Biodiversity boosts crop pollinators and pest controllers, study finds

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  • A new study looks at the reliance on biodiversity of ecosystem services provided by pollinating and pest-controlling insects.
  • Up to half of the detrimental impacts of the “landscape simplification” that monocropping entails come as a result of a diminished mix of ecosystem service-providing insects.
  • The scientists found that the reduction in ecosystem services provided by these insects tended to lead to lower crop yields.

Farms with just one or a handful of different crops encourage fewer species of pollinating and pest-controlling insects to linger, ultimately winnowing away crop yields, according to a new study.

Up to half of the detrimental impacts of the “landscape simplification” that monocropping entails come as a result of a diminished mix of ecosystem service-providing insects, a team of scientists reported Oct. 16 in the journal Science Advances.

“Our study shows that biodiversity is essential to ensure the provision of ecosystem services and to maintain a high and stable agricultural production,” Matteo Dainese, the study’s lead author and a biologist at Eurac Research in Bolzano, Italy, said in a statement.

A hoverfly pollinating an oilseed rape flower. Image by Matthias Tschumi/Agroscope.
A hoverfly pollinating a rapeseed flower. Image by Matthias Tschumi/Agroscope.

It stands to reason that, with declines in the sheer numbers of insects that ferry pollen from plant to plant and keep crop-eating pests under control, these services will wane as well. But until now, it hasn’t been clear how monocultures affect the number and mix of these species or how crop yields might change as a result.

Aiming to solve these questions, Dainese and his colleagues pulled together data from 89 studies cutting across a variety of landscapes, from the tropics of Asia and Africa to the higher latitudes of northern Europe. They tabulated the number of pollinating and pest-controlling insects at these sites — both the absolute number of individuals and the number of species — along with an assessment of the ecosystem services the insects provided.

Extensive landscape where crops alternate with hedges, flowering strips and other seminatural habitats. Image by Matthias Tschumi/Agroscope.
Extensive landscape where crops alternate with hedges, flowering strips and other seminatural habitats. Image by Matthias Tschumi/Agroscope.

In almost all of the studies they looked at, the team found that a more diverse pool of these species translated into more pollination and greater pest control. They also showed that simplified landscapes supported fewer species of service-providing insects, which ultimately led to lower crop yields.

The researchers also looked at a third measure of the makeup of insect populations — what they called “evenness.” In natural ecosystems, a handful of dominant species with many more individuals typically live alongside a higher number of rarer species. The team found as landscapes became less diverse, dominant species numbers dwindled and rare species gained ground. This resulting, more equitable mix led to less pollination (though it didn’t end up affecting pest control).

A lacewing larvae predating on aphids on potato plant. Image by Matthias Tschumi/Agroscope.
A lacewing larvae predating on aphids on a potato plant. Image by Matthias Tschumi/Agroscope.

“Our study provides strong empirical support for the potential benefits of new pathways to sustainable agriculture that aim to reconcile the protection of biodiversity and the production of food for increasing human populations,” Ingolf Steffan-Dewenter, one of the study’s authors and an animal ecologist at the University of Würzburg in Germany, said in the statement.

The scientists figure that the richness of pollinator species explains around a third of the harmful impacts of less diverse landscapes, while the richness of pest-controlling species accounts for about half of the same measure. In their view, the results of their research point to the need to protect biodiversity on and around crops in an uncertain future.

“Under future conditions with ongoing global change and more frequent extreme climate events, the value of farmland biodiversity ensuring resilience against environmental disturbances will become even more important,” Steffan-Dewenter said.

Pictured is an Argynnis paphia female on vegetation. Image by Julia M Schmack/University of Auckland.
Pictured is an Argynnis paphia female on vegetation. Image by Julia M. Schmack/University of Auckland.

Banner image of a ladybird predating on aphids on potato plant by Matthias Tschumi/Agroscope. 

John Cannon is a staff writer at Mongabay. Find him on Twitter: @johnccannon

Citation:

Dainese, M., Martin, E. A., Aizen, M. A., Albrecht, M., Bartomeus, I., Bommarco, R., … Steffan-Dewenter, I. (2019). A global synthesis reveals biodiversity-mediated benefits for crop production. Science Advances, 5(10), eaax0121. doi:10.1126/sciadv.aax0121

Article Source: Mongabay