Supporting Pollinators At The Landscape Scale
Nowadays, most people are very aware of the role that bees play in the pollination of crops, and the decline of bees is a prominent topic across the media. However, the majority of those people only have honeybees in mind, and if you would tell them that there are thousands of wild bee species around, they would be more than just a little surprised.
It, therefore, comes as no surprise that managed pollinators, such as honeybees or bumblebees, are predominantly considered by farmers and beekeepers when thinking about the management of agricultural landscapes. However, wild bees, even though they are not as abundant as the social honeybee, do also play a crucial role in crop pollination, but their protection and rate of decline rarely make it into the mainstream media.
To protect pollination services by managed and wild pollinators alike, agricultural landscapes need to provide sufficient nesting and foraging resources. For managed pollinators, nesting sites are supplied by us – for the social honeybees and bumblebees, we install hives or nest boxes that allow the development of strong colonies. We also ensure abundant foraging resources by placing the colonies close to mass-flowering crops. This not only supports the colonies but also ensures crop pollination.
The picture looks quite different for wild pollinators, comprised of up to hundreds of different taxa in the same area with varying requirements concerning pollen and nectar resources, as well as different nesting strategies (for example, bare soil or nesting cavities).
In heterogeneous landscapes with a mosaic of different semi-natural and natural habitats and a variety of crops, these resources might be available, and agri-environmental schemes, such as sowing flowering strips or planting hedgerows, can further support resource availability. However, in homogeneous landscapes that are often dominated by few mass-flowering crops, forage might only be available for a short time, and nesting resources could be lacking if no natural or semi-natural habitats (forest fragments, hedges or grassland) are available.
The difficulty in supporting wild and managed pollinators in agricultural landscapes is not only in providing sufficient resources for both but actually understanding how we should provide these resources in space and time. This requires the understanding of the life history of the different taxa, including their foraging times, floral resources, nesting requirements, flight distances, and sociality. We then need to implement this knowledge to design agricultural landscapes that are attractive for managed as well as wild pollinators while at the same time fulfilling the increasing need for highly productive crops.
Bees are mobile organisms and, depending on the species, might travel distances between a few hundred meters up to several kilometers to forage. Social bees are usually active for the entire vegetation period, therefore requiring floral resources for a long period of time, whereas different wild bee species are active at different times of the year, and some species are specialized on only a few plant species.
Research on pollination services in agricultural landscapes has intensified over the last few years, spanning pollination efficiency of different bee species, effects of landscape heterogeneity on crop pollination or changes in the pollination of mass-flowering crops in different landscape contexts. However, our research is mostly focused on specific crops, landscapes, or distances between habitat elements, whereas pollinating bees use the entire landscape to different extents and we know little about how they move in the landscape and utilize different resources at varying spatial and temporal scales.
In a recent review on crop pollination at the landscape scale, we propose to combine all these different research aspects with methods such as remote sensing-based quantification of spatiotemporal floral resource and crop rotation dynamics and long-term experimental studies to identify how, within an agricultural landscape, all different elements might either work together or be arranged in such a way that they can provide needed nesting and flowering resources for a high diversity of pollinators.
These findings are described in the article entitled Crop pollination services at the landscape scale, recently published in the journal Current Opinion in Insect Science. This work was conducted by Gesine Pufal and Alexandra-Maria Klein from the University of Freiburg, and Ingolf Steffan-Dewenter from the University of Würzburg.