Ecosystem heterogeneity and lack of data on areas and deforestation rates have constrained the modelling of deforestation in tropical open woodlands. Smaller and more continuous changes in ecosystem quality attributes (e.g. canopy cover, tree density and biomass density) are best described as degradation, not deforestation. Suggestions are made for constructing degradation models by relaxing some assumptions of deforestation models to cope with the multiple uses of multiple vegetation layers by multiple users. Employing biomass as a dependent variable would account for biomass reductions caused by changes in woodland area, tree density and the biomass of retained trees and shrubs, and overcome the problem of how to aggregate changes in woodland area and tree density. Disaggregating models by woodland type is also recommended.