Environmental processes support human well-being by a number of goods and services, commonly referred to as ecosystem services. Since these services are not included in market prices, suboptimal decisions (e.g., on land use systems) result. An analysis of the trade-offs between market goods and ecosystem services can be used to achieve better-informed decisions. Including biophysical process into the trade-off analysis allows for a greater flexibility as well as for an increased reliability of the results of these trade-off analyses. We introduce the most important concepts of environmental modeling and show how these concepts can be used to study ecosystem service trade-offs using the example of an agricultural watershed in southern Maryland, USA. We study how land use can be optimized for this region. The multifunctionality of the landscape is reflected in multidimensional performance criterion based on crop yield, fertilization costs, and water quality issues. We varied the shadow prices for water quality and studied the effects on optimal land use patterns. In a second step, we analyzed trade-offs between crop yield, water quality, and other ecosystem services. The results indicate nonlinearity in some of the trade-offs.