Central Zambezian Miombo woodlands

Miombo woodland in bloom, central Malawi. Photograph by Judy Oglethorpe

Ecoregions (main)

Published: May 6, 2014, 1:43 pm

Author: World Wildlife Fund

Author: C. Michael Hogan

Topic Editor: Mark McGinley

Topics:

Ecoregions (main)

Conservation Biology (main)

Biogeography (main)

The Central Zambezian Miombo woodlands is one of the most sizable ecoregions in Africa, with limits ranging from Angola up to the shores of Lake Victoria in Tanzania. All the typical miombo flora are represented, but this region has a greater degree of floral richness than most miombo woodlands, with far more evergreen tree species than elsewhere in the miombo biome. The harsh dry season, long droughts, and nutrient deficient soils are ameliorated by the numerous wetlands interspersed throughout the ecoregion, covering up to thirty percent of the region’s total area. As a result, a diverse assemblage of fauna occurs here, from Sitatunga (swamp-dwelling antelopes), to Chimpanzees, in the internationally noted Gombe Stream Reserve. The birdlife is also exceptionally rich, as is the fauna of some amphibian groups. The ecoregion contains areas of near-wilderness with exceptionally low human populations and extensive protected areas. Other parts of the ecoregion, typically close to lakes and mountains, have higher population densities and the miombo habitat is much more degraded. Bushmeat hunting by native peoples, dryland agriculture, deforestation (especially by slash and burn for charcoal production near larger population centres), and mining are increasing threats in the ecoregion.

Location and General Description

The Central Zambezian Miombo woodlands ecoregion covers approximately 70 percent of the land area of central and northern Zambia; the southeastern third of the Democratic Republic of Congo (DRC); western Malawi, much of Tanzania; and parts of Burundi and northeastern Angola. Consisting mainly of broadleaf, deciduous savannas and woodlands, it is characteristically interspersed with edaphic grassland and semi-aquatic vegetation as well as areas of evergreen groundwater forest To the east, the ecoregion gives way to drier Eastern Miombo woodlands and to the northeast to the spiny Southern Acacia-Commiphora bushlands and thickets. South of the ecoregion, Zambezian and mopane woodlands and Southern miombo woodlands predominate. Angolan miombo and edaphic generated, secondary grassland on Kalahari Sands are dominant in the west and northwest, while the more tropical conditions of White’s (1983) Guineo-Congolian Region present the ecoregion to the north.

Hippopotami bathing in river, Katavi NP. @ C. Michael Hogan

Predominantly confined to the Central African Plateau, most of the ecoregion is drained by the Zaire and Zambezi River basins to the north and south, respectively. Elevations characteristically range between 800 and 1200 meters. There are localized areas of higher relief, such as Mount Mulumbe in southern Democratic Republic of Congo, which rises to an upland plateau at approximately 1500 meters. Much of the ecoregion consists of flat plains or rolling hills covered by extensive woodland, although rocky outcrops and inselbergs are fairly common. The gentle warping of the plateau surface has caused ponding (via seasonal flooding) in many places, giving rise to a large number of lakes and wetland areas, such as Lake Bangweulu and the Upper Kafue Basins. Many smaller wetlands or dambos are scattered throughout the ecoregion and can cover up to thirty percent of the landscape. Precambrian volcanic, granitic, serpentine, and sandstone rocks form the underlying geology. The combination of these crystalline rocks, low relief, moist climate and warm temperatures has produced highly weathered soils that are commonly more than three meters deep. The soils are typically well-drained, highly leached, nutrient-poor and tend to be acidic, with a low proportion of organic matter. Oxisols predominate in higher rainfall areas, but give way to ultisols to the south and east as average annual rainfall declines. Locally, patches of altisols are also found, particularly associated with wetland areas.

The Central Miombo experiences a seasonal tropical climate. Most of its rainfall is concentrated during the hot summer months of November through March or April. This is followed by a pronounced winter drought, which can last up to seven months. Mean maximum temperatures are typically around 27°C although they are markedly warmer (around 30°C) at lower elevations. Areas of higher elevation such as central Zambia experience average maximum temperatures of around 24°C. Mean minimum temperatures range from 9° to 18°C. The area receives 1000 to 1200 millimeters (mm) rainfall annually, with figures as high as 1400 mm recorded at higher elevations in the southeast, decreasing towards the east and north of the ecoregion.

Miombo woodlands form the dense forest woodland that bisects Africa directly south of the Congo Basin and East African savannas. They are dominated by trees of the subfamily Caesalpinioideae, particularly species belonging to the genera Brachystegia, Julbernardia, and Isoberlinia, which seldom occur outside miombo. In this ecoregion, mature miombo woodland trees are usually 15 to 20 meters tall, with a broadleaf shrub and grass understory beneath. Although trees in this area are primarily deciduous, this area has a much higher proportion of evergreen trees than drier Zambezian miombo, about 24 percent compared to nine percent in the Zimbabwean woodlands. Rich in species, this ecoregion - mapped as wetter Zambezian miombo woodland by White (1983) - includes nearly all the miombo dominants, such as Brachystegia floribunda, B. glaberrima, B. taxifolia, B. wangermeeana, Marquesia macroura, Julbernadia globiflora, J. paniculata, and Isoberlinia angolensis.

Fire is an important ecological factor in miombo woodland. The strong seasonality in precipitation leaves the vegetation dry for several months of the year, and thunderstorms at the start of the rainy season can easily set the vegetation afire. However, in addition to being naturally fire-prone, miombo is frequently burned by indigenous people to clear land for cultivation, to maintain pastures for livestock, or in accordance with traditional beliefs (e.g. concerning rainmaking or social status).

The human population of this ecoregion is generally fairly low except in Malawi and Burundi, which in 1997 were estimated to support an average of 230 and 86 people per km² respectively. The low population densities in most of the ecoregion are largely due to: (1) the nutrient-poor soils that limit agricultural potential; (2) the widespread presence of tsetse fly (Glossina spp.); and (3) vectors of trypanosomiasis, which affects humans as well as domestic livestock. Historically, the threat of this disease prevented humans from bringing cattle into many areas. However, pockets of high-density populations are found in areas that have access to permanent water, such as along the margins of Lake Tanganyika and Lake Malawi as well as the Copperbelt in northern Zambia and southern DRC.

Biodiversity Features

The Central Miombo has a high degree of floral richness when compared to the other miombo ecoregions. Although miombo as a whole has a fairly low degree of generic endemism – sharing many species with the Sudanian and coastal formations – species richness and localized endemism is high in many herbaceous plant genera such as Crotalaria and Indigofera. Furthermore, this ecoregion is the center of endemism for the Brachystegia genus with 17 of its 35 species located in Zambia.

Rates of faunal endemism vary greatly between taxonomic groups. Mammalian endemism is restricted to four species of rodents, namely Monard’s dormouse (Graphiurus monardi), Rosevear's striped grass mouse (Lemniscomys roseveari), and two white-toothed shrews, Crocidura ansellorum (CR) and C. zimmeri (VU), with the last two being strict endemics. D'Anchieta's fruit bat (Plerotes anchietae, DD), a range-restricted species of conservation concern is also found in the area.

Warthog (Phacochoerus africanus). (Photograph by David Olson)

As with the other miombo ecoregions, Central Miombo does not support large animals in high densities, although due to the vast size of the ecoregion, its overall importance for such species is very high. The low large-mammal density is attributed chiefly to the harsh dry season, long droughts and the poor soils, which generally support only vegetation of low nutritional value. These conditions tend to favor low numbers of large-bodied animals, such as the endangered African elephant (Loxodonta africana) and critically endangered Black rhino (Diceros bicornis), as well as African buffalo (Syncerus caffer), which are able to survive on poor quality forage by consuming large quantities of plant material. Specialised grazers are also common. They selectively feed on growing high-quality grass shoots, often making use of a range of non-miombo habitats throughout the year. Such specialists include sable antelope (Hippotragus niger), roan antelope (H. equinus), Lichtenstein’s hartebeest (Alcelaphus buselaphus lichtensteini), and Southern reedbuck (Redunca arundinum), all species largely restricted to the miombo belt, as well as Eland (Taurotragus oryx), and Greater kudu (T. strepsiceros). Many species make use of the wooded margins or open areas of the numerous grassy floodplains and swamps scattered through the ecoregion. Lechwes (Kobus leche), Puku (K. vardoni), Tsessebe (Damaliscus lunatus), Oribi (Ourebia ourebi), Blue wildebeest (Connochaetes gnou) and sitatunga (Tragelaphus spekii), are antelope that prefer open grasslands, seasonally flooded or marshy habitat. Waterbuck (K. ellipsiprymnus), bushbuck (Tragelaphus scriptus), and blue duiker (Cephalophus monticola) are mostly found in more wooded areas close to permanent water. Other large ungulates include zebra (Equus burchelli) and giraffe (Giraffa camelopardalis). Hippopotamus (Hippopotamus amphibius) are relatively common to the ecoregion, for example there is a population of 2000 to 3000 in Mweru-Marsh National Park in northeast Zambia.

Large carnivores characteristic to the region include lion (Panthera leo), leopard (P. pardus), cheetah (Acinonyx jubatus), spotted hyena (Crocuta crocuta), striped hyena (Hyaena hyaena), the endangered African wild dog (Lycaon pictus) and side-striped jackal (Canis adustus). Smaller predators include caracal (Caracal caracal), miombo genet (Genetta angolensis), as well as African golden cat (Profelis aurata), which periodically wanders into the ecoregion from its preferred moist forest habitat in the DRC.

Masai giraffe browsing at Katavi NP. @ C. Michael Hogan

Due to its proximity to the true rainforest habitats of the DRC and Uganda, this ecoregion supports a significant number of primates, mostly on its western margins and where it grades into sub-montane forest habitats. The Gombe Stream Game Reserve, although largely covered by evergreen forests, protects substantial miombo habitat on its lower slopes. Well-known as the site of Jane Goodall’s long-term study of the endangered chimpanzee (Pan troglodytes) this area also supports species such as red colobus (Procolobus pennantii), and black and white colobus (Colobus angolensis), blue monkey (Cercopithecus mitis), and red-tailed monkey (C. ascanius). More widespread primates that are typical of the open miombo formations are vervet monkey (Chlorocebus aethiops) and baboon (Papio hamadryas).

The birdlife in the ecoregion is particularly rich in species. However, rates of endemism are low with the only strict endemics being Ruwet’s masked weaver (Ploceus ruweti, DD) and black-faced waxbill (Estrilda nigriloris, DD), the last two both being restricted to southern DRC. Ruwet’s masked weaver is known only from the swamps bordering Lake Tshangalele/Lufira in southern DRC, while the black-faced waxbill, is found only around the Lualaba River and Lake Upemba. Other range-restricted species include grey-crested helmetshrike (Prionops poliolophus), an uncommon species endemic to the woodlands of Kenya and northern Tanzania, noted as worthy of monitoring by Collar and Stuart (1985). Although Lilian’s lovebird (Agapornis lilianae) tends to avoid miombo, several isolated populations are enclosed within moister miombo woodland. The slender-tailed cisticola (Cisticola melanurus) is confined to grassy places in well-developed miombo. This bird is found mostly in northeastern Angola, and its presence in southwestern DRC is noteworthy given its restricted range and its rare localized populations. Several globally threatened water-associated birds have also been recorded in the ecoregion. These include: wattled crane (Grus carunculatus, VU), slaty egret (Egretta vinaceigula, VU), corncrake (Crex crex, VU).

Reptile and amphibian endemism is high. Nineteen reptiles and thirteen amphibian taxa are considered strictly endemic to the ecoregion. An example amphibian endemic species is the Shaba Province Toad (Amietophrynus fuliginatus), which occurs in Upemba National Park in the Democratic Republic of Congo and in portions of the Kafue National Park in Zambia, as well as in other locations up to 1880 meters in elevation. Several other of these endemic species are confined to the area within and around the Upemba National Park in the Shaba district of DRC, which is a local center of biological importance within the ecoregion as a whole. However, these high levels of local endemism may be a result of insufficient sampling rather than a true representation of an elevated biodiversity importance of this area. Distribution ranges for some of these apparently narrowly endemic animals may therefore be much greater than presently assumed. There are numerous other amphibians in the ecoregion, including the African clawed toad (Xenopus laevis), African ornate frog (Hildebrandtia ornata), African Peters frog (Hoplobatrachus occipitalis), African split-skin toad (Schismaderma carens), Angola forest treefrog (Leptopelis cynnamomeus), and Banded banana frog (Afrixalus fulvovittatus). Other amphibians found in the ecoregion include Darling's frog (Hylarana darlingi), which is often seen in the ecoregion whose breeding habitat is met for this amphibian that requires lentic or lotic waters for egg deposition. The Nile crocodile (Crocodylus niloticus) and the African sharp-nosed crocodile (C. cataphractus) are also found in the Zambezian Miombo woodlands ecoregion.

Current Status

Other than areas of the ecoregion located in densely populated Burundi and Malawi, relatively intact miombo woodland still covers a significant part of Central Miombo ecoregion. About 40 percent of Zambia and Tanzania were still covered by miombo, and large areas also remain in southern DRC. These miombo areas contain near-wilderness regions with few humans and many tsetse flies. However, even in those countries where large areas of miombo remain, much has been modified by humans. More than 95 percent of existing woodland cover in Malawi has been heavily modified. The vegetation of Burundi is also seriously degraded. Although there are large areas of miombo remaining in Tanzania, some of the woodlands of the Tabora region in Tanzania comprise secondary forest. This modification has a long history, and some areas of current wilderness have been populated in the past. The portion of the ecoregion in the DRC is under relatively less pressure due to low human population densities. However, intense civil war since 1998 has exposed roughly 16 million people (about one-third of the population) to hunger, disease, and homelessness. This fighting has undoubtedly had numerous consequences for the conservation status of the ecoregion.

In general, the ecoregion has a good protected areas network, with more than a dozen national parks, 13 game and wildlife reserves as well as numerous communally managed conservation areas in the southern African portion of the ecoregion. More than thirty percent of the total area of Zambia and around 25 percent of Tanzania is declared protected; much of this area is found in the miombo woodland habitats, partly within this ecoregion. Of the fourteen national parks found in the ecoregion, two stand out as being of particular conservation concern or ecological importance. Kafue, the oldest and largest national park in Zambia, consists of a mosaic of extensive grasslands, miombo, mopane, and riverine woodland. It supports most of the prominent mammals of the ecoregion, such as buffalo, elephant, sable, roan, Lichtenstein’s hartebeest, leopard, lion, spotted hyena and African wild dog, as well as several of the antelope found only in areas of permanent water, such as red lechwe and puku. Bird life is extremely prolific with about 450 species recorded, including many of the globally threatened birds previously mentioned. The other protected area worthy of special mention is Upemba National Park in southern DRC, which has been identified as a Center of Plant Diversity by WWF and IUCN (1994) with Cyphia brachyandra var. witteana, Lobelia lasiosalycina and L. molleri included as noteworthy species. The area also hosts the threatened black-faced waxbill (Estrilda nogriloris). Although it is not listed as an Endemic Bird Area, it is considered to be extremely important. Furthermore, of the 13 endemic anurans of the ecoregion, at least four are found solely in this park. Other national parks in this ecoregion include Ruvumbu in Burundi, Kundelungu in DRC, Kasungu and Nyika in Malawi, Katavi in Tanzania, and Kasanka, Lavushi Manda, Lusenga Plain, Mweru-Wantipa and Nsumbu in Zambia.

Types and Severity of Threats

Although much of the ecoregion is sparsely populated, there are only a few areas that have not been affected by anthropogenic activities in some way. High population densities in Burundi and Malawi have already resulted in severe loss of savanna woodland, increased habitat fragmentation, and diminished natural resources. In much of the remaining area, deforestation is one of the most widespread threats. Woodlands are being cleared for fuelwood, charcoal, and building materials as well as for agricultural land. More than 80 percent of people living in miombo depend on fuelwood and charcoal for cooking, heat, and light. Cutting woody vegetation for the production of charcoal, especially close to major roads and large urban centers has an ongoing marked impact on the miombo vegetation. In Zambia, it is estimated that between 1937 and 1983, 51 percent of the Copperbelt region had been deforested for both industrial and household wood fuel. The levels of charcoal production and deforestation are increasing constantly. In many areas, including Malawi, large numbers of saplings are removed from the woodlands to be used as poles for building traditional houses.

In Zambia, "citimene," a traditional form of ash-fertilizing agriculture is practiced. Trees more than 200 mm in diameter are pollarded and the branches dragged into an area about 100 m across. Once dry, this fuel is burned and crops are planted on the ash bed. According to Chidumayo (1996) this form of agriculture is unsustainable, as woody biomass is used at a greater rate than it can regrow. In addition, these ash gardens are abandoned after a few years, which means that in combination with population growth, this form of agriculture is resulting in escalated forest clearance.

The high incidence of fires in the area poses further threats to the ecoregion. Although fire is an integral part of miombo ecology, human setting of fires is believed to have increased the frequency of fire far above the natural level. Most of the deliberate burning and the uncontrolled fires occur at the end of the dry season, just before the onset of the summer rains. The fires burn with greater intensity as quantities of dry fuel accumulate. These hotter fires are destructive even to fire tolerant trees and can also have negative impacts because this season coincides with miombo trees breaking their dormancy. Repeated late-season fires in many areas have decreased forest regeneration, seed germination, and seedling survival growth can be severely disturbed. In addition, fire removes species that are less fire-tolerant from the miombo, thereby reducing species diversity.

Although large-scale cultivation is relatively uncommon, subsistence agriculture is practised by about 75 percent of the indigenous population. Growing staple and cash crops such as maize, cassava, sorghum, millet, and tobacco, pose significant threats to areas of the ecoregion, such as in Zambia, Tanzania and Malawi. Growing tobacco for export has lead to large losses of woodland for both land and fuelwood. These losses increase each year as new land is cleared to avoid the risk of root-knot nematodes. The curing of tobacco, is presently carried out using charcoal, compounding environmental problems. Livestock pressures are also high, with overgrazing being a common feature in the more heavily populated areas. In Tanzania, increased clearing of land for agriculture and grazing is a growing problem, as is illegal encroachment of people and livestock on protected areas in Zambia.

Of the industrial activities occurring in the ecoregion, mining in Zambia and DRC poses one of the greater threats. Land degradation and water pollution are just two of the problems caused by mineral prospecting, extraction, and processing. After the mining is complete, large tracts of land covered with mine waste dumps, where slag lies barren. Furthermore, reports from the Copperbelt have shown that the copper content in rivers found in affected areas has been up to 80 times higher than the safe level. This toxicity has serious consequences for conservation of the area, as elevated levels of copper are lethal to animals and people.

Poaching and illegal hunting for bushmeat have a significant impact on the wildlife throughout the ecoregion. Elephant and rhino poaching has been extremely severe throughout the ecoregion. Of the protected areas listed, those with sizable remaining populations of elephants are only the Kafue National Park, Zambia (approximately 4,500) and the Nkhota-Kota Wildlife Reserve in Malawi (approximately 1,000) (Barnes et al.1998). Most of areas outside parks and reserves have relatively little wildlife left, except perhaps in the remote interior parts of Tanzania. The live animal trade in Tanzania is one of the biggest in Africa, especially in birds and tortoises, which can potentially severely deplete local populations. Some of the species involved are captured in the miombo habitats.

The ongoing civil war poses one of most serious conservation threats in the DRC. It has led to general collapse of government structures, widespread insecurity, mass displacement of people, and a depressed economy. Conservation is, as a result, a low priority of government, non-governmental organizations, and the general public. In an atmosphere of ineffective environmental management, poaching of wildlife for subsistence and to finance the war will continue unchecked until political and social stability can be restored to the country.

Justification of Ecoregion Delineation

The Central Zambezian Miombo Woodlands ecoregion falls within the Zambezian Regional Center of Endemism outlined by White (1993). This large ecoregion running diagonally from Lake Victoria to the Zambezi River represents part of White’s (1983) wetter Zambezian miombo woodland and Udvardy’s (1975) miombo woodland/ savanna. Despite being floristically poorer, an area of drier Zambezian miombo woodland north of the wetter miombo unit is included because of similar faunal compositions. Patches of mosaic of Zambezian dry evergreen forest and wetter miombo woodland and small areas of grasslands on Kalahari Sands are also incorporated in this larger unit. Lake Malawi forms the eastern boundary of the Central Zamezian Miombo Woodlands ecoregion. Areas of drier and wetter miombo woodland that fall to the east of Lake Malawi form the Eastern Zambezian Miombo Woodlands ecoregion.

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.

Neighbouring ecoregions

There are several tangent ecoregions:

To the east is the Eastern Miombo woodlands (AT0706), covering a large swath of south Tanzania from Lake Malawi (Nyasa) in the east to close to (but not reaching) Tanzania's Indian Ocean coast. Confined to the lower elevations of the Central African Plateau, this ecoregion is characterized by the low-nutrient vegetation which grows in the dry climate and poor soil. However, the combination of smaller ecotonal habitats allows the area to support a variety of mammals, including possibly the largest populations of African elephant and Painted hunting dog on the continent. Although the presence of the tsetse fly and the lengthy civil war in Mozambique has left the area sparsely populated, human populations and natural resource use are increasing in the area. In addition, the Mozambican conflict has left a series of national parks and game reserves in urgent need of rehabilitation.
To the north is the Victoria Basin forest-savanna mosaic (AT0721), situated in the northeast of Tanzania on the southern shores of Lake Victoria. The ecoregion is most noted for its high species diversity and endemism resulting from the mixture of habitat types and species from both western and eastern Africa. Add the scattered wetland habitat, and you get an abundance of animals representing different habitat types. These include more than 310 species of trees and shrubs, 280 species of birds, 220 species of butterflies, and one hundred species of moths. The tropical moist climate here has two rainy seasons--one in April and May and another in October and November. These help replenish the waters for the many wetland areas of the ecoregion.

Additional information on this ecoregion

To view the vertebrate species that are found in this ecoregion, including threat levels, see the WWF Wildfinder description of this ecoregion.

Citation

World Wildlife Fund, C. Michael Hogan (May 6, 2014) Central Zambezian Miombo woodlands. ed. Mark McGinley, Encyclopedia of Earth, NCSE, Washington DC Retrieved from http://editors.eol.org/eoearth/wiki/Central_Zambezian_Miombo_woodlands

Central Zambezian Miombo woodlands

Contents

Terrestrial Ecoregions Collection

Location and General Description

Biodiversity Features

Current Status

Types and Severity of Threats

Justification of Ecoregion Delineation

Neighbouring ecoregions

Additional information on this ecoregion

Further Reading

Citation

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