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Site description (2001 baseline):
Site location and context
The Zambezi river, one of Africa’s four great rivers, is 2,700 km long; draining a huge basin of 1.4 million km². For almost its entire length along Zimbabwe’s northern border it lies in a rift valley, which is called the Gwembe trough at Lake Kariba, and the Zambezi valley downstream of the Kariba gorge. From the northern exit of the Kariba gorge at Nyamuomba Island (16°22’S 28°51’E) to the western entrance of the Mupata gorge (15°38’S 30°02’E), the river flows eastwards through 178 km of flat wildlife country, and forms the international border with Zambia to the north. The rift valley consists of a flat plain (at an altitude of 350–600 m) flanked by rugged escarpments that run parallel to the river, nearby in Zambia (highest point 1,286 m) and far to the south in Zimbabwe (highest point 1,288 m). The valley floor is much more extensive on the Zimbabwean side, where it covers an area of c.6,825 km². In some places the Zambezi river is 2 km wide or more, and it flows around many sandy islands. The river water is considered to be very clean, if rather nutrient-poor.
There are three main vegetation-types in the valley. Most of the valley floor supports mopane woodland, which in places can reach impressive proportions. The river’s alluvial deposits support riparian woodland, dominated by
Faidherbia but including many other trees such as
Kigelia,
Lonchocarpus and
Trichilia. The third main vegetation-type is colloquially known as ‘jesse’ bush, but is correctly labelled as mixed-species layered dry forest. This is deciduous and has a thicket-like understorey. It is rich in both tree and shrub species, for example
Pterocarpus,
Xeroderris,
Commiphora,
Berchemia,
Combretum and
Acacia among many others. The whole of the middle Zambezi valley on the Zimbabwe side is under Parks and Wild Life Estate, except for about 50 km² of commercial land around Chirundu.
See Box and Table 3 for key species. Among globally threatened species,
Gyps coprotheres is only very rarely recorded, as too are
Ardeola idae,
Phoenicopterus ruber and
P. minor. A few of the Zambezian-biome birds live in the valley (although miombo woodland as such does not occur on the valley floor), for example
Coracias spatulata,
Nectarinia talatala,
Vidua obtusa and
Lamprotornis mevesii. The valley is home to more than 400 species of birds, and among terrestrial species it is the only locality so far known in Zimbabwe for
Nectarinia shelleyi, and is particularly important for
Agapornis lilianae (many thousands; more than 1% of the global population),
Bucorvus cafer (occurring at a very high density),
Erythrocercus livingstonei and
Guttera pucherani.
Among waterbirds, the species richness in the valley is very high, at c.90 species, although relative abundances are lower. The banks of the Zambezi provide nesting habitat for c.10,500
Merops nubicoides, with unknown extra numbers in tributaries along the valley floor. The sandbanks and sandy islands form equally essential habitat for
Rynchops flavirostris, and in 1986 a survey estimated 136 birds on the stretch of river in the valley. In the same year, about 320
Glareola nuchalis were counted in the Kariba and Mupata gorges (strictly outside the presently-defined area). Also of special interest are
Ardeola rufiventris,
Ciconia episcopus,
Vanellus albiceps,
Plegadis falcinellus,
Nettapus auritus and
Burhinus vermiculatus. Numbers of the first three species exceed the 1% threshold of their global populations.
Also, at least 52 species of raptor (including owls) have so far been recorded in the valley, including large numbers of
Haliaeetus vocifer (c.1 pair per 3 km frontage) and an unknown number of
Scotopelia peli. Being such a huge wildlife area, there is a good representation of vultures (six species) and eagles (12 species).
Non-bird biodiversity: All individuals of Diceros bicornis (CR) in the valley were either killed by poachers or translocated between 1984 and 1994. A small amount of poaching continues, on elephants and antelopes; it is thought that there is considerable poaching of fish from the Zambian side. The valley supports a full range of predators, including wild dog Lycaon pictus (EN). The river is famous for its huge numbers of hippos Hippopotamus amphibius (several thousands) and crocodiles Crocodylus niloticus.
Pressure/threats to key biodiversity
The whole of the valley floor within this site lies in the Parks and Wild Life Estate. In the centre is the Mana Pools National Park, flanked on its west by the Hurungwe Safari Area, and on its east by the Sapi and Chewore Safari Areas. Controlled hunting on quota is permitted in the safari areas. The valley, particularly along the Zambezi river, is fully patrolled, and has been protected for a very long time, not only by legislation but also by inaccessibility and by tsetse fly
Glossina. However, the fly was eradicated a few years ago. The Zambezi valley on both sides of the river is a World Heritage Site.
There are two main threats to the integrity of the area. The fundamental one is that the Zambezi river no longer floods in its original regime due to the Kariba Dam upstream, and to a lesser extent the Kafue Dam upstream on that tributary. Indeed, apart from in 2000, the last time that Kariba’s flood-gates were opened was in 1981. Thus the sandy islands in the river are no longer scoured by floods and are becoming consolidated and grown over by invasive
Acacia.
Secondly, the protection of the valley has resulted in population explosions of elephants
Loxodonta africana and impalas
Aepycerus melampus, in particular in the national park. Undergrowth and grass are removed, regeneration is prevented and trees are damaged, resulting in open areas and greatly increased water run-off, leading to flash floods and collapse of banks. Wild-fires also occur annually in the dry season.
Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Middle Zambezi Valley (Zimbabwe). Downloaded from
https://datazone.birdlife.org/site/factsheet/middle-zambezi-valley-iba-zimbabwe on 23/12/2024.
