Eastern Arc Mountains and Coastal Forests of Tanzania and Kenya ...

The degree of faunal endemism in the Eastern Arc Mountains varies widely across taxa. Sixpercent of mammals, 3 percent of birds, 68 percent of forest-dependent reptiles, 63 percent offorest-dependent amphibians, 39 percent of butterflies and 82 percent of linyphiid spiders areendemic (GEF 2002). Some of these species have extremely limited distributions. The Kihansispray toad, described in 1998, is found in an area of less than 1 km 2 (Poynton et al. 1998). Threeendemic bird taxa (variously described as full species or subspecies) are restricted to the 6 km 2of forest in the Taita Hills (Brooks et al. 1998). Records for the Udzungwa partridge areconfined to two localities in the Udzungwas and one in Rubeho (Baker & Baker 2002). Amongstsome invertebrates (linyphiid spiders, opilionids and carabid beetles), single site endemismexceeds 80 percent (Scharff et al. 1981; Scharff 1992, 1993; Burgess et al. 1998).Using a subset of 239 species endemic and near-endemic to the Eastern Arc Mountains, the EastUsambaras emerge as the most important site in terms of numbers of endemics, while theUlugurus rank top for density of endemics (Burgess et al. 2001). As expected, the big forestblocks (Usambaras, Ulugurus and Udzungwas) are more species-rich than the smaller blocks(e.g., North Pare, South Pare, Ukaguru and Mahenge). Most of the endemic taxa are not onlyforest dependent; they are dependent on primary forest. The low-elevation forests are rich inendemics and total numbers of species, but are very limited in overall area, having sufferedextensive clearance for agriculture. The uniqueness of the biodiversity in the Eastern ArcMountains is attributable to both relictual and recently evolved species (Burgess et al. 1998c;Roy et al. 1997). Biogeographical affinities indicate ancient connections to Madagascar (45species of bryophytes shared) (Pocs 1998), West Africa (many birds and plant genera) (Lovett1998b; Burgess et al. 1998c) and even Southeast Asia (where close relatives of the Udzungwaforest partridge and the African tailorbird are found) (Dinesen et al. 1994).Biodiversity in the Coastal ForestsThe pattern of endemism in the Coastal Forest Mosaic is complex, reflecting the wide range ofhabitats and heterogeneous forest types, a high degree of turnover of local species betweenadjacent forest patches and many disjunct distributions (Burgess 2000; WWF-US 2003b). Theecoregion, which includes the islands of Zanzibar and Pemba, is a mosaic of forest patches,savanna woodlands, bushlands, thickets and farmland. The highest biodiversity is found in thevarious kinds of closed canopy forest vegetation: dry forest, scrub forest, Brachystegia(miombo) forest, riverine forest, groundwater forest, swamp forest and coastal/afromontanetransition forest (Clarke 2000; WWF-US 2003b). Closed canopy forests, however, makes uponly 1 percent of the total area of the Coastal Forest Mosaic.Overall, there are more than 4,500 plant species and 1,050 plant genera (WWF-US 2003b), witharound 3,000 species and 750 genera occurring in forest. At least 400 plant species are endemicto the forest patches and about another 500 are endemic to the intervening habitats that make up99 percent of the ecoregion area (WWF-US 2003b). The majority of these species are woody butthere are also endemic climbers, shrubs, herbs, grasses and sedges (Clarke et al. 2000). Asubstantial proportion of the endemic plants are confined to a single forest (for example, RondoForest, Tanzania, has 60 strict endemics and Shimba Hills, Kenya, has 12) (Clarke et al. 2000).The flora as a whole has affinities with that of West Africa, suggesting an ancient connectionwith the Guineo-Congolian lowland forests (Lovett 1993). Endemism is primarily relictualrather than recently evolved (Clarke et al. 2000; Burgess et al. 1998c).Faunal endemism rates have been estimated for forest species in the Swahelian Regional Centreof Endemism (including the transition zone in Mozambique). These are highest in theinvertebrate groups such as millipedes (80 percent of all the forest species), molluscs (68percent) and forest butterflies (19 percent) (Burgess 2000). Amongst the vertebrates, 7 percentof forest mammals, 10 percent of forest birds, 57 percent of forest reptiles and 36 percent of12