Impacts of agri-environment schemes for landscape connectivity of UK butterflies

Agriculture represents a significant driver of biodiversity declines globally, threatening species through land use change and intensification. The spatial configuration of remaining natural habitat can have further implications for species if habitat fragments are highly isolated from one another, impeding dispersal. Agri-environment schemes (AESs) have become the principal means of conservation on farmland across Europe, and in this thesis I examine whether AES management options provide connectivity benefits to species within fragmented agricultural landscapes. Focusing on butterfly species within England, UK, and the common AES option of setting-aside field margin strips at the edges of agricultural fields, I examined connectivity impacts of AES management in three ways. Firstly, I examined the movement of butterflies through field margin strips to identify whether habitat enhancement had implications for movement parameters such as speed and efficiency. I found that enhancement with nectar resources boosted local abundance without reducing speed or efficiency. Secondly, I used metapopulation models to examine potential impacts of field margin strips on landscape scale range expansion and metapopulations persistence. I found that field margin strips improved range expansion for some but not all species types, that optimum placement of field margins depended on species traits, but that field margins have very little impact on overall metapopulation persistence. Finally, I used butterfly occurrence records over ~10-15 years of AES implementation to empirically test the effects of field margins on local colonisations and extinctions. Field margin set-asides increased colonisation and decreased extinction probabilities, but only for a minority of margin-dwelling butterflies. Overall, I have found that AESs offer some connectivity benefits, but that responses to AESs are species-specific. Therefore, conservation planning should carefully consider the suite of species for which connectivity benefits are sought, because AESs are unlikely to provide connectivity benefits for rare species in most need of conservation action.