Native habitat mitigates feast–famine conditions faced by honey bees in an agricultural landscape

Significance

Industrial-scale production of crops through monocultures has resulted in “green deserts” of reduced biodiversity in many areas worldwide. Such simplified landscapes may impact ecosystem services such as pollination. Here, we present a large-scale, longitudinal study of managed honey bee colonies in the context of corn and soybean monocultures. Our results reveal a brief burst of colony growth during soybean bloom, followed by a longer period of forage dearth, resulting in decline in several aspects of honey bee health at both colony and individual levels. We demonstrate this decline is reversible when honey bees have access to native, perennial plants (i.e., prairie). Our results suggest sustainable pollinator management in landscapes dominated by monocultures can be achieved through reintegration of native biodiversity.

Abstract

Intensive agriculture can contribute to pollinator decline, exemplified by alarmingly high annual losses of honey bee colonies in regions dominated by annual crops (e.g., midwestern United States). As more natural or seminatural landscapes are transformed into monocultures, there is growing concern over current and future impacts on pollinators. To forecast how landscape simplification can affect bees, we conducted a replicated, longitudinal assessment of honey bee colony growth and nutritional health in an intensively farmed region where much of the landscape is devoted to production of corn and soybeans. Surprisingly, colonies adjacent to soybean fields surrounded by more cultivated land grew more during midseason than those in areas of lower cultivation. Regardless of the landscape surrounding the colonies, all experienced a precipitous decline in colony weight beginning in August and ended the season with reduced fat stores in individual bees, both predictors of colony overwintering failure. Patterns of forage availability and colony nutritional state suggest that late-season declines were caused by food scarcity during a period of extremely limited forage. To test if habitat enhancements could ameliorate this response, we performed a separate experiment in which colonies provided access to native perennials (i.e., prairie) were rescued from both weight loss and reduced fat stores, suggesting the rapid decline observed in these agricultural landscapes is not inevitable. Overall, these results show that intensively farmed areas can provide a short-term feast that cannot sustain the long-term nutritional health of colonies; reintegration of biodiversity into such landscapes may provide relief from nutritional stress.