The effects of landscape structure and biodiversity on ecosystem services.

Ecosystem services, the benefits that people receive from ecosystems, depend on the movement of organisms and matter across landscapes, as well as the biodiversity and ecosystem functions that are present. Human activities around the world are rapidly and significantly changing ecosystems, landscapes, biodiversity, and, ultimately, ecosystem services. This is particularly true in agricultural systems, where human activities to maximize the ecosystem service of food production often lead to the decline of other important ecosystem services. While we understand that ecosystem services are critical to human well-being, our current knowledge of the provision of ecosystem services across landscapes contains a number of significant gaps that limit our ability to manage for services and human well-being. In particular, we don't fully understand how changes in landscape structure – the composition and configuration of land use types – affect the provision of multiple ecosystem services.In this thesis, I explore the theoretical and empirical relationships between landscape structure, biodiversity, and ecosystem service provision. I first reviewed our current understanding of these links, finding that while we commonly assume that loss of connectivity between habitat patches in a landscape will have negative effects on ecosystem service provision, we have little empirical evidence that this is the case. In particular, we know little about how this landscape connectivity might simultaneously affect multiple ecosystem services, especially for services other than food, pollination, and pest regulation. I then empirically measured the effects of agricultural landscape structure, including forest fragment connectivity, on six ecosystem services in 34 soybean fields in the Montérégie of southern Québec, Canada. Both the isolation of forest fragments on the landscape, and distances within soybean fields from adjacent forest fragments, had significant effects on the provision of ecosystem services. Importantly, each ecosystem service showed distinct differences in its pattern of provision as these components of landscape structure varied. Therefore, landscape heterogeneity, the variety of forest and field types present in the landscape, was critical to ensure the provision of multiple ecosystem services. Investigating pest regulation in this landscape in more detail, I determined that field width and forest fragments are driving patterns of diversity and abundance for both beneficial and pest arthropods in this system. However, these patterns are contradictory between these two arthropod functional groups, resulting in inconsistent effects of landscape structure on pest regulation. Finally, using a simple modeling framework, I explored how changing the pattern of habitat loss across a landscape affects ecosystem service provision at different scales. My model reveals that the form of the relationship between habitat fragments and ecosystem services is critical in determining landscape patterns of ecosystem service provision. In addition, there are inherent tradeoffs between service provision in the agricultural matrix and habitat preservation, as well as mismatches between ecosystem service provision at different scales. However, altering the amount and pattern of habitat loss across the landscape can help mitigate these issues.Overall, my thesis indicates that understanding the connections between landscape structure, biodiversity, and ecosystem service provision will be a critical avenue of research, one that will improve our ability to design multi-functional human-dominated landscapes. Only by understanding how human activities and land use change affect ecosystem services can we generate management tools to maximize multiple ecosystem services at landscape scales. As human demand for ecosystem services and our impacts on natural systems continue to rise, this will be an increasingly important knowledge gap to fill.

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