Bee pollination outperforms pesticides for oilseed crop production and profitability

Abstract

Nature-based agriculture that reduces dependency on chemical inputs requires using ecological principles for sustainable agro-ecosystems, aiming to balance ecology, economics and social justice. There is growing evidence that pollinator-dependent crops with high insect, particularly bee, pollination service can give higher yields. However, the interacting effects between insect pollination and agricultural inputs on crop yields and farm economics remain to be established to reconcile food production with biodiversity conservation. We quantified individual and combined effects of pesticides, insect pollination and soil quality on oilseed rape (Brassica napus L.) yield and gross margin, using a total of 294 farmers' fields surveyed between 2013 and 2016. We show that yield and gross margins are greater (15-40%) in fields with higher pollinator abundance than in fields with reduced pollinator abundance. This effect is, however, strongly reduced by pesticide use. Greater yields may be achieved by either increasing agrochemicals or increasing bee abundance, but crop economic returns were only increased by the latter, because pesticides did not increase yields while their costs reduced gross margins.

Keywords: agroecology; herbicide; insecticide; nature-based solutions; pollinators; rapeseed.

Figure 1.

Schematic relationships between soil type, agricultural practices, bees, landscapes and their effect on yield and economic returns. Red arrows indicate negative interactions, whereas green ones show positive ones.

Figure 2.

Relationship between insecticides, herbicides on yield (a,b) and gross margins (c,d), n = 294. Solid lines show significant regressions and dashed lines non-significant regressions. Values for both herbicides and insecticides were centred/reduced.

Figure 3.

(a) The effect of pest (blue dots) and bee (green dots) abundance on gross margins; (b) the effect on yield; (c) the effect of insecticides on bees and pests; and (d) the relationship between pest and bee abundances. Abundances were centred/reduced. Solid lines show significant regressions and dashed lines non-significant regressions. Bee abundance includes honeybee plus Lasioglossum spp.

Figure 4.

Effect of interaction between bee abundance and the combined herbicide and insecticide TFI on yield (a) and gross margins (b). The green surface shows regions where the yield or gross margin is higher and blue where it is lower. Coloured points represent the raw data points and the black ones predicted values from the model. Positive and negative differences between raw data and predicted values are indicated in blue and green. Bee abundance includes honeybee and Lasioglossum spp., and pesticide TFI is the sum of insecticide and herbicide TFIs. Both explanatory variables were centred/reduced before analysis.