Linking biodiversity, landscape dynamics and agricultural policies to inform conservation on farmland: The case of Mediterranean farmland birds

About half the world's terrestrial surface is managed for agriculture, and an important proportion of global biodiversity is found on farmland. Therefore, conserving biodiversity on farmland is an essential element of worldwide efforts for reversing global biodiversity decline. However, this goal has been hindering by the pervasive intensification of farming practices, which have contributed to an increase in the rate of biodiversity losses during the last decades. Furthermore, managing farmland landscapes to enhance biodiversity is complex, as biological diversity is constrained by a number of interacting and changing socioecological factors including agricultural policies, socio-economic drivers and biophysical conditions, which may affect the effectiveness of conservation actions. This thesis addresses these issues using three case studies focusing on breeding bird assemblages living in Mediterranean farmland landscapes of southern Portugal. This model system was used to understand how biological diversity may vary in space and time in relation to landscape dynamics, agricultural policies and conservation actions, which is a knowledge required to inform conservation actions on farmland. The studies focused on (i) how to enhance the effectiveness of conservation investment in farmland protected areas; (ii) how to manage farmland landscapes for biodiversity conservation within and outside protected areas; and (iii) how to link biodiversity measures to landscape features to inform conservation actions and agricultural policies. These studies provided insights to the design and evaluation of conservation actions by showing that enhancing the effectiveness of conservation investment in farmland protected areas may require a greater focus on the wider biodiversity in addition to that currently devoted to flagship species, as well as improved matching between conservation and agricultural policies. Also, it was shown that managing farmland landscapes for conservation needs to consider both composition and heterogeneity, and that maximising the prevalence of biodiversity-friendly crops may be particularly important in landscapes where a range of species of conservation concern is strongly associated with the production component of the landscape. Finally, it was shown that the analyses of spatial variation in species composition (beta diversity) is required to understand the impacts of agricultural policies and conservation actions on farmland biodiversity, as it provides information on how changes in landscape heterogeneity affects local (alpha diversity) and regional (gamma diversity) species richness and composition. However, it also highlighted the need to evaluate beta diversity changes against specific conservation goals. Overall, this thesis provides novel information on the drivers of biodiversity change in agricultural landscapes, showing in particular the cascading effects that may xii FCUP Linking biodiversity, landscape dynamics and agricultural policies to inform conservation on farmland occur from agricultural policies through landscape dynamics to alpha, beta and gamma diversity patterns, which in turn may be used to improve biodiversity conservation and management on farmland.