Biological Pest suppression Potential in Europe

Since the 1940ies increased agricultural production has modified agricultural landscapes, including destruction and fragmentation of natural habitats, reduction in habitat diversity, and increases in habitat disturbance and agrochemical application. Agricultural intensification is considered a major driver of global biodiversity loss, and has important effects on many ecosystem services. Much recent research has focused on valuating and mapping ecosystem services at various spatial scales, but predictive models that explicitly address how land-use affects ecosystem services mediated by biodiversity are rare. Biological pest control is one ecosystem service threatened by agricultural intensification. In this proposal, a consortium of three teams will explore the relationships between biodiversity, as mediated by agricultural land-use at different scales, and the structure, diversity and variability of natural enemy-pest-alternative prey food web interactions and the value of biological control. Our study system will be cereal aphids, which are among the economically most important insect pests in many parts of Europe, and the most important groups of natural enemies of these aphids as well as their non-pest food sources. Based on the vast amount of data already collected by our team we will analyse how local land use and landscape composition affects natural enemy community composition and how historic shifts in natural enemy communities affect biological control. Using up-to-date molecular techniques, food web interactions will be empirically examined under field conditions allowing us to conduct interaction network analyses to investigate how land-use at different scales affects trophic linking and biological control. These data will feed into a model for biological control of cereal aphids, and facilitate valuations of biological control through monetary and non-monetary methods. Finally, we will map biological control across landscapes in Europe and test how different future land-use scenarios of changed agricultural intensity and landscape structure will influence biological control.

APPEAL, a research project jointly conducted between research teams from Austria, Germany and Sweden, has in detail investigated how changes in land use affect predator communities, food-web interactions and biological control of cereal aphids and explored how biological control can be valuated and considered in relation to insecticide application. In both an empirical and a modelling study we found a strong effect of landscape complexity on predator community composition and biological control potential, with complex landscapes with small fields and large proportions of grasslands having more effective biological control. The composition of functional traits in the predator community was found to be a strong predictor of biological control, with the relationship between predator and prey body size seeming to be a particularly important predictor. Food-web interactions were explored using molecular gut content analysis, an expertise specifically provided by the Austrian sub-project. A replicated field experiment showed that albeit the occurrence of weeds in cereal fields do not affect arthropod predator community composition, they induce significant and immediate changes in trophic interactions and thereby affect the functional role of natural enemies. The increased habitat heterogeneity created by weeds leads to more resilient food web interactions and thus a more robust pest control function of generalist predators. We have also developed a spatially explicit model to predict biological control services across agricultural landscapes. When applied to two Swedish regions, the model suggests that natural enemies will reduce crop damage caused by aphids with 45-70% depending on landscape complexity. Our analysis of risks, risk perceptions and cost structures has shown that under the current conditions insecticide use is an inevitable rational decision of farmers. Increasing insecticide prices by an order of magnitude would change the calculus, but lead to higher risks in pest control.