Negative effects of pesticides on wild bee communities can be buffered by landscape context

Abstract

Wild bee communities provide underappreciated but critical agricultural pollination services. Given predicted global shortages in pollination services, managing agroecosystems to support thriving wild bee communities is, therefore, central to ensuring sustainable food production. Benefits of natural (including semi-natural) habitat for wild bee abundance and diversity on farms are well documented. By contrast, few studies have examined toxicity of pesticides on wild bees, let alone effects of farm-level pesticide exposure on entire bee communities. Whether beneficial natural areas could mediate effects of harmful pesticides on wild bees is also unknown. Here, we assess the effect of conventional pesticide use on the wild bee community visiting apple (Malus domestica) within a gradient of percentage natural area in the landscape. Wild bee community abundance and species richness decreased linearly with increasing pesticide use in orchards one year after application; however, pesticide effects on wild bees were buffered by increasing proportion of natural habitat in the surrounding landscape. A significant contribution of fungicides to observed pesticide effects suggests deleterious properties of a class of pesticides that was, until recently, considered benign to bees. Our results demonstrate extended benefits of natural areas for wild pollinators and highlight the importance of considering the landscape context when weighing up the costs of pest management on crop pollination services.

Per-visit pollinator performance and regional importance of wild Bombus and Andrena (Melandrena) compared to the managed honey bee in New York apple orchards

“…We observed high spatial and temporal variation in wild bee abundance across orchards (Figure 1b). Bee abundance is positively tied to access to natural habitat and depressed with increasing intensity of pesticide regimes in orchards (Kennedy et al 2013;Martins et al 2015;Park et al 2015;Watson et al 2011). Therefore, growers have tools to increase wild bee abundance within their orchard, if desired.…”

“…Transitioning an orchard to rely more heavily on wild pollinators may require actions on the grower's part to increase and maintain wild bee abundance. Growers may optimize wild bee abundance by maximizing natural areas surrounding their orchards, decreasing pesticide intensity, and creating additional habitat and foraging resources for bees near orchards (Kennedy et al 2013;Park et al 2015;Watson et al 2011). This study continues to build on a growing body of evidence that wild bees benefit crop production and may buffer against declines in Apis populations.…”

“…Apple is visited by a diverse wild bee fauna in central New York (Gardner and Ascher 2006;Park et al 2015;Russo et al 2015). Recent work showing the positive influence of wild bee species richness and functional diversity on apple production and quality indicates that wild bee communities contribute significantly to apple pollination (Mallinger and Gratton 2015;Martins et al 2015).…”

“…To ensure commercial quality fruit and yields, New York apple growers commonly rent honey bees (Apis mellifera L., hereafter referred to as Apis ), with hive densities ranging from 0.4 to 2.8 hives per hectare in our study region, at US$65-85 per hive (Eve Consulting unpubl. data; Park et al 2015). However, colony losses due to BColony Collapse Disorder^in North America and competing pollination demands have fueled increased hive rental fees and supply shortages for apple growers (Oldroyd 2007;vanEngelsdorp et al 2009).…”

How should conservationists respond to pesticides as a driver of biodiversity loss in agroecosystems?

“…But the offsite impacts of agriculture, as evidenced by data on systemic pesticides, have now been 153 recognised as greater than often assumed, and the impacts of pesticides on non-target species 154 shown to be influenced by landscape context (Park et al, 2015). small-scale, labour-intensive, lower external-input farming systems, frequently leading to higher 184 yields than conventional systems (Pretty, 2008).…”