The Taita Hills lie in south-eastern Kenya, south and west of Voi town, and rise abruptly above the semi-arid plains of Tsavo West National Park (IBA KE025). These plains, at c.600–700 m altitude, isolate the hills from other mountains and highland blocks. The closest of these are the Chyulu Hills (KE028) and North Pares, c.70 km away, and Mount Kilimanjaro, c.80 km away. The West Usambara mountains, with which the Taita Hills share some botanical affinities, are c.120 km distant. The Taita Hills are divided into three main blocks. Sagalla Hill (peak 1,450 m), directly south of Voi, is separated from the rest of the hills by the Voi river on the plains. The main body of the hills, Dabida, lies 25 km north-west of Voi, including the high peaks of Ngangao (2,149 m) and Vuria (2,228 m). To the north-east of this range lies the massif of Mbololo (2,209 m), separated from the main block by a valley at c.900 m. Some 50 km to the south-east, and not included within this IBA, lies Mount Kasigau. The forest on this isolated peak has biogeographical affinities with the Taita Hills, but its fauna and flora are as yet little studied. Geologically, the hills are the northernmost outpost of the ancient Eastern Arc mountains of Tanzania and Malawi. At the base of the hills, rainfall is only c.600 mm/year. This rises to c.1,300 mm on the top, with local variation. Dry bushland runs up the flanks of the hills, giving way rather abruptly near the top to smallholder cultivation and remnant patches of moist forest. The area is heavily settled. The total population is around 250,000, and densities reach 1,400 people/km2 in places. Cultivation is intensive, with maize the most conspicuous crop. As a result of the high human pressure on land, forest remains only as scattered fragments on the hilltops and ridges. Sagalla retains only c.3 ha of moist forest and Mbololo c.220 ha along the hill crest, while the main block has a number of tiny remnants, including Fururu (12 ha), Mwachora (4 ha), Macha (3 ha), Ngerenyi (3 ha), Kichuchenyi (2 ha), Yale (2 ha) and Vuria (1 ha), and two larger patches: Chawia (c.50 ha) and Ngangao (c.92 ha) (areas based on mapping carried out in 1997). Wundanyi County Council has approved the gazettement of all these sites as Forest Reserves for many years. However, while a number of smaller patches (including plantation forest) have been gazetted, the main blocks of Sagalla, Chawia, Ngangao and Mbololo (though managed by the Forest Department) still have not. All the forests have been logged over for valuable timber trees, and substantial portions have been planted with exotic conifers. Ocotea spp. were once common in the forests, but have been almost entirely logged out. Other characteristic trees are Tabernaemontana stapfiana and Maesa lanceolata (growing especially where the forest has been heavily disturbed), Albizia gummifera, Chrysophyllum gorungosanum, Cola greenwayi, Macaranga conglomerata, Newtonia buchananii, Syzygium sclerophyllum, Xymalos monospora and the palm Phoenix reclinata. The Taita Hills forests have been isolated for a long time from other moist forests, and have themselves been fragmented for at least a century. Forest loss since the 1960s has been very substantial, with estimates of 99% for Vuria, 95% for Sagalla, 85% for Chawia, 50% for Ngangao and under 50% for Mbololo. Despite their small size, the forests are important for water catchment (supplying the Voi river and various local streams) and for soil conservation.
See Box and Table 2 for key species. The Taita Hills are treated as part of the Tanzania–Malawi mountains Endemic Bird Area, but they share no restricted-range bird species with the other sites in this EBA. In fact, their avifauna is generally more closely related to that of the Kenyan mountains EBA (109), with which they share the restricted-range Cinnyricinclus femoralis. The birds include an element from the northern Tanzanian highlands, for instance through the presence of Andropadus milanjensis (also on the Chyulu Hills), the race helleri of Pogonocichla stellata, the race otomitra of Zoothera gurneyi, and Phylloscopus ruficapilla. There is also a coastal element (mainly at the lower-elevation Sagalla), with four of Kenya’s 29 East African Coast biome species present. The avifauna is generally impoverished compared to larger, less isolated blocks of forest: only 14 out of the 70 Afrotropical Highlands biome species regularly occur. However the forests are important for a number of globally threatened species, namely Falco fasciinucha (known only from early specimens collected at the base of these hills); Turdus helleri (a Taita forests endemic and forest-specialist presently known from Mbololo, Ngangao, Chawia and Yale; total population estimated as c.1,350 birds, of which 78% are in Mbololo); Zosterops silvanus (a Taita forests endemic, but the most adaptable of the three, recorded at most forest patches apart from Sagalla; total population in the Taita Hills estimated as 1,500 birds, with an additional 5,600 on nearby Mount Kasigau); Apalis fuscigularis (a Taita forests endemic, but only recorded on the main massif, in Ngangao, Chawia, Fururu and Vuria, and scarce everywhere); Cinnyricinclus femoralis (up to 20 recorded at Chawia; may be an overlooked seasonal visitor); and Circaetus fasciolatus (one record from Chawia). Regionally threatened species include Hieraaetus ayresii and Stephanoaetus coronatus, although their current status is unknown.
Non-bird biodiversity: Levels of endemism in the Taita Hills are generally very high, reflecting the forests’ long isolation. There is an endemic snake Amblyodipsas teitana, an endemic caecilian Afrocaecilia taitana, an endemic toad Bufo teitensis, and two frogs that are otherwise confined to the Usambaras (in the Eastern Arc mountains of Tanzania). Three butterflies, Cymothoe teita, Charaxes xiphares desmondi and Papilio desmondi teita, are endemic to these forests and their fringes. At least nine plant species are endemic, including the trees Coffea fadenii, Psychotria crassipetala, Memecylon teitense and Zimmermania ovata; an undescribed Psychotria may already be extinct. The plant Saintpaulia taitensis has a global range of about 0.5 ha on Mbololo. Another 26 plant species are endemic to the Eastern Arc forests.
Pressure/threats to key biodiversity
The tiny size of the Taita Hills forests, and the dense human population surrounding them, makes them extremely vulnerable. Most of the fragments are already heavily disturbed. The largest and least accessible, Mbololo, is also the most intact; Ngangao has suffered substantial damage; and in the small fragments, almost all the large-circumference trees have been cut. Chawia is still losing its small and easily cut trees. This disturbance is having a particularly negative effect on Turdus helleri. It is already absent from all but one of the small fragments, and its population density in Chawia is only a quarter, and in Ngangao a half, that in Mbololo. The population in Chawia is heavily male-biased, has high levels of fluctuating asymmetry and shows evidence of a recent genetic bottleneck. The biodiversity importance of the forests is still little appreciated by their custodians. Conservation of these unique forests will require integrated planning and action. Several initial steps are obvious. Those forests that have not yet been gazetted, should be, as strict nature reserves under the Forests Act. Even this status may not afford adequate protection. Kenyan law presently lacks provision for small nature reserves to be designated for their biodiversity importance. The draft new Museums Bill, yet to be presented to Parliament, allows such sites to be gazetted as National Monuments. If this legislation comes into force, the Taita Hills forests would be an obvious place to apply it. Plantations of exotic trees, mainly conifers, make up a substantial area of all the major fragments. These plantations appear to be performing poorly. However, indigenous vegetation is regenerating underneath the canopy. Controlled felling that allows gradual natural forest regrowth could eventually increase the indigenous forest area substantially. However, it is clear that the increasing demand from the surrounding population for fuelwood, poles and other forest products simply cannot be met sustainably from the natural forests. Strict control of forest use is needed, combined with agro-forestry extension programmes to help people meet these needs on-farm. Extraction of medicinal plants and bark might still be possible under a careful license system. Some compensation for the loss of forest products might come from the development of ecotourism in the Taita Hills. The hills are accessible and conveniently located near the main Nairobi–Mombasa road. They are scenic, and offer spectacular views from many places, the forests have much to interest any naturalist (and certainly any birdwatcher), and are easy and safe to walk in. Sites like Ngangao and Chawia could be sensitively developed for visitors, with walking trails, information boards, trained local guides and accommodation at campsites or in local guesthouses. Such an approach has been successful elsewhere in the world. The East African Wildlife Society is running a community-based conservation project that should eventually give rise to an integrated conservation plan. This links with a regional GEF project focusing on cross-border biodiversity: the Taita Hills is one of its focal sites. A programme of research into the forest’s biodiversity and the effects of fragmentation, run jointly by the National Museums of Kenya, Kenyatta University and the University of Antwerp, was completed in 2000 and has produced a number of management recommendations. However, nothing may happen with the necessary urgency unless decision-makers at all levels are convinced 0>of the exceptional importance of these sites.