Crop diversity and semi-natural habitat a boon to yields as well as pollinators

Agricultural areas today are frequently made up of large fields with simple crop rotations consisting of only a very few species and low levels of natural habitats. This low level of biodiversity has seen a decline in the insects, especially bees, that play a key role in pollination for those crops. The foraging activities of bees are limited by their flight range from the central point of their nests, making the preservation of wooded areas and grasslands, termed semi-natural habitats (SNH), important to supporting their services in agriculture.

In a recent article published in Agriculture, Ecosystems and Environment, lead author Chloé A. Raderschall and colleagues set out to determine whether an increase in landscape crop diversity will support a higher pollinator density by providing a wider variety and more continuous source of resources for them. They also looked at the effect of different proportions of SNH in the vicinity of agricultural fields. The authors studied 14 different faba bean fields in southern Sweden that sit along gradients of landscape crop diversity and proportion of SNH, surveying the pollinators and their activities.

Results indicated that higher landscape crop diversity did indeed increase bumble bee densities. A higher proportion of SNH also resulted in higher densities of both bumble bees and honey bees, as well as higher bean yields. Pollinator densities, however, were not the main cause of the higher yields found in the presence of more SNH, though in general, greater pollinators result in better yields in faba beans. The authors speculate that the higher yield may have been related to differing pest pressures associated with having more SNH in the surrounding landscape, though they did not test this.

“From an agricultural perspective, increasing SNH in the landscape also increases yield in faba beans. Thus, the retention of SNH benefits both pollinator conservation and crop production,” write the authors. “We recommend that future agri-environmental schemes and agricultural policies strongly support an increase in crop diversity in agricultural landscapes, by incentivising the lengthening of crop rotations for example, while the conservation of existing SNH should be maintained.”