We Can’t Keep Winging It: Evidence for the Drivers of Declines and Conservation Interventions for Pollinators

Pollinator declines are a widely recognised global threat due to their role in agriculture and non-agricultural plant biodiversity. These declines are associated with habitat degradation and fragmentation, agricultural intensification, pesticide use, emerging diseases and climate change. These declines urgently require conservation interventions and policy responses. However, to be successful conservation interventions and policy responses need to be implemented with an adequate evidence base, including evaluations of the drivers of declines, conservation interventions and monitoring tools.
The work presented in this thesis focuses on providing evidence for pollinator conservation. Specifically, providing evidence for emerging diseases as a driver of declines, citizen interventions as conservation measures, and the driver of pollinator communities as well as a comparison of the analytical tools used to assess pollinator communities. In the introductory chapter I provide an overview of the literature relating to the importance of pollinators, the declines of pollinators, the drivers of these declines and the potential interventions for declines. Further, I consider the pertinent literature surrounding the subsequent four chapters, including the use of protected areas, the phenomena of pathogen spillover and extent in pollinators, and the use of citizen interventions for pollinator conservation. Chapter 2 provides an overview of the methods used within the subsequent four chapters.
Chapter 3 investigates the effects of landscape level and habitat quality factors on pollinator communities present in protected calcareous grasslands. This chapter uses two analyses and varying scales of assessing pollinator communities to understand the effects of drivers of pollinator communities. Here, floral species richness increased the abundance of butterflies and the species richness of hoverflies. Further, limited landscape quality effects were found. However, the use of hierarchical modelling of species communities showed species level response to habitat quality and landscape factors.
Chapter 4 presents the extent of pathogen spillover of the honeybee virus, DWV-B, to wild bee species was assessed in important, often protected, grassland landscapes. The extent of pathogen spillover was assessed and the drivers of the likelihood of pathogen spillover were also considered looking at both pollinator communities present and landscape quality. Here, pathogen spillover was found to occur in 32 grassland sites across five countries in four bee species. The likelihood of infection and viral load in wild bees was found to be driven by the prevalence and viral load of DWV-B in honeybees, respectively. Further, the abundance of bumblebees was positively correlated with prevalence in wild bees, however, negatively correlated with viral load.
Chapter 5 and 6 focus on the potential for altered mowing frequency as a citizen intervention for pollinators. Both chapters investigate the capacity for reduced mowing in summer to increase floral resources available and subsequently increase pollinator abundance. Chapter 5 uses a national scale study based in gardens. Chapter 6 uses the UK Ministry of Justice prison and court system as a case study for urban and semi-urban building parks. Both chapters find positive effects on floral resource availability and pollinator abundance of reduced mowing.
The final discussion (Chapter 7) explores the key findings of the thesis as a whole and discusses their implications for pollinator conservation. As well as discussing the future directions from the prior chapters required for the conservation of pollinators.