Scale-dependent mitigation of pollination – winners and losers

Abstract

Ongoing agricultural intensification and landscape simplification pose a threat to wild pollinators and the pollination service they provide to both crops and wild plants. As a result, there is currently a strong focus on how to benefit pollinator populations in agricultural landscapes, by e.g. preserving semi-natural habitats or providing supplemental flower resources in the form of flower strips. However, not all pollinators are the same, neither in terms of how they react to landscape change and mitigation measures, nor in what services they provide. Using recent research in our group, we demonstrate the implication for pollinators and pollination. We demonstrate how both nesting habitat availability and spatio-temporal availability of food resources act as spatial ecological filter for bees, explaining variation in community composition along a landscape complexity gradient. In field-studies we show that the spatial scale at which pollinators react to mitigation measures is dependent on their functional type. However, as demonstrated by experiments manipulating densities of honey bees, the presence of some pollinator species may be impacted by the density of other species. Hence, to understand pollinator community composition, we need to focus not only on how land-use change affect individual pollinator species, but how it modifies scale-dependent interaction between species. Using a novel modelling approach based on foraging theory, we demonstrate that the coexistence of multiple pollinator species may be critically dependent on the spatial structure of landscapes. Thus, landscape simplification may be detrimental to some species, because of the interaction with species that are better able to utilize spatio-temporally variable resources. This may explain our results that a wild flower species pollinated by generalist pollinators benefit from oilseed rape at landscape scales, while a wild flower species relying on more specialized pollinators does not. We discuss our results in relation to where and when pollinator mitigation measures should be implemented to preserve pollination as a service.