Vectors, pests and environmental change

Tsetse fly control in East Africa

Development in the East African colonies was adversely affected by disease vectors such as tsetse flies (Qlossma species)103 that, from the beginning of the colonial period, had posed a great threat to public health and to pastoral and agricultural production (Chapter 8). Tsetse flies and the trypanosome protozoan that cause disease in people and livestock present one of the most stubborn ecological and epidemiological problems ever encountered by imperial science.104 The tsetse flies by the late nineteenth century had infested an estimated ten million km2 of Africa, along a fly belt that strad- dies the rain forest into the dry savanna, south of the Sahara and north of the Kalahari deserts.105 An estimated seven million km2 of rangelands and agricultural lands were affected, covering 75 percent of Uganda, two-thirds of Tanganyika and 20 percent of Kenya.106 The Qlossina species10, exploited varieties of ideal habitats,108 including bushlands and the vegetation of river valleys.109 The tsetse flies take their blood meals from vertebrate hosts in a process through which the life cycle of the trypanosome protozoan circulates between infected insects, people, cattle and wild game. To date, there are no known permanent medical solutions to stop infection by the trypanosome parasites that cause trypanosomiasis (sleeping sickness).110

The control of, and research into, tsetse flies and trypanosomiasis attempted varieties of methods, including the destruction of the habitats through bush clearing, destruction of the wild game and the application of environmentally persistent pesticides. Another attempted control method was the removal of people and livestock—however, this process allowed the tsetse to expand their frontiers.111 In the process, millions of hectares of natural vegetation were cleared, although the outcomes of such interventions were not discussed in the context of the African environmental crisis. The problem would also apply to African locust plagues as the most destructive agents of the environment and economies of the East African colonies.

Locust invasion and control

The East African region had been periodically visited by plagues of desert locusts (Schistocerca gregaria Forsk) and red locusts (Nomadaries septermfas- data Serville) that ruined agricultural and pastoral economies in East and the Horn of Africa (Chapter 9). The desert locust is among the most widespread pests, with breeding grounds extending from the deserts on the Indo- Pakistan borders, the Arabian Peninsula, the Red Sea coast, to Somaliland and some regions of East Africa. The red locust breeds in the floodplains of Uganda, as well as southern Tanzania in the region of Lake Rukwa from where they pose a great danger to the economies in East Africa.112

Locusts are voracious feeders, consuming huge amounts of vegetation and crops on their flight paths or in their development stages, causing economic losses in millions of British pounds. Huge financial resources had been committed over a period of half a century to control the plagues. Efforts to control the desert locust and the red locust115 had motivated international collaboration. Control methods involved mobilizing African labor to attack the pest during its various phases of development. Both ground and aerial methods were used to spray the swarms. Aerial spraying was popular for controlling mobile swarms in flight between the outbreak areas and the target regions in East Africa. Although effective, the methods did not eliminate different generations of swarms; thus, locust control was always a state of emergency, allowing little time to conduct controlled experiments. The destruction of agricultural economies caused by locusts occurred at a time when researchers and colonial officials were blaming local land-use methods for environmental crisis.

These and other related discussions will be expounded in the coming case study chapters (under the three themes: empire, science, society and development; experimental and social science research; and vectors, pests and environmental change). In the final chapter of the book (Chapter 10), we synthesize the key findings of the work and in an epilog, map out the progress of scientific research for development during the later periods of post-independence.

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