Effects of created habitats on farmland biodiversity

Abstract: Agricultural intensification has caused severe declines among biodiversity in European farmland over the last half century. The transformation of the agricultural landscape has led to reduced availability of key resources such as food, nesting habitat and shelter. In this thesis I have investigated a way of ameliorating the negative effects of agricultural intensification, through the creation of wildlife habitats. I have also studied the effects of organic farming and increasing the amount of ley in the landscape as means to reduce farming intensity. I have tested the effects of these interventions in different landscape contexts, on a range of biodiversity, and at different spatial scales. I found that sown flower strips were able to increase abundances of bumblebees across the landscape, i.e. outside of the created habitat itself. An important finding that demonstrates that created habitats can generate real increases in abundance and do not simply redistribute organisms as a response to attractive food patches. A similar result was found for seed-eating passerines in winter, the density of which was increased in landscapes that contained wild bird cover. The effect was only evident within the 250 m closest to the wild bird cover, but it was not caused by an attraction of birds from the surrounding landscape, at least not at intermediate scales. The effect was also consistent through the survey period, in mid- to late winter. Created habitats did not seem able to increase abundances of three game species (grey partridge, common pheasant, brown hare). There may be several reasons for this relating to the quantity and quality of the habitats created, but also to other factors that were outside the scope of these studies, such as predation and reduced genetic quality. Instead I found a strong negative effect on hares of the amount of ley within the landscape, which could be caused by higher mortality among leverets in ley fields. Organic farming appeared positive for hares but only in landscapes with high crop diversity. My understanding of this is limited but I offer some speculative explanations. Although a high level of biodiversity is generally positively related to landscape heterogeneity, I found no clear effects of landscape heterogeneity on the organisms studied. To conclude, I found that created habitats have the potential to be multi-functional and benefit several organism simultaneously. The specific requirements of different organisms as well as local conditions must however be considered when drawing up a conservation plan. More research into the design and implementation of interventions is necessary to ensure conservation is based on rigorous scientific evidence.