Abstract
Agricultural intensification has led to a widespread decline in biodiversity. The destruction and homogenization of habitats within the rural landscape is arguably one of the main reasons. This has not only affected biodiversity in general, but also ecosystem functions such as natural pest suppression and pollination. The dominant hypotheses on the impact of fragmented landscapes emerge from island biogeography and metapopulation theory. In these theories local populations and biodiversity are maintained by dispersal between patches containing similar habitats. An alternative theory, Landscape Complementation, is based on the observation that some species require different resources during their life history which are not all present in one and the same habitat year round. The presence of various ?complementary? habitats within dispersal or foraging distance is thus essential for the persistence of the populations. Although this concept is well-known among e.g. herpetologist and ornithologists it is not much used in landscape ecology and has yet limited impact on general nature conservation policies. The absence of a proper formalization that allows quantitative predictions, may explain its limited influence in comparison with metapopulation theory. The main objective of the project therefore is to formalize the complementary landscape theory, and to demonstrate its power in predicting the impact of landscape structure on biodiversity and ecosystem services. Our research will focus on well-studied natural enemies of aphids and other insect pests. Many insects responsible for natural pest suppression (such as hoverflies and lacewings) have very different diets as juveniles than as adults (?ontogenetic diet shifts?). While the larvae can often find their prey within annual crops, the adults need to move to field margins or other non-crop habitats to find the floral resources they feed on. In autumn, winter and spring arborous habitats are required to provide food and shelter. Consequently, individuals have to move from habitat to habitat depending on their life stage, their feeding condition and on the spatio-temporal availability of resources. The impact of habitat configuration on population persistence and prey suppression will be analyzed by stage- and habitat-structured population models specified for these species. The models will be validated by comparing its predictions with data on species distributions. When validated the models can be used to design and manage non-crop habitats that optimally support biodiversity and natural pest control in agriculture-dominated landscapes.
Netherlands