Small fields have big benefits for pollinators – but only with semi-natural habitats nearby

Pollinators, such as bumblebees, are essential providers of ecosystem services for agriculture, yet their numbers are declining due to landscape structure simplification and habitat loss.

To explore this issue, an international research group led by Riho Marja set up 56 commercial bumblebee colonies in Eastern Austria and Western Hungary—two regions once divided by the Iron Curtain and now markedly different in field size: Austria with very small, narrow fields (around 2 hectares) and Hungary with large fields (around 17 hectares). At each site, colonies were placed next to either winter cereal fields or mass-flowering oilseed rape, and either close to or far from semi-natural habitats such as forest patches, hedgerows, river margins, or low-intensity managed grasslands.

Their goal was to find out how local factors (crop type) and landscape-scale features (mean field size and proximity to semi-natural habitat) affect colony success—specifically traffic rate (a proxy for bumblebees activity), growth, and reproduction. They also examined pollen diversity and tested bumblebee navigation abilities by relocating workers and recording how quickly they returned to the colony, using small radio frequency identification tags.

Their results showed that proximity to semi-natural habitats and oilseed rape fields boosted bumblebee activity and colony performance. Colonies near both oilseed rape and semi-natural habitats had higher traffic rates, grew faster, and produced more queen brood cells.

Semi-natural habitats also improved bumblebee orientation. Bees returned to their colonies faster when these habitats were nearby—especially when flower diversity was high. In contrast, colonies far from such habitats had slower return times, likely due to fewer visual navigation cues.

Interestingly, small field size improved navigational efficiency even when flower species richness was low. This may seem counterintuitive, but the authors believe that the dense network of field edges in such landscapes makes orientation easier—even without a high diversity of flowers.

Bumblebees did not rely solely on the most abundant flowers. In fact, they often preferred pollen from wild bushes, trees, and herbs in semi-natural habitats over the more abundant oilseed rape. While oilseed rape supported colony growth, more than 80% of pollen collected came from wild plants such as Acer and Prunus species.

This study shows that small fields are important for pollinators, but they are not a stand-alone solution. Their benefits depend on the presence of nearby semi-natural habitats, which provide diverse, season-long food resources and aid navigation. In large-scale farming landscapes, restoring or maintaining semi-natural habitats is even more critical. Without them, even mass-flowering crops like oilseed rape cannot fully compensate for the lack of food resources across the season.

The study findings suggest that smart landscape design—not just crop choice—is crucial for supporting pollinators. Semi-natural habitats and small-scale farming systems work best when combined, creating a truly pollinator-friendly environment. For farmers, the recommendation is clear: combine small field structures with patches of semi-natural habitat to maintain healthy pollinator populations and the vital ecosystem services they provide.