Africa

F7

a

Insects as Carriers of Disease

In colonial times, Europeans referred to Africa as the “white man’s grave,” reflecting the fear of life-threatening tropical diseases for which non-Africans lacked natural resistance. The leading cause of death—among colonists and Africans alike—was malaria. The malaria parasite is transmitted to humans by the bite of the female Anopheles mosquito. The World Health Organization (WHO) launched a worldwide campaign to eradicate malaria during the 1960s by spraying homes with insecticides, draining breeding sites, and dispensing antimalarial drugs. The campaign failed: Parasites developed genetic resistance to drugs, mosquitoes became resistant to insecticides, and impoverished governments lacked the resources to develop a comprehensive strategy against the disease. Today, malaria remains Africa’s leading cause of death.

Various species of tsetse fly are another scourge of Africa. The tsetse transmits the Trypanosoma parasite, which causes the often-fatal disease trypanosomiasis, also known as sleeping sickness in humans and nagana in livestock. The prevalence of tsetse is believed to be a major factor in settlement patterns in Africa, including the low population densities of large areas of the savanna. Because cattle are especially vulnerable to trypanosomiasis, the full economic potential of vast areas of fertile grassland has not been realized. Certain colonial policies heightened the tsetse scourge: The creation of game reserves increased populations of wild animals that serve as natural reservoirs of the Trypanosoma parasite; and resettlement schemes increased human contact with tsetse and brought about major epidemics of sleeping sickness. An epidemic in the early 20th century wiped out some two-thirds of the population of what is now Uganda. Colonial control programs eventually succeeded in limiting, but not eliminating, the tsetse and the diseases it transmits.

The black fly Simulium damnosum has had a major impact on settlement in Burkina Faso and several other countries in West Africa. This insect, which breeds in fast-flowing streams, transmits a parasitic worm that is responsible for onchocerciasis, also known as river blindness, which causes blindness and severe skin problems. As rates of infection and blindness increased in villages close to fly-breeding sites, local economies were weakened and eventually the village sites were abandoned. The WHO initiated a control program during the 1970s, using insecticides to kill larvae of the fly, and chemotherapy to treat infected people. This program has succeeded in interrupting the transmission of the disease in most of the affected areas.

F7

b

Termites

The forests and savannas of Africa are home to some 400 species of termites. Termite mounds vary in size, depending on the termite species and on soil conditions: Some may be up to 9 m (30 ft) tall, with nests extending up to 15 m (50 ft) underground. Vast numbers of termites inhabit these nests; densities as high as 9 million termites per hectare (4 million per acre) have been recorded.

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Termites are both friend and foe to humans. Termite colonies enhance soil fertility by transporting and concentrating fertile subsoil clays near the surface and by increasing soil aeration. African farmers seek out termite mounds and plant crops around them—yields are usually higher from crops in these sites. Conversely, termites consume vast quantities of organic matter, and are blamed for increased soil erosion that may occur around termite mounds.

F7

c

Locusts

Three main types of locusts are found in the dry savanna and semidesert areas of Africa: the desert locust and the African migratory locust, found north of the equator, and the red locust, which occurs in south central Africa. These locusts occasionally congregate in large swarms to migrate in search of food. Following the direction of prevailing winds, they devour everything green in their path, including entire crop harvests. Spraying programs to control populations and routine monitoring to detect the first signs of swarming have reduced the serious threat that locusts once posed to agriculture. However, locusts can still sometimes cause significant damage at a local or regional scale.

G

Environmental Issues

Africa is widely seen as a “devastated continent,” where inappropriate human use of land has caused deforestation, desertification, and soil erosion on a massive scale. This view of Africa has greatly influenced academic research agendas and international aid programs, as well as public perceptions of the continent. But some scientists are increasingly questioning this view of environmental degradation. They emphasize the need to ascertain whether degradation is actually occurring, how human actions affect the process, and what conservation measures are needed. In some cases, Western viewpoints and ideas have led to misguided attempts at conservation that had no effect or even an adverse effect on the environment. At the same time, some African conservation methods were discovered to be much more effective. Going forward, many experts argue that conservation strategies must be sensitive to regional and temporal variations and should seek to preserve and build upon local indigenous knowledge.

G

1

Soil Erosion and Desertification

Until recently, there was widespread consensus among scientists and policymakers that African soils were threatened by ill-advised traditional farming methods that increased soil erosion and desertification (the process in which soil dries out until almost no vegetation grows on it). Policy documents used limited, often flawed case studies to produce continent-wide generalizations in which worst-case scenarios were too often presented as typical. In reality, the nature and extent of soil erosion and desertification varies greatly throughout Africa and much of it is unrelated to human activity. For example, savanna regions are subject to wind erosion in the dry season, which is the primary cause of soil erosion in arid and semiarid environments.

The Sahel, a semiarid savanna region located to the south of the Sahara, experienced a severe drought from the late 1960s to the early 1970s. In reaction, Western scholars propagated a popular view that the Sahara was expanding year by year, relentlessly enveloping once-productive land. Further research has shown that, while soil degradation was confirmed in some areas, in many parts of the Sahel there was little evidence of degradation, and none of steady desert expansion. During the colonial era, the perception of imminent crisis led to policy initiatives designed to preserve the soil. Colonial administrators attempted to control the perceived problem of erosion by enforcing restrictions on herding and agriculture, restricting the use of fire to clear land for agriculture, and installing grass and stone barriers along slope contours. These measures were generally resented by the local African population, and they had little impact on erosion rates. Similarly, attempts to control desertification through policies such as planting shelter belts of trees and restricting nomadic herding have had limited effect.

Scientific research has demonstrated that indigenous African farming and herding practices are much less harmful to the soil than was formerly believed. Methods such as retaining farmland trees, growing crops on ridges, and interplanting different crops densely in a single field significantly reduce soil erosion. On the other hand, modern cultivation methods—involving the use of mechanical equipment, row cropping, and weed control with herbicides—greatly increase the risk of soil loss. Similarly, problems of soil erosion and degradation are greater in areas with fenced cattle ranches than in places where traditional livestock practices are followed, with animals grazing less intensively over a very large area.