, which flows south to join the Pangani river. The mountains themselves are drained by the catchment of the Sigi river, entering the Indian Ocean at Tanga. The forest of the range became fragmented some time ago, first by clearance for coffee plantations and latterly by tea plantations. Some of the better-quality lowland forest has been replaced with plantations of teak Tectonia grandis. The 19 main Forest Reserves are in the process of being reorganized into larger blocks, with the inclusion of important lowland forest that has survived on public land. The Amani Forest Nature Reserve was set up in May 1997.Although the mountains are not particularly high, since they are situated within 35 km of the coast they receive typically 2,000 mm of rain annually, spread across all months. Submontane forest exists at lower altitudes in the East Usambara than any other comparable mountain block in Tanzania. There are also areas of lowland forest in the East Usambaras. Some 12,916 ha of submontane forest and 29,497 ha of lowland forest are included in the IBA. To the north of the highland block there are extensive areas of Brachylaena woodland.
See Box and Tables 2 and 3 for key species. The East Usambara mountains are one of the most important sites on the African mainland for the conservation of globally threatened birds. Bubo vosseleri, Otus ireneae, Orthotomus moreaui, Modulatrix orostruthus, Swynnertonia swynnertoni and Ploceus nicolli all occur here. The endemic races Hyliota australis usambarae and Spermophaga ruficapilla cana occur at low densities in only a few localities. Other important species in an East African context are such forest-edge specialists as Indicator meliphilus and Lonchura fringilloides, while Campethera mombassica is locally common. Bostrychia olivacea is seen rarely.
Non-bird biodiversity: There are many endemic and near-endemic species in these forests. Seven plants (African violets) Saintpaulia species are endemic. About 3% of the plants in the East Usambaras are strict endemics, and 22% are near-endemics. Some 15 species of amphibia and 13 reptiles occur that are endemic to Tanzania. About 85% of the millipedes are endemic, 45% of the molluscs, and 40% of the butterflies. The mammals Cephalophus spadix (VU), Rhynchocyon petersi (EN) and Myonycteris relicta (VU) all occur.
Pressure/threats to key biodiversity
Amani Nature Reserve is Tanzania’s first official forest Nature Reserve. Commercial logging in the early 1980s damaged much of the remaining forest. This has now ceased. The lowland forest is arguably now most at risk. The commercial growing of cardamom Elettaria cardamomum inside the Forest Reserves is also a major problem. The expansion of the tea industry and an increase in the use of inorganic fertilizers creates concerns for long-term damage to the soils and water. There have been significant changes in precipitation within the East Usambara range. Data from the 1930s suggest there was then a shorter dry season and far more cloud cover than is usual today. Some forests have been affected by the invasion of the tree Maesopsis eminii. This tree is a native of north-western Tanzania and has caused considerable problems throughout the East Usambaras. Eradication has been considered although recent research suggests that indigenous trees are regenerating well under Maesopsis and that, given time, may out-compete it.The East Usambara Catchment Forestry Project offers a long-term future for these forests. There are also small-scale NGO conservation initiatives being developed, working with village communities. With so many defunct sisal estates between the East Usambaras and the sea there is an opportunity to plant them with indigenous hardwoods.
BirdLife International (2021) Important Bird Areas factsheet: East Usambara Mountains. Downloaded from
http://www.birdlife.org on 19/10/2021.