Crop pollination by native honey bees (Apis cerana) at risk due to agricultural intensification: Impact of farming systems

1. Agricultural intensification in Lao PDR has increased significantly each year, resulting in the conversion of vast natural habitats to various levels of agricultural intensification. However, there has been a longstanding knowledge gap regarding the impact of agricultural intensification on native fauna species in the country, which has been overlooked for centuries.2. The present study was conducted in two different agricultural systems (organic and conventional), which varied in land-use intensity, in central Lao PDR. Within each farming system, five sampling plots (30 x 50 m), spaced 100 m apart, and 900 m distance between organic and conventional farming systems were selected. In both farming systems, a diverse range of vegetables, crops and fruit orchards, comprising more than 50 flowering plant species throughout the year, was cultivated across a mean plot size of ≥ 15 ha.3. The farming system had the greatest influence on native honey bee abundance. Although honey bee abundance was higher in the organic, the diversity of flowering plant resources did not differ significantly between the two farming systems. Honey bee abundance was consistently related to the farming system throughout the study period, whereas the diversity of flowering plant resources was not. This suggests that the farming system has a more crucial impact on native honey bee populations than on the diversity of flowering plants.4. In organic farming, it was found that native honey bee populations could provide full pollination services, even for crops with high pollination demands (e.g., melon), both inside and outside greenhouses, without the need for other pollinators.5. All other sampling plots in the conventional farming system, however, showed a significant decline in native bee abundance, resulting in insufficient pollination services from native bees alone. This study found that diversity is crucial for sustaining these services, given the year-to-year variation in population levels. While organic farming can help sustain pollination services provided by generalist native honey bees in agricultural landscapes, additional measures are needed to conserve more specialized native honey bee species and other pollinators in both farming systems.