As of the year 2000, 40% of Earth’s ice-free land area is being directly used by humans, and an additional 37% is surrounded by human-modified areas. Land-use change, along with other human-induced global change drivers, are accelerating the rates of extinction of most taxa. Researchers are beginning to experimentally investigate how these changes in biodiversity affect ecosystem services, such as water purification, climate regulation, and food production, but do not yet understand the effects of species loss in real ecosystems. Pollination is a critical ecosystem service and relies upon multiple species of pollinators. My proposal aims to understand the threats to the pollinator species that provide this critical ecosystem function and assess the consequences of their decline in real ecosystems. Research about the functional consequences of biodiversity is dominated by small-scale experimental studies. These experiments have manipulated diversity by assembling random subsets of species drawn from a common pool of taxa. This approach is useful for understanding the theoretical consequences of diversity loss but is unrealistic in the sense that it assumes species can go extinct in any sequence over time. Extinction, however, is generally a nonrandom process with risk determined by life-history traits such as rarity, body size, and sensitivity to environmental stressors. The importance of biodiversity loss on the production and stability of ecosystem services will depend, then, on which bee species are lost, and which species are well-adapted to anthropogenic habitats. I will investigate this relationship by developing a framework that goes beyond aggregate biodiversity measures and takes into account trait functional diversity, species specific responses, and community structure. I will use new synthetic analysis of existing datasets form Europe and US, and long-term monitoring of experimentally manipulated natural communities in southern Spain.