The Nguu mountains are the northernmost extension of the central Eastern Arc mountains. They are highly dissected by numerous streams that all drain eastwards towards the Indian Ocean. The valleys are well-settled at low densities and most of the lowland forest was removed in the early twentieth century. The nine Catchment Forest Reserves listed represent virtually all the montane forest cover in these mountains and include significant amounts of lowland forest, especially on the wetter eastern slopes: Derema Catchment Forest Reserve (CFR) (3,928 ha), Kilindi CFR (4,299 ha), Kwediboma CFR (285 ha), Mbwegere CFR (368 ha), Mkongo CFR (985 ha), Mkuli CFR (2,931 ha), Nguru North CFR (14,042 ha), Pumila CFR (1,062 ha) and Rudewa CFR (556 ha). The forests hold populations of rare, near-endemic trees such as Psychotria tanganyicensis and Sloetiopsis usambarensis in Kilindi and Amorphophallus stuhlmannii and Memecylon schliebenni in Nguru North. West and north of these mountains the vegetation is of the Somali–Masai type while to the east it is lowland woodland of the Zanzibar–Inhambane coastal zone. The valleys have the northernmost Brachystegia woodlands in eastern Tanzania.
See Box and Tables 2 and 3 for key species. The avifauna of the Nguus is more closely related to the Ngurus and Ukagurus than the Usambaras, which lie only 100 km to the north-east. Apart from a visit to some of the lower-altitude woodlands during 1991, the only records available are from a 1995 university expedition to Nguru North CFR, which discovered the only known montane population of Sheppardia gunningi in Tanzania. Other nominally lowland forest birds recorded include Circaetus fasciolatus, Neocossyphus rufus, Dicrurus ludwigii and Ploceus bicolor. In addition, five species of the Zambezian biome have been recorded from this site (see Table 3).
Non-bird biodiversity: The ungulate Cephalophus harveyi (LR/cd) has been recorded. Many of the trees restricted to the Eastern Arc mountains occur and Pterygota mildbraedii is only known in Tanzania from the Nguus.
Pressure/threats to key biodiversity
Many of the forests in the Nguus were logged commercially in colonial times. More recently, excessive illegal timber extraction and repeated pole-cutting of potentially valuable trees has delayed the forests’ ability to regenerate. Much conservation emphasis is placed on boundary clearing and planting with fast-growing exotics. However, local people are rarely to blame for illegal extraction of commercial timber and are generally well aware of the forest boundary. Establishment of new Forest Reserves for the planting of fast-growing indigenous species to produce timber, fuel and food for local people may be the only long-term answer.