The Udzungwa mountains are the south-western block of a chain of ancient mountains stretching from south-central to north-east Tanzania and the extreme south of Kenya. Much of the upper plateau has been cleared of forest and is now degraded grassland or farmland. This site includes all of the major forest areas outside of the National Park (TZ011). The most important forest blocks for bird conservation are Udzungwa Scarp (20,220 ha), Kisinga-Rugaro (14,164 ha) and West Kilombero Forest Reserves (now c.55,000 ha, following the establishment of Udzungwa National Park). The highest peak, Luhombero at 2,576 m, is within the Udzungwa National Park. Nyumbenitu (2,284 m) is the next-highest peak in the northern highland block while Nyamerenge (at 2,284 m) dominates the high ground immediately to the east of Iringa. These two areas are separated by the Lukosi river valley which runs north to join the Ruaha. Sawala (2,072 m) is the highest point in the south of the range while Selegu (2,454 m) dominates the rather isolated forest block on Image mountain, where much timber was logged in the 1970s and 1980s and most of what is left is second-growth thickets.South-west of the Udzungwa range lie the escarpment forests of the Kipengeres and remaining patches around Njombe. To the north, the Uvidundas are virtually continuous with the Udzungwas, separated only by the steep-sided valley of the Ruaha river. The highland plateau in the Udzungwa mountains slopes gently to the west, grading through stunted miombo woodland and grassland to the dry country around Iringa which is an extension of the Somali–Masai Acacia–Commiphora bushland habitat.
See Box and Tables 2 and 3 for key species. The Forest Reserves of this IBA contain far higher densities of such birds as Schoutedenapus myoptilus, Modulatrix orostruthus, Alethe fuelleborni, Sheppardia sharpei, Cossypha anomala, Modulatrix stictigula, Cisticola nigriloris, Orthotomus metopias and Ploceus bertrandi than any other comparable area. There is likely to be some interchange of species such as Cossypha natalensis and Cercotrichas quadrivirgata between the forest along the foot of the Udzungwa escaprment and the coastal forests. The number of range-restricted species is highest in the eastern part of the IBA.
Non-bird biodiversity: The Udzungwa mountains contain many Eastern Arc endemics. Elephant Loxodonta africana (EN) occurs in the escarpment forests; these may be animals moving between forest habitats and the open grasslands and swamps of the Kilombero valley. The poorly known primate Galago orinus (DD) occurs, and a new species Galago zanzibaricus udzungwensis (LR/nt), was recently named from Matundu Forest Reserve, while the endemic Cercocebus galeritus sanjei (EN) occurs along the southern escarpment of the Udzungwa mountains, and Procolobus gordonorum (VU) is widespread with large populations in some forests. The ungulate Cephalophus spadix (VU) is rare, but this is an important stronghold for this species. A small isolated population of rhino Diceros bicornis (CR) in the northern Great Ruaha river basin moves up into Image Forest in the dry season.
Pressure/threats to key biodiversity
Most of the forests are important for water catchment as well as for biodiversity conservation. Evidence suggests that the forest cover in this area has been broadly maintained over recent decades. Nonetheless, illegal logging and pole-cutting continue inside some Forest Reserves. Deforestation also continues outside the Forest Reserves and the National Park. Hunting of elephant, buffalo and hippopotamus occurs. The short-term effects of land clearance for projects such as the Kihansi Hydro-power Scheme are unlikely to be detrimental. However, the long-term effects of immigration of workers and their families will create demands for forest products beyond the resources that remain outside the Forest Reserves.