Zambezian flooded grasslands
The Zambezian Flooded Grasslands are a unique ecoregion located in south-central and central-east Africa, characterized by low-lying areas that are seasonally or year-round inundated with water. This biome forms a scattered archipelago of grasslands, primarily situated in the watershed of the Zambezi River and extending into portions of neighboring river basins. It spans a diagonal band from Tanzania through Zambia to Namibia and Botswana, offering a diverse habitat that supports a rich variety of plant and animal species.
The environment features a high level of vegetation productivity, with extensive grasses, sedges, and reeds thriving in the wet conditions. This fertility provides a stark contrast to the surrounding drier woodlands, supporting large herds of wildlife, including elephants, buffalo, and various antelope species, along with numerous bird species, some of which are endemic to the region. Climate-wise, the area experiences a tropical seasonal pattern, with hot, wet summers and warm, dry winters.
However, the Zambezian Flooded Grasslands face significant threats from human activities, including agriculture, poaching, and habitat loss, exacerbated by climate changes and water management practices. Despite the existence of protected areas, the delicate ecosystems within this ecoregion continue to be at risk, highlighting the need for ongoing conservation efforts.
On this Page
Subject Terms
Zambezian flooded grasslands
Category: Grassland, Tundra and Human Biomes.
Geographic Location: Africa.
Summary: An ecoregion of extraordinary productivity and species abundance, this biome is at risk from accelerating deforestation and related threats.
The Zambezian Flooded Grasslands ecoregion is a land-based archipelago of grasslands spread across south-central and central-east Africa. It consists of low-lying areas inundated seasonally or year-round, either in the immediate watershed of the vast Zambezi River or in smaller portions of other neighboring river basins. The ecoregion is located in pockets throughout a band stretching diagonally from Tanzania, in the miombo and mopane woodlands south of Lake Victoria in its northeast range, through Zambia and the Central African Plateau, to Namibia and Botswana at the verge of the Kalahari Desert at its southwest extreme.
This scattered biome is characterized by unusual vegetation productivity among grasses, sedges, reeds, and other swamp types, as well as faunal abundance. Both stem from the availability of water and food for most of the year. This abundance of both animal and plant species is in stark contrast with the drier, nutrient-poor expanses of woodlands surrounding much of the ecoregion’s land islands, which can only support animals in relatively low densities.
Climate
The region is characterized by a seasonal tropical climate with two distinct seasons: hot and dry from April to October, and a hot and wet summer between November and March. Temperatures vary due to the broad spread across the continent, with high temperatures ranging at 64–81 degrees F (18–27 degrees C) and low temperatures ranging at 48–64 degrees F (9–18 degrees C). Altitude of a given locality here is a strong factor in the temperature regime.
Precipitation amounts vary similarly, from a lower range of 18–24 inches (450–600 millimeters) annually, to a maximum of up to 55 inches (1,400 millimeters). There are pulses of stream inflow from associated highlands, and when these hit the generally clay-bed soils of these flatlands, a waterlogged situation easily develops and often persists throughout the year. This depends on evaporation and precipitation rates, as well as particular drainage outlets and wind conditions.
Flora and Fauna
Floristically, the Zambezian Flooded Grasslands biome is situated at the heart of some of the largest centers of endemism (species found nowhere else) within Africa. Given the spread of these fertile and fecund marshes and grasslands across a broad belt of the continent, it is in many ways ideal as a corridor system for an incredible variety and richness of species. Papyrus is a familiar and dominant reed form here, and is joined by grasses of genera Phragmites, Echinochloa, Oryza, Acrocera, and others. Mudflats, thickets, and floating vegetation join with these grasses to provide a range of habitat. These are supplemented by such accents as never-flooded dry islands built up atop generational termite mounds, and some stands of trees upon the better drained fringes.
Wildlife species here range from crocodiles to herd antelopes, as well as charismatic mega-fauna and carnivores, to an incredible variety of avian species. The ungulate fauna feature very large herds of Burchell’s zebra, eland, lechwe, puku, wildebeest, African buffalo, tsessebe, waterbuck, reedbuck, and kudu. Elephants and hippopotamuses are in great supply—as are many large carnivores such as lion, leopard, cheetah, and, not least, the crocodile. Endemic and globally rare avian species include several species of weaver, Chaplini’s barbet, egrets, blue crane, guineafowl, and black korhaan.
Human Interaction
The Zambezian Flooded Grasslands biome has a built-in attraction for farmers, herders, hunters and poachers—it also is a vital water supply for people struggling to get though dry seasons. Given the attractiveness to tourists, growing indigenous populations, and climate patterns tending toward hotter and drier, this ecoregion is increasingly being threatened by biodiversity- and habitat-loss, despite the numerous protected areas and conservation measures already in place to protect these delicate ecosystems.
The biome is also increasingly at risk from deforestation of its surrounding woodlands, diminution of water flow from human diversion, and pollution of the water quality by ill-controlled land-use practices upstream. The presence of hydroelectric dams in the region has also altered the flooding patterns in some areas, impacting the breeding habitats of several species of cranes.
Protected areas include some areas set aside in a sprawling range of ecozones, including Barotse Floodplain and Kafue Flats in Zambia, Lake Chilwa in Malawi, Okavango Delta in Botswana, and some Tanzanian floodplains.
Bibliography
Chabwela, H. N., and W. Mumba. “Integrating Water Conservation and Population Strategies on the Kafue Flats.” In A. de Sherbinin and V. Dompka, eds., Water and Population Dynamics: Case Studies and Policy Implications. Zambia. Washington, DC: American Association for the Advancement of Science, 1998.
Martin, Emma, and Neil Burgess. "Zambezian Flooded Grasslands." One Earth, 2022, www.oneearth.org/ecoregions/zambezian-flooded-grasslands/. Accessed 8 Aug. 2022.