THE ROLE OF LANDSCAPE IN MEDIATING BIODIVERSITY AND ECOSYSTEM SERVICES TO AGRICULTURE
Currently more than 40% of earth’s terrestrial surface is devoted to agriculture and continued agricultural expansion and intensification is the leading cause of biodiversity loss worldwide. Yet, many of the services upon with agriculture relies, such as biological pest control and pollination, are provided by diverse communities of beneficial insects. Several studies have documented declines in the diversity and abundance of pollinators and natural enemies in landscapes with high agricultural cover. However, we lack a framework for predicting which species are most threatened by agricultural intensification and which are likely to persist. Additionally, studies documenting negative effects on ecosystem services and crop yield have been rare. Therefore the ecological but also the economic impact of land use intensification remains unclear. Here, I investigate the effects of landscape simplification due to agricultural intensification on both pollinator and natural enemy communities providing services to fruit farms in New York State. In each study, I evaluate effects on community composition, ecosystem service delivery and ultimately crop yield. My results reveal that landscape simplification is associated with a loss in abundance, species richness and functional diversity from beneficial insect communities. Loss of species from communities was not random but rather mediated by traits that are often similar among closely related species. As a result the evolutionary history represented within communities in highly agricultural landscapes was 200 million years less than communities in more diverse landscapes. For bees, functional and phylogenetic diversity better predicted pollination services and crop yield compared to species richness alone. Overall, both pollination services and biological control were negatively influenced by agricultural intensification. However, I also explore one landscape and one local scale strategy to recover community diversity and ecosystem services. At the landscape scale, a diversity of crops emphasizing complementarity in bloom time can promote spillover of pollinators from mass flowering crops like apple into consecutively blooming crops such as strawberry. At the local scale, wildflower plantings bordering crops can support diverse pollinator communities but were most effective when implemented in landscapes with intermediate cover of natural habitats. Importantly, pest populations were higher in plantings with an adjacent wildflower border at sites with the least and most natural habitat cover. Wildflower planting did little to enhance biological control of pests. These findings indicate that local habitat enhancements can have costs, but by targeting locations for establishment these costs can be minimized. By understanding the ecology agricultural ecosystems, we can conserve biodiversity while at the same time promoting crop productivity.
Agriculture; Wildlife conservation; Ecology
Loeb, Gregory M
Danforth, Bryan N; Poveda, Katja A
Ph. D., Entomology
Doctor of Philosophy
dissertation or thesis