SPECIAL SECTION: LAND USE OPTIONS IN DRY TROPICAL WOODLAND ECOSYSTEMS IN ZIMBABWE A simulation model of miombo woodland dynamics under different management regimes

Miombo woodlands are crucial to the livelihoods of rural people throughout southern, eastern and central Africa. This paper describes a dynamic simulation model of key ecological processes in miombo and examines the ecological and economic impacts of various forms of management. The model shows that removing harvestable trees and reducing the level of grazing by livestock causes an increase in grass fuel loads and a corresponding increase in the frequency of fires. More frequent and intense fires in turn suppress woody regrowth, thereby adversely affecting harvestable tree stocks. Despite the marked ecological response to manipulating the level of grazing, the impacts on economic performance were minimal. The NPVs for Forestry Commission in particular remained relatively constant under different management regimes. Given these low potential returns, the advantage of applying some of the known silvicultural management treatments to miombo woodlands seems questionable. Varying the proportion of harvestable timber trees cut and changing the length of the cutting cycle might suggest that profits to the Forestry Commission or timber concessionaires could be maximised by harvesting as much timber as possible in a single cutting period. Under such a scenario, however, the woodland would be rapidly converted to bushland. There is a need to explore further the trade-offs between direct use values, as derived from harvesting and selling timber, and ecological service functions, such as carbon sequestration and modifications of the hydrological cycle. © 2000 Elsevier Science B.V. All rights reserved. www.elsevier.com/locate/ecolecon