A Primer on Savanna Ecology.
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Savanna is one of the world's major biomes (Figure 1). It occupies 54% of southern Africa, 60% of sub-Saharan Africa and 20% of the global land surface (Scholes and Walker, 1993). Furthermore, a large proportion of the world's human population and the majority of range-lands and livestock are found in savannas (Werner, Walker and Stott, 1991). Savannas contribute to both the informal and formal economies of many countries (Campbell, 1996). They supply grazing, fuel-wood, timber and other resources to the informal and subsistence economy. Savannas also contribute to the formal economy because they are the main location of the livestock and eco-tourism industries. Globally, savannas are important because of emissions of trace gases from fires, soils and animals (Justice, Scholes and Frost, 1994); sequestration of carbon in their soils and biomass; and their biological diversity. Savannas are, however, experiencing increasing pressures from demographic and economic changes that have increased dramatically over the past few decades. Severe damage to vegetation and soils is evident in. several regions (Werner, Walker and Stott, 1991). A further threat to the structure and functioning of savannas is the forecast of global warming and likely changes in precipitation pattems.