Creating patches of native flowers facilitates crop pollination in large agricultural fields: mango as a case study.
Abstract
As cropland increases, fields become progressively isolated from pollinators, leading to declines in pollinator-dependent crop productivity. With the rise in demand for pollinator-dependent 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. 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. 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. 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. self- and ant-pollination), viable fruit set (and ultimately, production) requires cross-pollination, for which flying visitors are essential. 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.