Effects of livestock-dominated landscapes and pesticides on bees and pollination services in the Andes

Land-use change and pesticides have been identified as two of the main causes behind bee decline. Understanding how these factors affect pollinator communities is crucial to inform practices that generate optimal pollination and ensure sustainable food production. A case in point is the Andean ecosystems, which are experiencing a rapid transformation of natural habitat into grazing areas for cattle ranching. Pastures are now covering 65.2% of the Andes and are the biggest driver of forest loss. There is also a tendency in the region to increase pesticide use without robust regulations. Nonetheless, there is little information on how these processes are impacting bees and pollination services. In a series of experiments, we studied how land-use gradients and pesticide use in fruit production and cattle ranching farms affect bees and ecosystem services. We demonstrated that increased pasture area and insecticide residues in flowers reduce bee richness, and consequently yield in a fruit crop. We also discovered that increased pasture in the landscape is associated with the presence of veterinary insecticides in stingless bee colonies. We collected evidence showing that those pesticide residues are coming from flowers contaminated with manure from pesticide-treated cattle. Interestingly, farms with high proportions of natural habitat ( >33%) demonstrated to partially mitigate negative pesticide effects on bee richness. Overall, these results suggest that the expansion of pastures for cattle ranching, and the use of pesticides are reducing bee diversity and productivity in local crops.