Ecology and conservation of pollinators in forest and agricultural landscapes

Pollinators are essential for the reproduction of wild and cultivated plants, significantly contributing to the stability of ecosystems, and to the well-being of humans. However, anthropogenic changes in the land use and in the management intensity of agricultural and forest landscapes have resulted in the degradation of habitats important for pollinators, with negative consequences on their diversity and abundance. Considering pollinators’ fundamental functions and services, and the alarming reports of their decline, there has been an increasingly higher emphasis in their conservation at different levels. Often, the focus of pollinator conservation has been the management of agroecosystems, while the management of forest processes have seldom been included in large-scale conservation strategies. Throughout the chapters of this thesis, I aimed to explore which conservation opportunities exist in degraded agricultural and forest landscapes and how can these be integrated in a multifunctional landscape with different land management objectives, to prevent negative impacts on valuable ecosystem services caused by pollinators’ decline. First, I explored the effects of large-scale environmental perturbations in productive forest landscapes on the diversity of pollinators, concluding that windthrow gaps have positive effects on the diversity of pollinators, although pollinator communities experience high temporal changes as the disturbed habitats evolve in the ecological succession (Chapters 1 and 2). Second, I assessed the potential of forest restoration in intensively managed agricultural landscapes in sustaining pollinator communities, finding promising outcomes of forest restoration (Chapter 3). Third, I explored pollination as an ecosystem service, contributing to the quantification of the biological and socio-economic impacts of pollinator loss in degraded landscapes on the quality of globally important crops. Results indicated that pollinators strongly improve several commercially important attributes related to appearance and shelf life, stressing the urgency of safeguarding pollination services to maintain food security (Chapter 4). Fourth, I focused on how to reconcile two contrasting land management objectives, i.e. insect conservation and insect pest control, proposing complementary approaches to combine multiple diversification strategies at the landscape scale, taking advantage of the synergisms between two land management objectives (Chapter 5). Fifth, I explored the potential of indicators for pollinator diversity to ease monitoring and aid the evaluation of conservation actions targeting pollinators. Results showed that the total abundance of wild bees is a strong predictor of wild bee species richness across different climates, habitats, and sampling methods, encouragingly advancing the evaluation of many local and regional conservation initiatives (Chapter 6). In conclusion, the results obtained from this thesis suggest that the design of heterogeneous and multifunctional landscapes not only can support the diversity of pollinating insect, but it appears to be compatible also with the mitigation of insect outbreaks and with other land management objectives, such as quality agricultural production. Overall, my PhD work contributed to emphasise the need for a holistic approach when planning the land use.