Eastern Arc Mountains and Southern Rift

Biodiversity
Flagship Species
Threats
Conservation

Like scattered green islands within an ocean of brown, the Eastern Arc Mountains and those of the Southern Rift rise from the African savanna-woodland plains. These ancient mountain ranges run in a discontinuous chain from southern Kenya through Tanzania into Malawi and northern Mozambique. Most of the mountain blocks are composed of metamorphosed Pre-Cambrian basement rocks. However, two separate southern mountains have a different geology: Mt. Rungwe is formed from an ancient volcano, and Mt. Mulanje is the remnant of a giant plutonic intrusion. All the mountain blocks rise dramatically from the drier African Plateau, which is the product of hundreds of millions of years of erosion. Individual mountain blocks have been uplifted along ancient faults dating back to the breakup of Gondwana (more than 180 million years ago), with some uplift events occurring at least since the Miocene (about 30 million years ago), and especially over the last seven million years, associated with the development of the Rift Valley system (Griffiths 1993).

The Eastern Arc Mountains and Southern Rift region covers a total of 61 123 km², and is divided into two parts based on differences in the climatic regime. The Eastern Arc Mountains component is by far the biologically richer and, from north to south, includes the Taita Hills in Kenya, the North and South Pare, the East and West Usambaras, the Nguu, the North and South Ngurus, the Ukaguru, the Rubeho, the Uluguru, the Udzungwas, and Mahenge in Tanzania. There are also smaller isolated outliers including Kasigau in Kenya, and Mafi and Malundwe in Tanzania (Lovett 1988, 1990; Lovett and Pócs 1993; Lovett and Wasser 1993). The Southern Rift component is not under the stable Indian Ocean climatic regime and is biologically poorer. It also consists of several discontinuous mountain blocks and plateaus from the Ufipa Plateau and “Southern Highlands” of Tanzania, along the mountainous margins of Lake Malawi (Nyasa) to the Mulanje Massif in southern Malawi. The forests in Ufipa, such as Mbizi, exhibit strong Congolian and Albertine Rift influences in vegetation and in mammalian and invertebrate fauna, and are thus included in the Albertine Rift. The remaining part of the Ufipa Plateau is primarily montane grassland, more indicative of Southern Rift habitat (T. Davenport and A. Rogers, pers. comm.).

The Eastern Arc Mountains rise to 2 635 m at Kimhandu Peak in the Ulugurus and to a similar height at Mt. Luhomero in the Udzungwas, although more typically the maximum altitudes of different blocks are between 2 200 m and 2 500 m. The Arc Mountains are under the direct climatic influence of the Indian Ocean (Lovett 1990, 1993), and the climatic regime is believed to have been stable over millions of years, as indicated by biogeographical affinities to the forests of West Africa, Madagascar, and Asia (Hamilton 1982; Lovett and Friis 1996; Fjeldså and Lovett 1997; Lovett et al. 2004). The Eastern Arc Forests survived the driest and coldest periods of the last ice ages, as the Indian Ocean did not cool appreciably and rainfall patterns may not have been greatly disrupted (Lovett and Wasser 1993). Today, the climate in the mountains remains wetter, and less seasonal than the surrounding lowlands. The Ulugurus receive up to 3 000 mm rain a year on the eastern slopes, and annual rainfall on most other mountains exceeds 1 500 mm in wetter parts. There is, however, some evidence that the climate has become drier and more seasonal in recent decades, with a lower likelihood of the forests being enveloped in mist (Hamilton and Bensted-Smith 1989). Although the mountain soils are not rich, being old and leached, they are often better for agriculture than those of the surrounding lowlands. The favorable climate and moderate soils have attracted people to the mountains. As such, these areas support some of the highest population densities in Tanzania.

The eastern-facing slopes of the Arc Mountains are (or were) forest covered, but most blocks have plateaulike tops (e.g. Pares, West and East Usambaras, Udzungwas, and Ulugurus), the higher and colder of which support montane grasslands/heathlands. The forest formations of the Eastern Arc Mountains have been divided into upper montane (1 800–2 635 m), montane (1 250–1 800 m), submontane (800–1 250 m), and lowland (less than 800 m) (e.g., Pócs 1976). At the lowest altitudes (generally below 500–800 m, depending on the block), the forest grades into that more typical of the lowland Coastal Forests of Eastern Africa Hotspot. At higher altitudes the canopy height decreases, and at around 2 400 m altitude the forest generally grades into Afromontane grassland and heathland plant communities with temperate affinities (Lovett 1993). The upper altitudinal limit of forest vegetation is determined by the regular occurrence of frost, and varies between the different mountain blocks. The montane forest is characterized by large trees such as Ocotea usambarensis, Allanblackia stuhlmannii, A. ulugurensis, Ochna holstii, Podocarpus latifolius, P. falcatus, Ilex mitis, Cornus volkensii, Newtonia buchananii, and Synsepalum msolo. In the submontane forests, the timber trees Khaya anthotheca and Milicia excelsa also become important. Rubiaceae and Acanthaceae dominate the shrub and ground layers.

The Southern Rift is under the climatic influence of Lake Malawi (which is here considered part of the broader hotspot), with some southeast trade wind climatic elements from southern Africa (Chapman and White 1970). These climatic influences are more variable than those from the Indian Ocean. For example, climatic instability is indicated by dramatic fluctuations in the water levels of Lake Malawi, with major recessions before 25 000 years ago and 11 000 years ago, and further large falls 850–750 and 300–150 years ago (Owen et al. 1990).

Grasslands, commonly attributed to the high frequency and extent of fire, now dominate the natural habitats of the Southern Rift. Grass species include Loudetia simplex, Exotheca abyssinica, Monocymbium ceresiiforme, Themeda triandra, Andropogon spp., Pennisetum spp., and Setaria spp. (Kerfoot 1963). In areas of impeded drainage, permanent and seasonal bogs—dominated by grasses and sedges— have rich orchid floras (Kerfoot 1963; Cribb and Leedal 1982). The forests are mainly found in sheltered valleys and mountain ridges (White 1983; Dowsett-Lemaire 1989) and contain species such as Newtonia buchananii, Podocarpus latifolius, Ilex mitis, and Olea capensis, with Mt. Mulanje containing stands of the conifer Widdringtonia nodiflora and the endemic Mulanje cedar (W. whytei).

The Southern Rift Mountains mainly rise to between 1 400 and 2 400 m in altitude, but Mt. Rungwe and Mt. Mtorwi in Tanzania attain 2 961 m, and Mt. Mulanje in Malawi reaches 3 002 m. Many of the mountain blocks have plateau-like tops, such as the Ufipa and Nyika plateaus. The climate regime of these mountains is largely dictated by Lake Malawi, and for the northwestern areas (Ufipa Plateau), by Lake Tanganyika. Average annual rainfall ranges from 820 mm at Ufipa to over 2 800 mm in the Livingstone and Poroto mountains of Tanzania. The mean rainfall of the Malawian Mountains is around 1 500 mm. At the highest altitudes, temperatures as low as minus 7°C have been recorded, and frosts are common.

The isolated Mt. Namuli and neighboring formations in Mozambique have a somewhat ambiguous relationship with the Eastern Arc Mountains and the Southern Rift regions. Although being under the Indian Ocean climatic regime, they are not known to possess particularly high rates of endemism. The Southern Rift also has similarities to the mountains of the border between Zimbabwe and Mozambique —including Chimanimani and Gorongosa (here considered as a southern outlier of the Southern Rift component). The ancient, complex biological relationships between these different areas is illustrated by the plant Necepsia castaneifolia, which has subspecies in the Eastern Arc Mountains at Kimboza; a subspecies in Chirinda, southeast Zimbabwe; and two subspecies in Madagascar.

Biodiversity

The majority of the biodiversity of this region is concentrated in the Eastern Arc Mountains, from the Taita Hills in Kenya to the Udzungwa Mountains of Tanzania (Rodgers and Homewood 1982a, b; Lovett and Wasser 1993; Burgess et al. 1998; Newmark 2002), an area that is globally exceptional in terms of its levels of endemism (Brooks et al. 2002; Burgess et al., in press).

Current estimates suggest there are over 2 000 plant species in 800 genera in the Eastern Arc Mountains, of which at least 800 species (and probably well over 1 000) and around 40 genera are believed to be endemic (Lovett 1998b). There are also high rates of endemism in the non-vascular bryophytes, with 32 known endemics (Pócs 1998). Endemic plants are not only found in the forests, but also in the montane grasslands, wetland areas, on rocky outcrops, and in the drier “rainshadow” (west and north) areas. The Southern Rift supports at least 1 900 plant species, with 530 on Mt. Rungwe alone (T. Davenport, unpubl.). However, the levels of endemism are low, and perhaps only 100 plant species are endemic to the Southern Rift. Reduced endemism is most obvious in the forest flora, whereas the grasslands remain quite rich, especially for orchids and Protea. As examples, the Nyika Plateau supports 214 orchid species, with four endemic species and two endemic subspecies (Kurzweil 2000; Willis et al. 2000). The Kitulo Plateau in the Southern Highlands of Tanzania supports 350 plant species, three of which are strictly endemic (Lovett and Prins 1994; Davenport and Bytebier, in press). A few species of trees and large shrubs are also endemic to Mt. Mulanje, such as Widdringtonia whytei, Rawsonia burtt-davyi, Ficus modesta, and Encephalartos gratus (White et al. 2001). In total, we estimate that about 4 000 plant species in around 1 000 genera occur in the Eastern Arc and Southern Rift Mountains, of which perhaps 30% of the species and around 40 genera are endemic. Most of the endemics are in the Eastern Arc portion.

Among vertebrates, the highest endemism occurs in the amphibians and reptiles. Some 128 amphibian species are recorded, with 22 endemics, mainly in the Eastern Arc region, although four species are found only on Mt. Mulanje: Afrana johnstoni (EN), France's squeaker (Arthroleptis francei, EN), Broadley's ridged frog (Ptychadena broadleyi, EN), and Broadley's mountain frog (Nothophryne broadleyi, EN). The Eastern Arc Mountains are home to 50% of the members of the caecilian family Scolecomorphidae, among which the genus Scolecomorphus, with three species, is endemic. Besides Scolecomorphus, the Eastern Arc Mountains and Southern Rift are home to an additional seven endemic genera, among them Hoplophryne, Nectophrynoides, Probreviceps, Parhoplophryne, Nothophryne, and Callulina; the last three mentioned comprise single species. In 2002, a startling discovery was published from the Ukaguru Mountains: a large, brightly colored tree toad, Churamiti maridadi (CR), belonging to a new genus (Channing and Stanley 2002). New species continue to be discovered, and there are currently seven species of Nectophrynoides under description, while Callulina is in the process of being split into a number of species (S. Loader, pers. comm.).

Relatively high rates of endemism are also found in the other major groups of vertebrates. In the reptiles, of the 112 species known to occur in the Eastern Arc and Southern Rift Mountains, there are at least 36 endemic species, including eight species of chameleons (six Chamaeleo and two Rhampholeon), three species of worm snakes (Typhlops), and six species of colubrid snakes in four genera. Almost all of these are found in the Eastern Arc Mountains, where endemism is particularly high for an African mountain system (as cool and moist habitats are not ideal for exothermic reptiles). Mt. Mulanje also has a number of endemics, including the Mulanje mountain chameleon (Bradypodion mulanjense), Malawi stumptail chameleon (Rhampholeon platyceps), king dwarf gecko (Lygodactylus rex), and Mitchell's flat lizard (Platysaurus mitchelli).

The Eastern Arc and Southern Rift Mountains (as far South as Mt. Mulanje) are considered to be a single Endemic Bird Area (EBA) by BirdLife International (Stattersfield et al. 1998). Of the 639 species known from this region, 31 are endemic. Four endemic genera (Xenoperdix, Sceptomycter, Modulatrix, and Swynnertonia) also occur. Some bird species have extremely limited distributions; for example, the Taita thrush (Turdus helleri, CR) and Usambara akalat (Sheppardia montana, CR) occur only in a few square kilometers of forest in the Taita Hills and West Usambaras, respectively. In addition, the Uluguru bush-shrike (Malaconotus alius, EN) is confined to one forest reserve on the Uluguru Mountains, of less than 100 km² total forest area (Burgess et al. 2001). Some bird species have disjunct distribution patterns covering parts of the Eastern Arc, the Southern Rift, and the Zimbabwe Highlands; for example, the monotypic genus Swynnertonia and the long-billed tailorbird (Orthotomus moreaui).

Mammal endemism is also quite high, with 12 of 204 species endemic, among these three species of primates—the Sanje mangabey (Cercocebus sanjei, EN), the Udzungwa red colobus (Procolobus gordonorum, VU), and the mountain dwarf galago (Galagoides orinus)—, the black-and-red bush squirrel (Paraxerus lucifer), and six shrew species; the desperate shrew (Crocidura desperata, CR), for example, is known only from the Udzungwa and Rungwe Mountains. Further south, Vincent's bush squirrel (P. vincenti, VU) is confined to Mt. Namuli in Mozambique. A number of new mammal species have been discovered recently, or are in the process of being described, including a possible new species of dwarf galago (Galagoides sp.) on the Taita Hills (Perkin et al. 2003).

The region contains the very distinctive and highly endemic fish assemblage of the Lake Malawi Basin, as well as fishes from upland areas of rivers draining into the east African coast. Loach catfishes (Amphiliidae), shellears (Kneriidae), minnows (Cyprinidae), and other current-loving species tend to dominate the steep mountain streams in Tanzania, but they have few endemic species. In fact, only one of the 90-odd fish species and 38 genera occurring in Tanzania, Oreochromis chungruruensis, is endemic and lives in Lake Chungruru, a crater lake in the Rungwe Mountains, north of Lake Malawi (Trewavas 1983). In contrast, Lake Malawi has over 380 fish species, and nearly 90% of them are endemic. In addition to these cichlids, there are at least 12 large endemic catfishes of the genus Bathyclarias that live in deeper areas of the lake.

The Eastern Arc Mountains also support an invertebrate fauna that is exceptionally rich in endemic species, although it remains poorly known. Information on spiders and millipedes indicate that up to 80% of invertebrate species (and many genera) may be strictly endemic to a single mountain (Scharff 1992; Hoffman 1993). These patterns seem to be repeated across other invertebrate groups, including butterflies (De Jong and Congdon 1993). There are 78 butterfly species endemic to the Eastern Arc (Congdon et al. 2001). In the Southern Highlands, at least seven butterfly species are restricted to the Nyika Plateau in northern Malawi, whereas in Tanzania, Neocoenyra petersi is restricted to the Kitulo Plateau. Among the Odonata, there are two strictly endemic species in the East Usambaras (Clausnitzer 2001): the Mulanje damselfly (Oreocnemis phoenix) is an endemic species and genus to Mulanje and the dragonfly Teinobasis malawiensis is known only from montane streams in northern Malawi (Stuart et al. 1990).

Finally, although here considered as a distant outlier of the Southern Rift, the Chimanimani Mountains and Mt. Gorongosa area along the Zimbabwe-Mozambique border supports two endemic birds, Chirinda apalis (Apalis chirindensis) and Roberts' prinia (Prinia robertsi). As such, these mountains comprise their own Endemic Bird Area (Stattersfield et al. 1998). In addition, there at least two endemic mammals, Arend's golden mole (Carpitalpa arendsi) and the Selinda rock rat (Aethomys silindensis), and five endemic amphibians: the highland rain frog (Probreviceps rhodesianus, EN), cave squeaker (Schoutedenella troglodytes, CR), Inyanga frog (Afrana inyangae, EN), Inyanga toad (Bufo inyangae, EN), and Chirinda toad (Stephopaedes anotis, EN). Endemic reptiles include the ferocious round-headed worm lizard (Zygaspis ferox), Zimbabwe girdled lizard (Cordylus rhodesianus), FitzSimons' dwarf gecko (Lygodactylus bernardi), and Arnold's skink (Proscelotes arnoldi) in montane grasslands, and Marshall's dwarf chameleon (Rhampholeon marshalli) in montane forests. The region harbors 24 inland fish species, none of which are endemic, but the fish fauna is fairly distinctive, with relict populations of the loach catfish Amphilius uranoscopus and the shellear Kneria auriculata (Bell-Cross and Minshull 1988).

Flagship Species

As with the Coastal Forests of Eastern Africa Hotspot, traditional flagship mammals, such as the elephant (Loxodonta africana, EN), buffalo (Syncerus caffer), and leopard (Panthera pardus) are found in this region, mainly within Tanzania. However, as with the Coastal Forests of Eastern Africa Hotspot, the critical elements of biodiversity are smaller and less obvious, and mainly found in the plants, primates, smaller mammals, birds, and amphibians.

The Udzungwa red colobus has a restricted distribution in forests in the Udzungwa Mountains, where it survives in riverine, foothill, and montane forest patches. Although this colobus was once considered rare, a recent survey has estimated its total population at around 20 000 individuals (Dinesen et al. 2000). The Sanje mangabey was discovered in the early 1980s (Rodgers and Homewood 1982a), and is restricted to forests of the Udzungwas Massif from 300–1 600 m altitude. The most recent population estimate for this species is 2 500 individuals (Dinesen et al. 2000). Other notable mammal species include Abbott's duiker (Cephalophus spadix, VU), which is confined largely (although not entirely) to the montane parts of the Eastern Arc Mountains and the Southern Highlands in Tanzania, and the eastern tree hyrax (Dendrohyrax validus, VU), which also occurs in the Coastal Forests of Eastern Africa Hotspot. The near endemic black and rufous elephant shrew or sengi (Rhynchocyon petersi, EN) is also a notable mammal of the Eastern Arc Mountains.

Many of the endemic bird and chameleon species of the Eastern Arc Mountains also attract international attention. In the birds, attention focuses on the Udzungwa forest-partridge (Xenoperdix udzungwensis, EN), which is known from a few forests in the Udzungwa Mountains and one in the Rubeho Mountains; the Uluguru bush-shrike; and the rufous-winged sunbird (Nectarinia rufipennis, VU). The Nyika National Park on the Nyika Plateau in the Southern Rift supports the world's largest breeding population of blue swallow (Hirundo atrocaerulea, VU) (Dowsett-Lemaire et al. 2001), which breeds also on Mt. Rungwe, the Mbeya Range, and the Kitulo Plateau (T. Davenport, unpubl.).

Of the incredible diversity of amphibians, the genus Nectophrynoides requires particular mention, since it is endemic to the Tanzanian part of the Eastern Arc Mountains and Southern Rift and includes the majority of viviparous (live-bearing) frogs in the world (the only other confirmed viviparous frogs are two species endemic to Mt. Nimba in Liberia and Guinea). One of these species, the Kihansi spray toad (Nectophrynoides asperginis, CR), occurs only in the two-hectare spray zone of the Kihansi Falls in the Udzungwa Mountains (Poynton et al. 1998), where it has been affected by water diversion to the Kihansi Dam and populations may now be under 100 individuals (K. Howell, pers comm.). In addition, one other species, the Udzungwa Scarp viviparous toad (Nectophrynoides wendyae, CR), appears to be restricted to a tiny area of no more than nine hectares, on the Udzungwa Mountain escarpment.

Among plants, the best-known flagship species are the African violets (Saintpaulia spp.), with up to 20 endemic species in the Eastern Arc Mountains, and African primroses (Streptocarpus spp.), with 13 endemics. There are also at least 50 endemic species of balsam (Impatiens spp.) or “bizzy-Lizzy,” and a number of endemic begonias (Begonia spp.). Orchids, too, are charismatic, with more than 500 species in the Southern Rift (La Croix et al. 1991; Davenport and Bytebier, in press).

No discussion of flagships would be complete without mention of the amazing diversity of cichlid fishes in Lake Malawi. Many of these cichlids are strongly siteattached, rock-loving species known as mbuna, and are separated by large stretches of unsuitable sandy habitats that create ideal conditions for rapid allopatric speciation within the lake. Just small changes in body color, which is an important breeding characteristic in cichlids, can lead to isolated forms (Lowe-McConnell 1993).

Threats

During the colonial period, large areas of mountain forest and grassland were converted to commercial estates growing tea, coffee, and pine trees, or to cattle ranches (Rodgers 1993). More recently, areas of village forest and Forest Reserve have been cleared to establish banana, bean, and tree tomato farms to supply lowland cities with food —for example, in the Uluguru Mountains (Burgess et al. 2002) and the Nguru Mountains (N. Doggart, pers. comm.). Extensive cardamom plantations are still found beneath the canopy of forests in the East Usambaras. Natural montane grassland habitats are increasingly converted to crops such as beans, potatoes, and pyrethrum (Chapman and White 1970; Lovett and Prins 1994). Moreover, large areas of commercial softwood plantations have been established on former montane grasslands (for example, the 420-km² plantation at Sao Hill in Tanzania). The majority of grassland on Malawi's second largest plateau, the South Viphya, has been planted with exotic Pinus spp. (Dowsett-Lemaire 1989), and other areas of Malawi have been similarly afforested (Dowsett-Lemaire 1989; McKone and Walzem 1994).

Outside of protected areas (mainly Forest Reserves) and commercial estates, most land is used by villagers for subsistence agriculture. In Tanzania and Malawi, the mountains support high human population densities, which are often increasing both through high birth rates and immigration. Population densities of over 200 people/km² are common, and in the West Usambaras can exceed 400 people/km². The pressure for agricultural land from such high human densities is enormous, and occasionally forest areas have been lost. In one famous example, part of the Shume-Magamba Forest on the West Usambara Mountains was degazetted from a Forest Reserve soon after independence and was then converted to agriculture by landhungry residents (Lovett and Stuart 2001). Similarly, when local people realized in the early 1990s that part of the northern Uluguru Mountains was not within the forest reserve, it was rapidly deforested for banana plantations and subsistence agriculture (Burgess et al. 2002). An analysis of satellite images spanning 20 years up to 1989 showed that at least 24% of the Kitulo Plateau had been transformed by cultivation and pasture (Lovett and Prins 1994), a process that continues.

The Eastern Arc Mountains contain commercially valuable timber species such as Milicia excelsa, Khaya anthotheca, Beilschmedia kweo, Ocotea usambarensis, and Podocarpus spp. Many of these species have been logged on these mountains for more than a century, and in some parts of the region large specimens are commercially extinct. An infamous project in the East Usambara Mountains supported mechanical harvesting of timber, but caused much environmental damage and was stopped due to international outcry (Hamilton and Bensted-Smith 1989; Rodgers 1993). Today, most timber is extracted using pit-sawing techniques, where small groups of professional sawyers cut trees into planks on site and walk out of the forest carrying the sawn timber. This method is less damaging than mechanized logging, but allows all forest areas to be accessed. Almost all of this harvesting is illegal, as logging is banned in the Eastern Arc forests, but it supplies the local market with quality timber. It has proved difficult for the forestry authorities to eliminate this form of logging, and some claim that forestry authorities are themselves involved in the business.

People living on the slopes of the Eastern Arc Mountains and in nearby towns make use of many forest and grassland resources to augment their subsistence activities. A particularly important use of the forests is as a source of firewood for cooking and for heating during the cold season (Hymas 2000, 2001). Firewood harvesting may be the largest use of the Eastern Arc Mountain and Southern Rift forests, and one that is particularly hard to regulate. Other uses of the forests include being places for hunting, gathering medicinal plants, and traditional ceremonies —including burials (Mwikomeke et al. 1998; Shangali et al. 1998).

An important threat to the forest is the many fires started by people. The enhanced burning regime is believed to have been the main cause of the replacement of Afromontane forests with grassland and scrub-grassland across large areas (Dowsett-Lemaire 1989). Although there are laws to regulate the burning, there are also many local beliefs about the benefits of burning, which are hard to change.

Across different Eastern Arc Mountain blocks there are variable degrees of artisanal mining for gold, rubies, garnets and, formerly, on the Ulugurus, commercial mining of muscovite mica. Although most of these activities operate at a low level and have little impact, ruby mining has destroyed many parts of the Eastern Arc Mountains-Coastal Forest transition forests of Ruvu Forest Reserve in the Ulugurus. A recent gold rush has affected the East and West Usambaras and the Nguu Mountains. Thousands of people have flocked to these areas, causing considerable disruption to local villages and some forest destruction, mainly along streams.

The above factors have contributed greatly to the substantial loss of forest in the region. The Eastern Arc Mountains contain no more than 4 300 km² of forest habitat (less than 20% of an original extent of around 23 658 km² (Newmark 1998). The Udzungwas contain the largest area of natural forest (just over 1 800 km²). A number of mountains have lost at least 80% of their original forest cover, including Taita, Ukaguru, Mahenge, and West Usambara. The forests are also highly fragmented, with mean and median forest patch sizes estimated at 10 km² and 58 km², respectively (Newmark 1998). At the time that these figures were published, there were an estimated 94 forest patches in the Eastern Arc Mountains, many of which were already heavily degraded. The habitats of the Southern Rift portion originally covered around 37 465 km², but at least 70% of this area has been converted to agriculture or urban areas. In total, then, around 15 539 km² of original habitat remains, or around 25%.

There are also a number of threats that are impacting species directly. For example, a commercial trade in orchid tubers for food has developed in the Southern Rift, with the center of exploitation being northern Zambia, but now extending across the Southern Highlands of Tanzania, including Ufipa, the Kipengere Range, and the Kitulo Plateau. The trade in orchid tubers for consumption in Zambia is threatening as many as 85 terrestrial orchid species (Davenport and Ndangalasi 2003). Likewise, a new and recent threat to the amphibians of the region is the fungal disease chytridiomycosis, which has led to amphibian extinctions in Central and South America, and Australia. This disease has now been confirmed in the Udzungwa Mountains and in other parts of the Eastern Arc Mountains.

Conservation

Until now, the main mechanism for conservation in the Eastern Arc Mountains has been the establishment of protected areas under the management authority of different parts of the national government, with some smaller-scale efforts by private enterprise and local populations. In the Tanzanian portion of the Eastern Arc Mountains, there is one national park (Udzungwa Mountains National Park, gazetted in 1992; 1 900 km²); a small area of forest on Malundwe Hill, the only part of the Eastern Arc Mountains falling within Mikumi National Park; one government nature reserve (Amani Nature Reserve in the East Usambaras); one private nature reserve; a small research reserve owned by the University of Dar es Salaam at Mazumbai in the West Usambaras; and some forest within tea estate lands. The majority of the remaining forest in the region is within forest reserves. The central government controls the most important water catchment forests as national forest reserves, most of which are under the “catchment” project in the following Tanzanian Regions: Kilimanjaro (i.e., North and South Pare), Tanga (i.e., West and East Usambara, Nguru North), and Morogoro (i.e., Uluguru, Ukaguru, Nguru South, part of Rubeho and Udzungwa). National forest reserves in the Iringa region (Udzungwa Mountains) fall outside the “catchment” project, but are still managed for water catchment purposes by central government staff. There are also some “local authority forest reserves” managed by the district Natural Resource Offices, but they tend to be smaller and less important areas. The national forest reserves, especially those under the catchment project, are generally better protected than the local authority forests.

There are a few private forests, mainly on tea estates (e.g., Ambangulu Tea Estate in the West Usambaras and Brook Bond Estates in the Udzungwas), some of which are managed for conservation. Many small village forests also exist across the Eastern Arc. Several were traditionally burial forests, or land that the village was not using. With the development of the new land laws in Tanzania (1999) and the new Forest Act (2002), these areas can now be controlled at the village level, and many are in the process of being turned into village forest reserves.

The Eastern Arc Mountains provide the water sources for many of the large dams of Tanzania, and for hydropower facilities at Kihansi Gorge and Kidatu in the Udzungwas, and Pangani River in the Tanga Region. Kihansi Dam was built with World Bank funding, and has led to the near-extinction of the Kihansi spray toad due to drying up of its only known habitat (Lovett et al. 1997; Poynton et al. 1998; Quinn et al., in press). The Ruvu River, flowing from the Ulugurus, provides the principal water supply to the 3–4 million people of the capital city of Dar es Salaam, and for Morogoro. The water supplies for Mufindi, Iringa, Kilosa, Ifakara, Mpwapwa, Korogwe, Same, Lushoto, Muheza, and Tanga also originate in the Eastern Arc Mountains. The same rivers provide the water for large irrigated rice and sugarcane schemes, and for sisal estates and other kinds of farms. The value of these ecological services is not well quantified, but runs into hundreds of millions of dollars per annum. The Southern Highlands, meanwhile, contribute to four of the country's twelve main drainage basins and provide water to the majority of people in that part of Tanzania.

Tanzania is among the poorest nations in the world (World Bank 2002), and is being assisted to conserve the Eastern Arc forests by a number of international agencies. Significant World Bank funding is available to help build management capacity and develop a Forest Agency, and the World Bank has also provided $7 million to capitalize an Eastern Arc Endowment Fund. These investments became operational in 2003. The Global Environmental Facility-United Nations Development Programme (GEF-UNDP) is also investing in the development of a holistic conservation strategy for the Eastern Arc Mountains, bringing together biodiversity, water supply, economics, and poverty-alleviation elements. One of the aims of the project is to designate the Eastern Arc Mountains as a World Heritage Site. Other bilateral donors supporting conservation of the Arc are the Danish International Development Agency (DANIDA), Finnish International Development Agency (Global Finland), and the Norwegian Agency for Development Cooperation (NORAD), which is providing long-term support to “catchment” forest reserves. NGOs also actively pursue conservation in the region, in particular the Tanzania Forest Conservation Group, World Wide Fund for Nature, and the Wildlife Conservation Society of Tanzania. In 2004, the Critical Ecosystem Partnership Fund approved a $7-million investment strategy that will provide significant funding for research and conservation within the former Eastern Arc Mountains and Coastal Forests Hotspot.

Likewise, the governments and populations of the countries of the Southern Rift are all impoverished, and hence international efforts are needed to assist with the conservation of these mountains. Many of the mountain blocks in Tanzania are heavily populated and used for agriculture, with most remaining natural vegetation confined to government-proclaimed and traditional reserves (McKone and Walzem 1994; McKone 1995). For example, the Mbeya region of Tanzania's Southern Highlands contains 17 forest reserves. A number of other forest reserves lie within the administrative regions of Rukwa and Iringa. These generally have low levels of enforcement and are often subject to illegal pit-sawing, fuelwood collection, grazing, agriculture, hunting, and uncontrolled burning. Besides these official forest reserves, there are numerous smaller traditional reserves in the Southern Highlands, established by local communities for a variety of cultural reasons. The Government of Tanzania announced in February 2002 that 13 500 ha of Kitulo Plateau will be gazetted as a new national park, significantly increasing protection for endemic plants, particularly the threatened orchid flora (Davenport, 2002).

The Wildlife Conservation Society (WCS) is assisting the Tanzania Forest Department and the Tanzanian National Parks with conservation work in the Tanzanian portion of the Southern Rift. WCS has a long-term conservation site in the Southern Highlands, working on research, forest and grassland management, community conservation, education, and tree planting on Mt. Rungwe, Kitulo, and other key sites.

The protected area network of Malawi is regarded as inadequate. Part of the Nyika Plateau is protected in the Nyika National Park of Malawi and Zambia. Part of Chipata Mountain is protected in Malawi's Nkhotakota Game Reserve (Carter 1987), while Chirobwe Mountain in the Dedza-Chirobwe Highlands has a forest reserve, although this is under pressure from wood collectors. Deforestation is particularly pronounced in Malawi. As rural population densities are very high, all that remains of the once extensive mid-altitude montane forests are small relictual groves used as graveyards by local people (Dowsett-Lemaire 1989). Further south, Mt. Mulanje is mainly protected as forest reserves with some forest remaining within tea estates on the mountain. The GEF is working to improve conservation in Mt. Mulanje, and WCS has recently begun work on biodiversity research and monitoring.

In the southern outlier along the border between Zimbabwe and Mozambique, the higher-altitude vegetation types are relatively well protected, in particular by the Chimanimani National Park (171 km²) and the Nyanga National Park (440 km²). The Mozambique side of the Chimanimani Mountains is less protected, and Mt. Gorongosa and Mt. Namuli are presently unprotected. Zimbabwe was until recently able to manage well its natural resources, but this has declined dramatically over the past few years, and the current situation is unclear. In Mozambique, the IUCN has assisted the government in re-establishing the infrastructure of its protected areas following the end of hostilities in 1992, and progress continues to be made.

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