Models have been widely used in agricultural science to understand complexity, predict the consequence of change and extend knowledge to new scales. ‘Crop modelling’ began in the 1960s and is now well advanced and applied globally, but is restricted to a few economic species. More recently, modelling has been expanded to cover biota as mediators of ecological process or as end-points for assessment of environmental status. This chapter looks at the range of modelling in biodiversity studies, including individual-based approaches that combine within- and between-species diversity, process-based models operating at plot, field and increasingly at landscape scales, integrated system models that seek optimal trade-offs between biodiversity and economic outputs, and global frameworks that combine the biophysical, economic, social and political forces acting on biodiversity. The chapter concludes with a more practical approach known as multi-attribute decision modelling that can be worked and applied by biodiversity managers and planners.