Biodiversity and ecosystem services: pollination, biological control, and nature conservation in agricultural landscapes

Agriculture has done more damage to nature than any other human activity, and yet food production could need to be doubled by the middle of this century. As agricultural land is expanded and intensified, critical thresholds in the loss of natural habitats are crossed. This loss of non-crop habitats can have negative feedback on crop production, because it can cause a loss of “ecosystem services” that support and regulate crop production, such as the pollination of crops by bees and the biological control of crop pests by their natural enemies. Because of this connection between non-crop habitats and crop yields, there could be potential for habitat conservation to benefit both agriculture and nature. The research in this thesis focuses on pollinators and natural enemies, because these species constitute a vital connection between food production and biodiversity conservation. Could habitat management be used to conserve both pollinators and natural enemies in agricultural landscapes? Will the relationships between pollinators, natural enemies, and natural habitats change with climate change? Where should we prioritize the resolution of conflict between agriculture and nature, and how? This thesis addresses these questions through literature review and meta-analysis, geographic information systems (GIS) and hotspot analysis, field research on the distributions of trap-nesting bees and wasps on environmental gradients, and laboratory research on the development of bees and wasps at high temperatures. This thesis suggests that it might be possible to conserve communities of both pollinators and natural enemies, in general, by means of habitat management, but it might not be possible to conserve specific combinations of pollinators and natural enemies, which might have opposite responses to some forms of environmental change, such as global warming. This thesis also suggests that the resolution of conflict between agriculture and nature should be prioritized in sub-Saharan Africa, and it outlines a conceptual framework for systematic conservation planning in agricultural landscapes.