Notes

1. Statistical information on agricultural performance, as on most other aspects of social and economic development, is difficult to obtain and tends to be of poor quality. This study craws on what is generally considered to tee the best available statistical information (see the Statistical Appendix for data and sources).

2. The data on which estimates of food avallability and consumption are based (such as crop acreage, yields, livestock production, processing and storage losses) are of poor quality in most African countries. Increasingly, it is also recognized that noncultivated plants and "bushmeat'' contribute far more to many Africans' diets, particularly in poor crop years, than has been captured in official statistics Nevertheless, few observers are as skeptical of the general picture of serious food deficits as Svedberg (1991).

3. Demographic modeling of the potential impact of AIDS m extremely difficult Some simulations suggest that AIDS may reduce the population growth rate of SSA as a whole by as much as 05 to 1.0 percentage points in the early decades of the 21st century—through drastically higher mortality rates. But higher mortality rates may delay fertility declines.

4. UNDP/World Bank (1992), Tables 14-8 rough 14-1, provides country-specific data on energy consumption, including consumption of fuelwood.

5. The InterAfrican Committee on Medicinal Plants and African Tropical Medicine and the Scientific, Technical and Research Commission of the OAU fave published a pharmacopeia of African medicinal plants of proven efficacy, African Pharmacopeia (1985), and several African countries }rave established research institutes focusing on traditional medicine and the sources and effects of the active ingredients in medicines administered by traditional healers (DeJong 1991).

6. WRI/IIED estimates are even higher, suggesting that more than 80 percent of SubSaharan Africa's productive drylands, some 660 million hectares, are affected by "desertification" (Table A-27).

7. The Sub-Saharan Africa Hydrological Assessment attempts to meet this need by assisting countries to develop a reliable hydrological data base (see Chapter 10, note 1).

8. In Cd'Ivoire, where deforestation has been the most rapid, mean annual rainfall declined significantly during the 1970s and 1980s (World Bank 1989a). Rainfall in Senegal decreased by 2.2 percent a year in the 1970s and 1980s, and there was a sharp decrease in rainfall in northern Nigeria and Cameroon (Lele 1989c; Lele and Stone 1989). Rainfall also declined dramatically throughout Ethiopia during that period (World Bank 1987a).

9. Cloud droplets form around aerosol particles, called cloud condensation nuclei (CCN). Biomass burning generates and releases into the atmosphere vast amounts of pyrogenic aerosol particles, which are very effective as CCN. The more CCN in the atmosphere, the more droplets form, resulting in smaller droplet size with a given amount of available water. Clouds composed of smaller droplets are lighter in color' reflect more sunlight bade into space, and are less likely to produce rain. Since clouds are a major regulatory and control mechanism for the Earth's heat balance, large scale modifications in cloud properties have a strong impact on global climate. The increasing abundance of CCN is, therefore, likely to have potentially critical impact on precipitation efficiency—compounding the changes in hydrological cycles in the tropics caused by land surface changes such as deforestation (Andreae and Goldammer 1992:87-88).

10 See, for example, Barnes 1990a and 1990b; Bishop and Allen 1989; Elliot 1986; Falloux and Mukendi 1988; Gorse and Steeds 1987; FAO/IBRD Cooperative Programme 1991; Lal and Okigbo 1990; Matlon 1990; de Montalembert and Clement 1983; Mortimore 1989a and 1989b; Nelson 1988; Stocking 1987.