Natural pest control requires a complete landscape

Abstract: In many studies on landscape and functional biodiversity it is assumed that pest-regulating insects require other habitats than only agricultural fields. Other habitats can e.g. be important as hibernation site, as source of alternative prey or as source of floral resources. The relative contribution of the different habitats to the performance of the beneficial insects and to pest-regulating services they provide is very difficult to study empirically. Landscape-based population-dynamical modelling can then come at hand. Such models can be used to predict mechanisms and patterns that can be tested experimentally. As an example, I created population models of aphid-feeding hoverflies moving between different habitats in an arable landscape. The models are designed and parameterised on the basis of field observations on temporal and habitat-related availability of resources. Habitat-structured models can indicate the optimal composition of the landscape with respect to pest control. The models e.g. indicate that the amount of woody elements, which are particularly important for hoverflies as spring habitat, are a likely a bottleneck for effective pest regulation in Dutch arable landscapes. They also show that various arable crops can enhance each other’s pest control when their aphid populations peek at different moments in time (such as winter wheat and potato). These and other habitats are complementary in their function for the predators, and several of them are needed to create a ‘complete landscape’.