Impacts of agricultural land-use change on bees.

Over the past few decades, reports have highlighted declines in insect pollinators, particularly bees. This is concerning given they are crucial pollinators of many wild and crop plant species. Evidence suggests that agricultural intensification is associated with these declines (Potts et al. 2010), but the specific driving factors remain unclear.Agricultural landscapes often consist of extensive non-flowering fields that are likely to limit food resources or fields that consist of flowering crops that tend to be planted as monocultures, which whilst providing nutrition can lack diversity (compared with wildflowers). Furthermore, they are only available for temporary blooming periods and are often treated with pesticides (Raine & Gill 2015). Social bees are recognised as one of the most important groups of insect pollinators, so it is important to understand how variation in spatial and temporal nutrition availability across a landscape affects colony development and fitness.

1. How does temporal variation in nutrition combined with pesticide exposure affect bumblebee colony development at different stages of their life cycle? Are there windows of susceptibility at certain colony stages?
We will manipulate the pollen quantity provided at different phases of the colony life cycle, simulating the bloom and bust of flowering crops in an agricultural environment. We will expose colonies to a pesticide via food, which simulates contaminated food being brought back to the colony. To understand how the interactions between changes in nutritional availability and pesticide exposure affect colony development, we will monitor the development using a number of methods. To specifically investigate whether colony fitness is affected, we will look at the number of sexuals produced (males and queens). 2. How does pesticide exposure affect bumblebee foraging dispersal distances? How does this affect their ability to exploit the patchiness of floral resources that can be found across wider agricultural landscapes? We will use a system of flight mills to measure bumblebee flight performance, assessed by monitoring speed, distance and periodicity of the flights of individuals exposed to pesticides. This can be used to inform dynamic spatial models to better understand how variation in resource distribution surrounding a nest (bumblebees are central place foragers) may limit the amount of food that foraging can bring back to the nest (this underpins colony development). With an understanding of how bumblebees respond to the distribution and spatial-temporal dynamics of food resources and pesticide exposure, we can start to make predictions about colony success in varying landscape settings. 3. Can we project potential spatial distribution of bumblebees across the UK?
One goal is to be able to map hazards to pollinators across large geographical space. We intend to use mapping and established modelling tools to predict if certain land cover can support bumblebees, based on proxy measures of foraging resources, the timing and duration of resource availability, and the distance between resources and the nest. The amount of potential foraging resources can be estimated using land cover and crop maps covering the UK, developed by the Centre for Ecology and Hydrology. Our model outputs can also be validated against field observations of pollinator abundance and richness in various landscape settings across the UK.
The outputs of this research will provide insights into complex plant-pollinator dynamics and how these are being affected by agricultural practices. This can help to inform policies and land management strategies on how to better plan supportive landscapes for insect pollinators.
References: Potts, S.G. et al., 2010. Global pollinator declines: Trends, impacts and drivers. Trends in Ecology and Evolution, 25(6), pp.345-353.
Raine, N.E. & Gill, R.J., 2015. Tasteless pesticides affect bees in the field. Nature, 5