What can and can't we say about indirect land‐use change in Brazil using an integrated economic – land‐use change model?

It is commonly recognized that large uncertainties exist in modelled biofuel‐induced indirect land‐use change, but until now, spatially explicit quantification of such uncertainties by means of error propagation modelling has never been performed. In this study, we demonstrate a general methodology to stochastically calculate direct and indirect land‐use change (dLUCandiLUC) caused by an increasing demand for biofuels, with an integrated economic – land‐use change model. We use the global Computable General Equilibrium model MAGNET, connected to the spatially explicit land‐use change modelPLUC. We quantify important uncertainties in the modelling chain. Next,dLUCandiLUCprojections for Brazil up to 2030 at different spatial scales and the uncertainty herein are assessed. Our results show that cell‐based (5 × 5 km2) probabilities ofdLUCrange from 0 to 0.77, and ofiLUCfrom 0 to 0.43, indicating that it is difficult to project exactly wheredLUCandiLUCwill occur, with more difficulties foriLUCthan fordLUC. At country level,dLUCarea can be projected with high certainty, having a coefficient of variation (cv) of only 0.02, whileiLUCarea is still uncertain, having a cv of 0.72. The latter means that, considering the 95% confidence interval, theiLUCarea in Brazil might be 2.4 times as high or as low as the projected mean. Because this confidence interval is so wide that it is likely to straddle any legislation threshold, our opinion is that threshold evaluation foriLUCindicators should not be implemented in legislation. For future studies, we emphasize the need for provision of quantitative uncertainty estimates together with the calculatedLUCindicators, to allow users to evaluate the reliability of these indicators and the effects of their uncertainty on the impacts of land‐use change, such as greenhouse gas emissions.