Projecting Environmental Impacts with varying Population, Affluence, and Technology using IPAT – Climate Change and Land Use Scenarios

We theoretically explore the interrelations between population (P), affluence (A), and technology (T) for various environmental impacts (I), using IPAT-type modelling. To illustrate differences across environmental dimensions, climate and land use impacts were modelled using middle-of-the-road projections for population and per capita income. Different forecasting methods were implemented, including historical extrapolations, models based on stochastic IPAT (STIRPAT), and technological forecasting trajectories in the literature. The different approaches were compared within the IPAT framework. We also explored consequences of alternative trajectories for P, A and T, and we discussed implications for reaching global goals, with a basis in our modelling. Further, our findings were analysed in light of three theories in environmental sociology that give different emphasis on the different components of IPAT. We argue that the large technological mitigation assumed in many forecasts makes affluence and population relatively irrelevant for climate change. However, both factors will likely be influential determinants of land use impact in the twenty-first century.