Optimisation of the traditional land-use system in the Angolan highlands using linear programming

This study used linear programming (LP) to analyse land-use alternatives in the traditional Umbundu farming system in the Angolan central highlands. Farmers of the region have traditionally produced maize and pulses for subsistence and vegetables and timber as cash crops. Different pasture and forest fallow rotations are used along catena production sites. The system is labour-intensive and uses animal traction. LP problems were formulated and solved for a baseline land-use alternative, improved diet alternative and maximal timber production alternative. All three problem formulations included constraints that guaranteed sufficient food and firewood production and sufficient pasture area for animals while being feasible in terms of human labour and animal traction consumption. Of the alternative production systems, cash crops with forest fallow had the highest land expectation value (LEV), while cereals under short grazing fallow showed even negative LEVs. Changing the diet by diversifying carbohydrate and protein sources increased LEV and reduced the need for women labour during the peak season. When timber production was maximised the optimal share of land devoted to pure forestry was 57%, and less labour was required.