This is a central chapter of the book, providing an overview on approaches to link ecology and economics in models, again using examples from the literature. The first sections focus on links between the ecological and economic system components that can lead to coupled ecological-economic dynamics. In the following sections it is argued that the consideration of these dynamics only focuses on the supply side of biodiversity which, among other things, addresses the question of how biodiversity can be conserved cost-effectively. Of equal importance, however, is the demand side that concerns the values humans attach to biodiversity. Two different approaches for the integration of supply and demand sides are outlined, which allow for an analysis of the efficiency of biodiversity conservation policies and strategies.