The sustainability of ecosystem services (benefits people derive from nature) is challenged by global environmental changes. These challenges are especially pronounced in urbanizing agricultural watersheds where changes in land use/cover, management, and invasive species interact. While ecosystem service research is proliferating from local to global scales, understanding patterns and interactions among ecosystem services across heterogeneous landscapes in the context of multiple changing drivers remains limited. This dissertation addresses these knowledge gaps by focusing on the Yahara Watershed in the Upper Midwest of the United States, an exemplar for many agricultural landscapes. It encompasses two general research foci: Chapters 1-3 focus on spatial patterns and interactions among ecosystem services and the role of landscape pattern and human intervention in sustaining the provision of services, using a combination of empirical estimates, biophysical modeling, landscape analysis, and social science; Chapters 4-5 address how biological invasions affect ecosystem functioning and services using a systematic meta-analysis, and field experiment and observations.
Using estimates for the supply of 10 ecosystem services for 2006, we found that most relationships among services were synergies, but tradeoffs occurred between crop production and water quality. Different areas of the landscape supplied distinct suites of ecosystem services, suggesting the importance of managing over large areas to sustain multiple services. Our results also revealed a consistently dominant influence of landscape composition relative to spatial configuration for hydrologic services, identified opportunities for small changes in landscape patterns to produce large gains in surface-water quality, and suggested an overall spatial misfit between policy application and regions of water quality concern in agriculture-intensive regions. Biological invasion also affects ecosystem functions and services. A global meta-analysis showed that invasive alien species affect greenhouse gas emissions by increasing N2O emissions and carbon sequestration. In addition, using field experiment we found that invasion of Asian jumping worms (Amynthas agrestis and Amynthas tokioensis) reduced litter and enriched nutrients in temperate forest and prairie soils. Collectively, this research provides insights into the sustainability of ecosystem services in agricultural landscapes, and informs conservation, management and policy efforts in Midwestern landscapes and other regions experiencing similar environmental changes and sustainability challenges.