Applied ecosystem modeling makes use of a range of approaches to analyze and assess environmental problems and their potential solutions.  Some modeling approaches have been developed with specific applied problems in mind, while others were developed as basic science tools and later used for applied questions and concrete issues in management, decision-making, policy, or sustainability science.  An ecosystem model is one that, at its foundation, represents the cross-scale linkages among ecosystem processes such as production, decomposition, nutrient cycling, carbon balance, water budgets, and ecophysiology.  These models sometimes also include species dynamics or population-community level processes.  These models have long been used as tools for synthesis and investigation in basic ecology:  25 years ago, the ecosystem concept was voted by the members of the Ecological Society of America as the single most important concept in ecology.  The past few decades have seen a proliferation in the creation and application of ecosystem models.  Applications include nutrient eutrophication and “dead zones,” invasive species, acid rain, carbon sequestration, control of predator populations, the effects of climate change, forest management for timber or C storage, fisheries, function of riparian zones, wetland management and nutrient retention, and others.  A recent and exciting development is the linking of ecosystem processes to social and economic processes in the modeling of social-ecological systems to address applied environmental problems such as habitat loss or the provision of ecosystem services in this broader interdisciplinary framework.