Dryland Organic Farming Partially Offsets Negative Effects of Highly Simplified Agricultural Landscapes on Forbs, Bees, and Bee-Flower Networks

Diversified Farming in a Monoculture Landscape: Effects on Honey Bee Health and Wild Bee Communities

In the last century, a global transformation of Earth's surface has occurred due to human activity with extensive agriculture replacing natural ecosystems. Concomitant declines in wild and managed bees are occurring, largely due to a lack of floral resources and inadequate nutrition, caused by conversion to monoculture-based farming. Diversified fruit and vegetable farms may provide an enhanced variety of resources through crops and weedy plants, which have potential to sustain human and bee nutrition. We hypothesized fruit and vegetable farms can enhance honey bee (Hymenoptera: Apidae, Apis mellifera Linnaeus) colony growth and nutritional state over a soybean monoculture, as well as support a more diverse wild bee community. We tracked honey bee colony growth, nutritional state, and wild bee abundance, richness, and diversity in both farm types. Honey bees kept at diversified farms had increased colony weight and preoverwintering nutritional state. Regardless of colony location, precipitous declines in colony weight occurred during autumn and thus colonies were not completely buffered from the stressors of living in a matrix dominated with monocultures. Contrary to our hypothesis, wild bee diversity was greater in soybean, specifically in August, a time when fields are in bloom. These differences were largely driven by four common bee species that performed well in soybean. Overall, these results suggest fruit and vegetable farms provide some benefits for honey bees; however, they do not benefit wild bee communities. Thus, incorporation of natural habitat, rather than diversified farming, in these landscapes, may be a better choice for wild bee conservation efforts.

Pan Traps for Tracking Honey Bee Activity-Density: A Case Study in Soybeans

To study how honey bees utilize forage resources and guide pollination management plans in crops, a multitude of methods have been developed, but most are time consuming, costly, and require specialized skills. Colored pan traps for monitoring activity-density are a simple, efficient, and cost-effective alternative; however, their usefulness for studying honey bees is not well described. We examined if trap color, location within a field, and the presence of managed colonies affected estimates of honey bee activity-density within soybean fields. Soybeans are visited by pollinators but do not require these visits for seed development. Pan traps, especially those colored blue, captured more honey bees when colonies were present. There were no differences in activity-density based on placement of traps within a field nor with increasing distance from colonies. Throughout the season, activity-density in soybeans was constant but tripled after soybean ceased blooming, suggesting spikes in pan trap captures may indicate periods of forage scarcity. Activity-density did not correlate with the population size of worker bees at a site, but did correlate with number of colonies present. We conclude that pan traps can be useful for assessing honey bee activity, particularly for estimating colony presence and identifying times of forage scarcity.

Impacts of Agricultural Management Systems on Biodiversity and Ecosystem Services in Highly Simplified Dryland Landscapes

Covering about 40% of Earth’s land surface and sustaining at least 38% of global population, drylands are key crop and animal production regions with high economic and social values. However, land use changes associated with industrialized agricultural managements are threatening the sustainability of these systems. While previous studies assessing the impacts of agricultural management systems on biodiversity and their services focused on more diversified mesic landscapes, there is a dearth of such research in highly simplified dryland agroecosystems. In this paper, we 1) summarize previous research on the effects of farm management systems and agricultural expansion on biodiversity and biodiversity-based ecosystem services, 2) present four case studies assessing the impacts of management systems on biodiversity and ecosystem services across highly simplified dryland landscapes of the Northern Great Plains (NGP), USA, 3) discuss approaches to sustain biodiversity-based ecosystem services in drylands, and 4) present a conceptual framework for enhancing agricultural sustainability in the drylands through research, policy, economic valuation, and adaptive management. An analysis of the land use changes due to agricultural expansion within the Golden Triangle, a representative agricultural area in the NGP, indicated that the proportion of land conversion to agriculture area was 84%, 8%, and 7% from grassland, riparian, and shrubland habitats, respectively. Our results showed this simplification was associated with a potential reduction of pollination services. Also, our economic analysis projected that if 30% parasitism could be achieved through better management systems, the estimated potential economic returns to pest regulation services through parasitoids in Montana, USA alone could reach about $11.23 million. Overall, while dryland agroecosystems showed a significant loss of native biodiversity and its services, greater pest incidence, and a decrease in plant pollinator networks, these trends were moderately reversed in organically managed farming systems. In conclusion, although land use changes due to agricultural expansion and industrialized farming threaten the sustainability of dryland agroecosystems, this impact can be partially offset by coupling ecologically-based farming practices with adaptive management strategies.