D3489: Influences of climate, landscape and weather on the occurrence of native pollinators

Pollinators provide critical ecosystem services in both natural and agricultural ecosystems. Delivery of these services depends on the ability to develop, survive, and move through the environment, but a changing climate means this community is potentially vulnerable to disruption. Fluctuations in weather can disrupt development, impede movement, and affect survival, while long-term climate norms influence environmental niches and influence species distribution. Landscape composition also influences beneficial insect distribution and has the potential to reduce the impacts of climate change. Here we use a database of more than 100,000 bee occurrence records, collected from 320 sampling sites across a 90,000+ km² area to generate models of species occurrence for 50 bees. We use a tree-based machine learning method with extreme gradient boosting to create predictive classification models. These models are then used to analyze the relative importance of weather, climate, and landscape variables. We found that climate and landscape variables have the highest importance for bee species, and the variables with the highest mean absolute importance are cumulative degree days, cumulative precipitation, and percent tree cover. When we analyzed individual species models, bee taxonomic groups respond similarly to climate and weather, but not landscape. These results indicate that pollination service supply is largely determined by climate factors, but that there are some species whose occurrence can be influenced through changes to the landscape.