From a policy point of view, the rapid loss of biodiversity (how ever measured) constitutes an urgent need to improve the ability to forecast possible changes in biodiversity. Scenario development and modelling are essential tools for studying changes of biodiversity and their impacts in order to provide well-founded policy options. However, so far no comprehensive model has been developed integrating the diverse relevant ecological, economic, individual and societal processes. Instead socio-economic, climate and biodiversity models exhibit a wide range of assumptions concerning population development, economic growth and the resulting pressures on biodiversity. The paper summarises the efforts undertaken in the framework of the ALARM project by an interdisciplinary team of economists, climatologists, land use experts and modellers. It describes the challenges of such a kind of work, bringing together different world views unavoidably inherent to the different fields of investigation.