Wetland Drainage: Page 3 Endangered Species Handbook

Aquatic Ecosystems

Wetland Drainage: Page 3

Africa's two largest wetlands are Botswana's Okavango Delta and the Sudd marshes of southern Sudan. Both are threatened by massive water projects that may result in draining them for agriculture. Civil war in Sudan has so far prevented the construction of the Jonglei Canal, which would drain large sections of the wetland. The Sudd, covering 6,370 square miles when flooded by the Nile, is a maze of lakes, rivers and papyrus swamps among lush grassland and woodland savannahs (Simon 1995). It has the richest diversity of birds of any African wetland. The extraordinary shoebill, or whale-billed stork (Balaeniceps rex), the sole member of its avian family, is resident. This stork-like bird, whose scientific name means "whale-headed king," resembles a creature imagined by Dr. Seuss, with an outsized head and huge primitive beak ending in a long hook. The papyrus swamps that are the bird’s habitat are being drained throughout their range, which extends from Sudan south to Zambia. Fires set in the swamp, civil wars and large numbers of cattle tramping vegetation and destroying nests in the Sudd and elsewhere have disrupted protected areas such as the Akagera National Park in Rwanda (BI 2000). Tanzania's population of 2,000 birds is one of the few stable ones, newly protected as the country's first Ramsar site (BI 2000). Large numbers are captured for zoos, which exhibit this bird as a curiosity (Hoyo et al. 1992). The total population of this unique species was estimated at about 11,000 to 15,000 birds and declining in the late 1990s (BI 2000).

In the Sudd's floodplains and grassland are enormous herds of two antelope, the kiang, a subspecies of the topi (Damaliscus lunatus tiang) and the white-eared kob (Kobus kob leucotis). Almost a million of these antelope migrate to take advantage of grassland, forming the second largest aggregation of large mammals remaining in Africa after the wildebeest (Connochaetes taurinus) of East Africa. A film about these spectacular animals, “Mysterious Herds of the Sudan: Migration of the White-eared Kob” (see Video, Mammals), shows this landscape as well, a little-known corner of the Earth whose abundant wildlife may be decimated if the Jonglei Canal is constructed. Another threatened species that is found only in the Sudd and wetlands of adjacent Ethiopia is the Nile lechwe (Kobus megaceros), a wetland antelope with elongated hooves that spread the weight of its body to keep it from sinking and help it leap through shallow water in bounds. This black antelope has ridged horns that arch over its back and a goat-like appearance. The 2000 IUCN Red List lists it as near-threatened. The Nile lechwe's population totals about 30,000, but its range is restricted, and should its habitat be destroyed by water projects, it will be threatened with extinction (Nowak 1999).

In the middle of the vast Kalahari Desert is a brilliant, blue gem, the 11,000-square-mile Okavango Delta wetlands. This extraordinary wildlife oasis is the world's largest inland delta, a magnificent watery wilderness of shallow lakes, papyrus swamps, meandering rivers, wet grasslands and woodlands. World renowned for its large populations of zebra, antelope, African elephant (Loxodonta africana) and Cape buffalo (Syncerus caffer), the Okavango attract tourists in large numbers. Waterfowl are abundant, and the African fish eagle (Haliaeetus vocifer), which resembles the American bald eagle, is common. Fifteen species of marsh-dwelling antelope are native, many of which are unique to this region. One of these, the threatened red lechwe (Kobus leche), has a large portion of its population, some 30,000 animals, in the Okavango (Nowak 1999). A race of this antelope in the wetlands of Zambia, the Kafue lechwe (Kobus leche kafuensis), lost half its population of 100,000 in 1970 after the construction of two huge dams for hydroelectric power on the Kafue River, which radically altered the natural flooding and dried out much of its floodplain habitat (Nowak 1999). Another race of this species, Kobus leche smithemani, native to the Bangweulu Swamps of northern Zambia, fell from about 250,000 in the 1930s to around 30,000 today, as a result of hunting and disruption of water levels by human manipulation (Nowak 1999). Yet another race, Kobus leche robertsi, native to the Luongo and Luena River drainages of northwestern Zambia, is now extinct (Nowak 1999).

Cattle ranches have been carved out of portions of the Okavango, but until recently, this immense swamp remained nearly intact. Its precious water supply is now in decline. A major feeder of this swamp, the Kavango River, is now having much of its flow siphoned off by the Namibian government for agriculture and residential use. Botswana has objected strenuously to this project, but Namibia is determined to ease a severe water shortage caused by years of drought. The Boro River, which emerges from the delta, may be dredged and diverted for diamond mines (Postel 1997). These projects may end in draining the Okavango and destroying the enormously profitable tourist industry in Botswana (Hawker 1997). This wetland receives irregular rain which brings flocks of flamingos to nest and renews the water table, but should its feeder river be blocked, many of its unique wetland animals and sizeable herds of endangered African elephant may be lost.

Another threat to the Okavango Delta is the planned spraying of 7,180 square kilometers with the pesticide endosulphan, beginning in the winter of 2001 (Tyler 2001). The purpose is to destroy tsetse fly, the dreaded vector for sleeping sickness or trypanosomiasis (Tyler 2001). This pesticide is toxic to small fish and many other types of insects that are primary sources in the food chain for aquatic birds, such as herons and egrets. These birds breed during the winter months when the spraying is planned, and the threatened Slaty egret (Egretta vinaceigula), which breeds in the delta and has a world population of only 5,000 to 10,000 birds, is at serious risk (Tyler 2001). Ironically, the tsetse flies were being effectively controlled by the use of cloth baits soaked in insecticide and hung on poles, but they were not properly maintained by personnel, and stocks ran out (Tyler 2001). Conservation organizations are protesting to the Botswana government to stop the spraying and consider the environmental effects. Until recently, sleeping sickness was not an easily controlled disease, killing thousands of Africans. Native hoofed animals are immune to the disease. Recently, however, a new drug, DSMO, used in the United States to remove facial hair, has been found to be almost a miracle drug in awakening victims of this disease from their comatose states, without the side effects of available medications. One pharmaceutical company agreed in early 2001 to donate 3 years’ supply after pressure from various health organizations. This makes spraying toxic pesticides even more unnecessary.^*

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^*“Okavango. Jewel of the Kalahari,” a series of three one-hour films by Partridge Films and the BBC, shows the great beauty and wealth of wildlife in this wetland. (See Video, Regional, Africa; see also the Book Section for several books about this swamp.)

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