48. With or without tsetse control, development of the Zambezi Valley is likely to be rapid in the coming years, with planned and spontaneous settlement continuing in response to the high population pressures elsewhere in the country. With or without tsetse control, environmental degradation is likely to occur through deforestation, streambank cultivation, poor arable land husbandry and other forms of natural resource abuse commonly associated with peasant farming under population pressure. The fragility of the Zambezi Valley is not threatened by livestock numbers alone, but overstocking is one of the more important factors contributing to the degradation of land in the communal areas of Zimbabwe (World Bank, 1986).
49. Without tsetse control livestock will be introduced to a limited extent with drug protection against trypanosomiasis where required. Support for mechanical tillage schemes or promotion of draught donkeys could alleviate draught constraints to a limited extent. However, the standard of living of communities settling in the Valley is likely to be depressed significantly without cattle ownership.
50. Without tsetse control, there is a significant risk of future outbreak of human trypanosomiasis in this area, a risk likely to be aggravated by the introduction of cattle (MacKenzie and Boyt, 1974). The Zambezi Valley is a smouldering focus of endemic human sleeping sickness, which has not proved a problem in the past as human settlement has previously been minimal in the area.
51. With tsetse control, given that traditional farming systems are likely to be important in the future development of the Zambezi Valley, widespread introduction of livestock under proper management could make a substantial and positive contribution to rural development.
52. Where tsetse control is carried out in support of sustainable new settlement, the benefits extend not only to the new settlers in the Valley itself but also to the overpopulated Communal Lands where these people are coming from. Tsetse control can indirectly help to alleviate the population pressure in existing Communal Lands which is the fundamental cause of the environmental problems already being experienced in these areas. While the relief may be limited and short-lived, given the rapid rate of population growth, it cannot be ignored in a country where land shortage is one of the main constraints to rural development.
53. Complete abandonment of tsetse fly control in Zimbabwe would result, within a few years, in extensive reinvasion of communal and commercial farming areas in which livestock play an important role. More than 30% of the country is at risk of reinvasion (Map 1), and consequently, the Department of Veterinary Services will continue tsetse control activities in Zimbabwe for the foreseeable future. The important decision to be made concerns where to draw the holding line beyond which no further fly control will be attempted until such time, if ever, that eradication of the fly beyond the borders of neighbouring Mozambique and Zambia is in immediate prospect.
54. Land use issues in the areas of infestation are only one of the factors to be considered in deciding whether or not to eliminate the tsetse fly from a particular area. The Government is currently spending some Z$12 million (US $6 million) per year to defend a 600 kilometre tsetse front extending from Lake Kariba to Mozambique to the north of the Eastern Highlands. It is considered cost effective to clear the western part of the tsetse belt in Zimbabwe for the simple expediency of reducing the length of the front. This could save considerable future recurrent expenditure even if the areas cleared of the fly were to be designated for wildlife rather than livestock-related use.
55. It may also be justified to undertake tsetse control in an area where there are no direct economic benefits likely to result from change in land use, but where major reservoirs of fly infestation exist and threaten neighbouring farming areas.
56. The rate of progress and priorities for tsetse control will have to be planned taking into account all the financial, socio-economic and land use factors relevant to each part of the tsetse fly front, considerations which are likely to change from one year to the next as development of the Zambezi Valley continues. In this context, ongoing monitoring and evaluation of the socioeconomic aspects of land use in the tsetse-infested areas will be prerequisites to sound planning of future tsetse control activities in the Zambezi Valley.
57. Economic evaluation will centre on benefit-cost analysis, ensuring cost-effective deployment of resources against tsetse and trypanosomiasis, and assessing the impact of tsetse control on the economics of alternative land uses, including both agropastoralism and wildlife utilization. But the work must also extend to the identification of projects, institutional and infrastructural support, policy measures and other inputs required to promote sustainable land use following tsetse control, in particular relating to livestock development and draught assistance.
58. The building of stronger links between tsetse control policy and rural development planning has the implication that future eradication of the fly from presently infested areas is likely to be a slow and cautious process. The lessons of tsetse control in Zimbabwe should have considerable value for decision-makers in neighbouring countries and for donors who could provide the funds required to eradicate tsetse from the common fly belt a reality. Resources may be allocated inappropriately unless full, proper and continuing attention is given to the social, economic and land use issues involved.
