IMPORTANT BIRD AREAS

Z006 Nyanga Mountains

SITE DESCRIPTION

The Nyanga Mountains form the northernmost extent of the Eastern Highlands in Zimbabwe. They lie c.70 km northeast of Mutare in two rural districts: Nyanga and Mutasa. The Nyangani Massif (2 592 m a.s.l.), a dolerite sill, is one of the few remaining areas in Zimbabwe of the ancient Gondwanaland erosion surface. The topography is very diverse, with a rolling hilly plateau in the west and north being the source of several large rivers, the Gairezi, Nyangombe and Pungwe. The plateau is deeply incised to the south by the gorges of the Pungwe and Nyazengu rivers. There are numerous spectacular waterfalls: the Mtarazi Waterfall, dropping some 380 m, is one of the highest in Africa. The eastern slopes of the mountains, particularly Nyangani Mountain, form a steep-sided escarpment, dropping down to the lowlands of the Honde Valley (900 m a.s.l.). The mountain’s western slope has an escarpment that drops from the peak at Rukotso (2 405 m a.s.l.) and World’s View to the Nyanga North Communal Land (1 400 m a.s.l.). The mean annual rainfall is extremely variable depending on local topography, but it ranges from c.3 000 mm p.a. at the highest altitudes to a low of c.1 200 mm p.a. at the lowest altitudes in the far west. The eastern slopes receive orographic rainfall and are frequently covered in mist. Above 1 800 m a.s.l. temperatures are cool and climate more temperate. Frost is common in winter. At lower altitude temperatures become more tropical, frequently exceeding 35°C. The eastern portion of the mountains adjoins the Honde Valley/Nyanga Lowlands (IBA Z007). The region’s soils are old, highly leached, coarse grained, sandy loams with low pH and nutrients. The mountains hold extensive high-altitude Afromontane grasslands (1 800-2 400 m a.s.l.). These grasslands form a microphyllous shrubland with a variety of herbaceous plants, including some Afro-alpine species. Afromontane rainforests are found on the eastern (windward) slopes and in ravines and kloofs on the leeward slopes. For the purposes of defining the borders of this IBA, the montane forest zone (above 1 650 m a.s.l.) is taken as the lower boundary. Syzygium masukuense is the dominant tree species in this undisturbed montane forest. Afrocrania volkensii montane forest occurs on wet boulder screes and in high valleys. These forests have affinities with those farther north in Malawi and East Africa. There are small patches of drier Widdringtonia nodiflora coniferous forest in fire-protected gullies. The west holds drier, flatter, grasslands interspersed with dwarf Brachystegia spiciformis woodland. Acacia abyssinica woodland occurs in isolated patches on colluvial soils at the base of granite kopjies. There are also extensive alien wattle (Acacia mearnsii and A. dealbata) and pine (Pinus patula) plantations and forests throughout the area.

BIRDS

Because of its popularity and accessibility, the Nyanga avifauna is relatively well known and includes 246 species. With respect to the globally threatened species, Nyanga’s grasslands hold very important numbers of breeding Blue Swallow Hirundo atrocaerulea. An unpublished field survey in the Nyanga National Park estimated the population to be at least 400 birds. Since there are areas of suitable habitat outside the Park, the total population could be 600 birds. Wattled Crane Bugeranus carunculatus breed in the National Park and on adjacent farms. Pallid Harrier Circus macrourus are occasional visitors, and Taita Falcon Falco fasciinucha, although seen rarely, probably breeds in the area. Nyanga holds two restricted-range species: Roberts’s Warbler Oreophilais robertsi and Chirinda Apalis Apalis chirindensis. Nyanga holds 14 of Zimbabwe’s 23 Afrotropical Highlands biome species. Species of the Zambezian and East African Coast biomes are also represented in the dwarf Brachystegia woodlands in the west.

OTHER THREATENED/ENDEMIC WILDLIFE

The extensive grasslands contain many herbs and shrubs with globally restricted/localised distributions. There are 6 plants endemic to these mountains and a further 6 species with very localised distributions that are near-endemic, including: Aloe inyangensis, A. rhodesiana, Moraea inyangani, Erica simii, Scadoxus pole-evansii, Dierama inyangensis, Euphoria citrina, E. crebifolia and Protea inyangensis. The special grassland species have biogeographical affinities with the South African Drakensberg flora. Many of these taxa reach their northernmost limit at the Nyanga Mountains. There are several endemic or restricted range amphibians, including: Inyanga Toad Vandijkophrynus inyangae, Probreviceps rhodesianus, Arthroleptis xenodactyloides, Leptopelis flavomaculatus, Afrixalus fornasinii and Hyperolius tuberilinguis. The Berg Adder, Bitis atropos, occurs in the montane grasslands. Samango Monkey Cercopithecus mitis and Blue Duiker Philantomba monticola are mammals restricted to the forests.

CONSERVATION ISSUES

The Nyanga National Park covers 440 km2, forming the core of the proposed Nyanga Mountains IBA and part of the adjacent

Nyanga Lowlands/Honde Valley (IBA Z007). The Park is surrounded by privately owned commercial farms, forestry plantations, tea estates and communal lands. The mountains are a popular tourist destination, attracting large numbers of local and international visitors. Much of the grassland and Afromontane forest lies within the Nyanga National Park. The greatest environmental threat to the Nyanga grasslands system, both inside and outside the National Park, is invasion by alien wattle and pine. An unpublished survey in 1988 showed that alien trees, which were spreading at an increasing rate, already impacted 40% of the National Park. Park authorities have not monitored this invasion, and the situation has certainly deteriorated. At present, most interested and affected parties do not fully recognise the extent and severity of the problem. The avifauna and other taxa are severely affected as the highly diverse grasslands change into sterile mono-specific stands of trees. The bird under greatest threat is the Blue Swallow. Alien trees severely alter ecological processes by changing local soil nutrients and pH balance and by causing decreases in ground water through excessive evapotranspiration. Their dramatic effect on landscape-level functioning and long-term perturbation of natural systems has been well documented elsewhere. Clear policy and action on the removal of invasive alien plants from these grasslands is urgently needed. High-altitude grasslands outside the Park, such as those at Rukotso, World’s View, Kwaraguza, Bende Gap, Nyafaru and Chingamwe, should be included in the Park, and their current low-priority conservation status improved. As fire is an important factor driving grassland functioning, research into its use as a management tool is urgently required.

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