Southern Miombo woodlands
Spread over a considerable portion of southern Africa, the Southern Miombo woodlands ecoregion is distributed in several areas across the Central African Plateau. It covers central and northern Zimbabwe and extends into Mozambique, southern Zambia and Malawi. The landscape is somewhat level or gently undulating, with numerous inselberg formations. Miombo woodland mixes with mopane as well as smaller wetlands to provide habitat for a wide variety of animals, including endangered and charismatic mammals such as African Elephant (Loxodonta africana) and Black Rhino (Diceros bicornis). While a number of protected areas fall within this ecoregion, management and resources are sometimes lacking. Poaching of ivory and rhino horn remains a persistent conservation threat.
Location and general description
This ecoregion is disjunct in distribution and consists of four main parts, separated at least partially by the drainage systems of Zimbabwe and Zambia. The largest section covers most of Zimbabwe, and spills over into Mozambique on the eastern side of the Chimanimani Mountain Range. Zambezian Mopane woodland surrounds most of this area and separates this block from the second largest section of the Southern Miombo woodland ecoregion. North of the Zambezi Valley, this portion extends over the southern third of Zambia, as well as into the western parts of Malawi and northern Tete province in Mozambique. To the north and northwest of this ecoregion, the vegetation mostly gives way to Central Zambezian Miombo woodland. The remaining smaller segments are located in southern Mozambique, narrowly separated by the Rio Save and bordering White’s Zanzibar-Inhambane regional mosaic to the east. To the west, mopane and undifferentiated woodland of the Zambezian Mopane woodland ecoregion predominates.
Most of the ecoregion is found on the Central African Plateau at elevations ranging between 1000 and 1500 metres (m). Although the area is characterized by flat or undulating plains, intrusive granites and gneisses dominate geologically, and frequently rise up above the woodland as rounded hills (also known as dwalas) or inselbergs. Numerous grassy wetlands are interspersed along drainage lines in vleis or dambos. Highly weathered, acidic, and nutrient-poor soils, mainly alfisols and some oxisols in wetter locations, predominate and are more than three metres deep in places. Shallow stony soils are common along the escarpment and around inselbergs. Soils are generally well-drained. To the west, the ecoregion extends marginally onto aeolian Kalahari sands. The sections of the ecoregion in Mozambique are found at much lower elevations, from 200 to 800 m, and are mostly on sedimentary Karoo Sandstones.
The ecoregion generally experiences a tropical savanna climate with three distinct seasons: a hot dry season from mid-August through October; a hot wet season from November through March; and a warm dry season from April through early August. Mean maximum temperatures range between 18°C and 27°C, but are typically around 24°C. The ecoregion experiences mean minimum temperatures between 9°C and 15°C, and is virtually frost-free. Temperatures are considerably higher in the lowland areas of the ecoregion. Rainfall is highly seasonal, with a marked austral winter drought usually lasting from four to seven months. The mean annual rainfall is approximately 600 to 800 millimeters (mm) in the main part of the ecoregion in Zimbabwe and increases to about 1000 mm in the lower-elevation portion in Mozambique.
Floristically, this ecoregion forms part of a wide belt of miombo woodland that stretches from Angola in the west to Tanzania in the east. This miombo belt is virtually synonymous with the Zambezian Phytochorion, the largest of White’s Regional Centers of Endemism within Africa. Miombo plant communities are dominated by trees belonging to the family Caesalpiniaceae, and characterized by species in the genera Brachystegia and Julbernardia.
This ecoregion, mapped by White as drier Zambezian miombo, is floristically impoverished, although areas of serpentine soils in imbabwe provide localized sites of speciation and endemism. Msasa (Brachystegia spiciformis) and Mnondo (Julbernardia globiflora) predominate. Other commonly found tree species include Uapaca kirkiana, Brachystegia boehmii, Pale-fruited Monotes (Monotes glaber), Willow Beechwood (Faurea saligna), F. speciosa, Velvet Bushwillow (Combretum molle), Purple-leaved Albizia (Albizia antunesiana), Spiny Monkey-Orange (Strychnos spinosa), Corky Monkey-orange (S. cocculoides), Governor's Plum (Flacourtia indica), and Velvet Wild Medlar (Vangueria infausta). Grass cover in the Southern Miombo woodlands is typically sparse.
A number of vegetation communities are found within the Southern Miombo woodlands. Where drainage is poor, Acacia savannas or grassland may become locally dominant. Other associated vegetation includes dry deciduous forest and thicket, as well as deciduous riparian vegetation.
The human population of this ecoregion is fairly high, and the area includes the cities of Harare and Lusaka (the capitals of Zimbabwe and Zambia, respectively). While a large number of people live in urban centers, an estimated 73 percent of the Zimbabwean population live in rural areas and rely on subsistence farming as a livelihood. Population densities are between 50 and 200 persons per square kilometre for most of the area, falling to fewer than 50 persons to the west and in Mozambique to perhaps fewer than 20 persons per square kilometre, although data reliability is not deemed to be high.
Biodiversity features
The overall faunal diversity of this ecoregion is fairly high, as many of its species overlap with surrounding miombo and savanna ecoregions. Annual droughts can last up to seven months and fires are frequent. As a result, many species are at least seasonally dependent on non-miombo sites within or adjacent to the ecoregion to provide food, water or shelter. These non-miombo refuges also provide a greater variety of [[habitat]s], resulting in higher richness in ecotonal areas within the ecoregion, such as near inselbergs or rivers, than in areas of uniform miombo woodland.
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While miombo woodland in general provides important habitat for many large animals, the ecoregion does not support high densities of mammals per unit area, probably due to the seasonally arid conditions and poor soil, and hence forage quality. Several threatened animals occur in this ecoregion, including the critically endangered Black Rhino (Diceros bicornis) and the endangered African Elephant (Loxodonta africana). Although the ecoregion does not support these globally endangered animals in very large numbers, it is still important habitat because both species are known to have potentially large home ranges and utilize miombo habitat. Of the 50,000 to 60,000 African Elephants thought to occur in Zimbabwe, roughly 27,000 animals are concentrated in mopane woodland that borders this ecoregion. Until around the year 2000, these areas supported the largest population of Black Rhino in Africa (about 2200). White Rhino (Ceratotherium simum) are also known to inhabit the region and are classified as Lower Risk by the IUCN Red List.
The overall paucity of large animals in this ecoregion favors the Roan Antelope (Hippotragus equinus), one of the mammals largely restricted to this habitat type, as it prefers habitats that have few competitors or carnivores . Other ungulates typical of this ecoregion include Sable Antelope (H. niger), Lichtenstein’s Hartebeest (Sigmoceros lichtensteinii), Southern Reedbuck (Redunca arundinum), Greater Kudu (Tragelaphus strepsiceros), Eland (Taurotragus oryx), and Cape Buffalo (Syncerus caffer). Topi (Damaliscus lunatus) are also known to occur in the ecoregion.
Most of the ungulates characteristic of miombo woodland are specialized grazers that selectively feed on nutrient-rich, actively growing grass shoots. This means that they require large foraging areas, as they often have to move seasonally through the landscape in search of suitable fodder. For example, sable antelope remain within miombo woodland for much of the rainy season (October to May), but move out during the dry season. Many of these ungulates also rely on ecotones or non-miombo habitat within the ecoregion. For example, Lichtenstein’s Hartebeest prefers the ecotone between miombo and dambos, while the Southern Reedbuck is most often found in rank grass valleys and glades within miombo woodland.
Large carnivores characteristic of the region include Lion (Panthera leo), Leopard (P. pardus), Cheetah (Acinonyx jubatus), Spotted Hyena (Crocuta crocuta), and the endangered Painted Hunting Dog (Lycaon pictus). Smaller predators include Caracal (Caracal caracal), Side-striped Jackal (Canis adustus) as well as the Selouse Meerkat (Paracynictis selousi), which is a rather narrow range-restricted species.
Of the nearly 500 bird species found in the area, none are strictly endemic. However, six species are either largely confined to the ecoregion or have extremely small distribution ranges. Lilian’s Lovebird (Agapornis lilianae), chiefly inhabits mopane woodland in the Zambezi Valley, but seasonally moves into more mixed woodland on alluvial terraces. The Boulder Chat (Pinarornis plumosus) is found in well-wooded terrain with large boulders. Stierling’s Woodpecker (Dendropicos stierlingi) is confined to two small areas of southern Malawi with the remainder of the population restricted to the Eastern Miombo Woodland ecoregion, while Chaplin’s Barbet (Lybius chaplini), endemic to south-central Zambia, is a locally common resident of miombo woodland. The latter species is classified as Lower Risk/Near Threatened by Birdlife International. The Pink-throated Twinspot (Hypargos margaritatus) and the Lemon-breasted Canary (Serinus citrinipectus) have restricted ranges and utilize miombo woodland, although their main ranges fall outside this ecoregion. Three globally threatened species are also found in this ecoregion, including two vulnerable species, the Cape Vulture (Gyps coprotheres) and the Lesser Kestrel (Falco naumanni), as well as the lower risk Taita Falcon (Falco fasciinucha), which is threatened by pesticide use in northern Zimbabwe.
A number of amphibian associates are found within the ecoregion,including the Beira Toad (P. beiranus), African clawed toad (Xenopus laevis), African ornate frog (Hildebrandtia ornata), Boettger’s metal frog (Cacosternum boettgeri), Common reed frog (Hyperolius viridiflavus), and the Lukula grass frog (Ptychodena taenioscellus). - See more at: http://www.eoearth.org/article/Zambezian_flooded_grasslands?topic=49597#gen1Reptiles are the only faunal group with high levels of endemism in this ecoregion, with 30 species of snakes and lizards predominantly or exclusively found in the South Miombo woodlands. However only four species are strict endemics: Regal Girdled Lizard (Cordylus warreni regius), Dwarf Wolf Snake (Lycophidium nanus), and the Chimanimani Flat Lizard (Platysaurus ocellatus).
A number of amphibian associates are found within the ecoregion,including the African Split-skin Toad (Schismaderma carens), Benguella Reed Frog (Hyperolius benguellensis), Rough Sand Frog (Tomopterna tuberculosa), African Clawed Toad (Xenopus laevis), Grey Foam-nest Treefrog (Chiromantis xerampelina), Angola River Frog (Amietia angolensis), African Ornate Frog (Hildebrandtia ornata), Boettger’s Metal Frog (Cacosternum boettgeri), Common Reed Frog (Hyperolius viridiflavus), and the Mababe Reed Frog (Phrynobatrachus mababiensis).
Ecoregion conservation status
Historically, miombo vegetation was relatively underpopulated, partially due to poor soils, which made it unsuitable for cultivation. The great rinderpest epidemic of the late nineteenth century further contributed to the depopulation of both people and livestock in the area. This allowed thick woodland vegetation to grow, which provided ideal habitat for the proliferation of Tsetse Flies (an insect of the genus Glossina that causes livestock and human sleeping sickness). Since the Tsetse Fly does not affect wildlife, and the area is sparsely populated, miombo provides excellent habitat for game parks. Dry savannas (which include miombo habitat) are today one of the most extensively protected vegetation types in southern Africa. However, in recent years miombo has been facing increasing pressure due to human population expansion and activities. Aside from protected areas, there is relatively little intact miombo remaining.
Zimbabwe, which contains the largest contiguous section of the ecoregion, is internationally known for its organized conservation effort. It is also responsible for having spearheaded community-based conservation in southern Africa through the CAMPFIRE Program. About 13 percent of Zimbabwe’s total land area is protected. Zambia’s protected areas cover 32 percent of the country, although most of these areas fall into the Central Miombo woodland ecoregion. These areas have suffered from insufficient management in the past, and continue to endure widespread deforestation due to slash-and-burn practices of native peoples.
Although there are only three official Zambian protected areas that fall into the ecoregion, Game Management Areas (GMAs) cover most of the remaining area of in the Zambian portion of this ecoregion. North Luangwa National Park, bounded by the Muchinga Escarpment in the west and the Luangwa River in the east, is mostly covered by miombo vegetation, with some open grassland on the floodplain. Lukusuzi National Park is found in the eastern watershed area of the Luangwa River. Almost half the park consists of plateau where miombo is dominant, although grassland is also found on the plateau and along rivers. Both parks have an abundance of wildlife representative of the ecoregion. The expansive Lower Zambezi National Park lies on the northern bank of the Zambezi River. Miombo vegetation covers the slopes while mopane and acacia dominate in the valley. A wide variety of game occurs in the area, although poaching has drastically reduced Black Rhino and African Elephant populations.
The miombo regions of Zimbabwe support a large number of small protected areas, many of which are found in rugged wilderness terrain. These parks and reserves include Chizarira National Park, Chirisa Safari Area, Matusadona National Park, and Mavuradonha Safari Area, which are all found in the north regions of the country. Other smaller parks such as Nyanga National Park, Mazowe Botanical Reserve, Sebakwe, Robert McLlwaine, Lake Kyle, and Ngezi Recreational Parks are much more accessible, as they are close to main transport routes or major towns, but do not harbor significant populations of charismatic large mammals. Private wildlife conservancies are becoming more numerous in Zimbabwe, offering consumptive and non-consumptive safaris.
Mozambique, having suffered severe political and military upheavals through years of civil war, does not presently have any effectively managed areas. Almost all wildlife was exterminated over the years for meat and to finance the warfare. Some management plans and efforts are, however, beginning to be reapplied to Gorongosa National Park, a protected area that falls into the ecoregion.
Threats to the ecoregion
A large proportion of this miombo ecoregion has been completely transformed. Outside protected areas, some of the most immediate threats result from expanding cultivation, commercial logging, overgrazing, rapid human population growth, and too-frequent fires, partially due to intensive slash and burn farming. Although habitat is fairly well conserved in protected areas, even national parks are affected by indigenous people who increasingly encroach onto protected land to search for fuel, wood, or new grazing or farming areas. Poaching, especially of Black rhinos and African Elephants, is a continuing problem and has resulted in severe losses of animals, despite extensive protection efforts. According to government figures, Zimbabwe may have lost as much as 80 percent of its Black Rhino population due to poaching in 1992 alone. The current political and economic situation in Zimbabwe poses a threat to the extensive system of protected areas, and land invasions threaten the private wildlife conservancies.
The large-scale cultivation of cash crops, such as maize, wheat, and especially tobacco, has seen a huge conversion of miombo into agricultural land. In the case of tobacco, growing this export crop has led to large losses of woodland, both for land and fuelwood. These losses are increased by a need for fresh land each year to avoid risk of root-knot nematodes, as well as for the curing of tobacco, which is presently often carried out using charcoal. Several wildlife species are perceived as pests by farmers and are frequently eliminated on private lands. For example, livestock farmers have eradicated the African wild dog from large areas, while the aardvark is routinely exterminated on agricultural land. Leopards are typically persecuted by livestock farmers as well, although that situation may change in some locales where trophy hunts are allowed.
Expanding rural human populations and the subsistence use of resources place substantial ecological strain on the ecoregion. More than 80 percent of the people living in miombo depend on fuelwood for cooking, heat, and light, and grazing pressures of communal livestock populations are considerable, especially in Zimbabwe. Hunting for bushmeat was once conducted primarily for subsistence and cultural traditions. Now, the bushmeat trade is becoming commercialized and urbanized, often catering to the urban market. Other species are used for traditional medicine. For example, the scales of the ground pangolin (Manis temminckii) are used as love charms.
Justification of ecoregion delineation
This ecoregion is comprised of White’s ‘drier Zambezian miombo woodland’ to the southwest of Lake Malawi, and includes several other areas east of the Zimbabwe Highlands, west of Lake Malawi, and southeast of Lake Kariba due to similar vegetation compositions.
This ecoregion is part of larger complex of Caesalpinoid woodland ecoregions that support wet and dry miombo, mopane, thicket, dry forests, Baikiaea woodland, and flooded grassland habitats, among others. The dominance of Caesalpinoid trees is a defining feature of this bioregion (i.e., a complex of biogeographically related ecoregions). Major habitat types (e.g., mopane and miombo) and the geographic separation of populations of large mammals are used to discriminate ecoregions within this larger region. All of these ecoregions contain habitats that differ from their assigned biome or defining habitat type. For example, patches of dry forest occur within larger landscapes of miombo woodlands in several areas. More detailed biogeographic analyses should map the less dominant habitat types that occur within the larger ecoregions.
References
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