Creating patches of native flowers facilitates crop pollination in large agricultural fields: mango as a case study

Abstract

Summary1. As cropland increases, fields become progressively isolated from pollinators, leading to declines in pollinator-dependent crop productivity. With the rise in demand for pollinatordependent foods, such productivity losses may accelerate conversion of natural areas to cropland. Pollination-compensation measures involving managed pollinators or hand pollination are not always optimal or are too costly. Introducing areas of native vegetation within cropland has been proposed as a way to supplement crop pollinators, but this measure is perceived by farmers to carry costs outweighing benefits to agricultural production. Studies quantifying benefits of small patches of native flowers to crop pollination are therefore necessary to encourage such practices. 2. To ascertain whether provision of floral resources within farmlands can facilitate pollination, and hence, crop yields, small experimental patches of perennial native plants (native flower compensation areas, NFCAs) were created in nonproductive areas of large commercial fields of several cultivars of mango Mangifera indica. 3. Pesticide use and isolation from natural habitat were associated with declines in flying visitors and in mango production (kg of marketable fresh fruit), but presence of NFCAs ameliorated these declines, and NFCAs did not harbour any mango pests. In areas far from natural vegetation, orchards near NFCAs had significantly higher diversity and abundance of mango flying visitors, as well as mango production, than orchards far from NFCAs, although these measures were still lower than in orchards close to natural areas. 4. Neither the most abundant flower visitors to mango (ants) nor initial fruit set was significantly affected by distance, pesticides or NFCAs, suggesting that although fertilization is associated with factors unaffected by isolation from natural habitat and pesticide use (i.e. selfand ant-pollination), viable fruit set (and ultimately, production) requires cross-pollination, for which flying visitors are essential. 5. Synthesis and applications. Our results show that the presence of small patches of native flowers within large farms can increase pollinator-dependent crop production if combined with preservation of remaining fragments of natural habitat and judicious use of pesticides. Native flower compensation areas represent a profitable management measure for farmers, increasing cost-effectiveness of cropland while indirectly contributing to preservation of natural habitat.

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

“…Evidence is building for the susceptibility of wild bee communities to pesticides in agricultural fields and landscapes [18,55,59,70,72]. Our findings suggest that heavy use of conventional pesticides, even some traditionally viewed as benign [39], can render our crops net sinks for bee populations.…”

Massively Introduced Managed Species and Their Consequences for Plant–Pollinator Interactions

“…A few studies have considered the consequences of distance from natural habitats on within-crop plant-pollinator networks (Carvalheiro et al, 2010(Carvalheiro et al, , 2012). These studies demonstrate that the diversity of pollinators on crops declines with increasing distance to natural habitats, both in mango plantations (Carvalheiro et al, 2010) and in sunflower fields (Carvalheiro et al, 2012, see also Ricketts et al, 2008. When distance to natural habitats increases, the decrease in pollinator diversity also leads to a reduction of network complexity up to the single couple MFCmanaged honeybees (see Box 3).…”

Indirect interactions between crops and natural vegetation through flower visitors: the importance of temporal as well as spatial spillover

“…Previous studies have found that natural vegetation in the area is a source of both flower visitors (Carvalheiro et al, 2010(Carvalheiro et al, , 2012Geslin et al, 2016) and natural enemies of crop pests (Henri et al, 2015;Morgan et al, 2017) in mango fields. Mangos in turn have been shown to harbour pests that can spill over into natural vegetation (Moxley et al, 2017), and it is likely that pollinators, too, spill over into natural vegetation.…”