Bees’ pesticide risk is species and landscape-dependent

Posted on: 02 March 2023

According to the ecologists, increased agricultural land surrounding bees increases pesticide-related risk, but only for the solitary bee and bumble bee – species that forage over smaller areas than the honey bee. 

In broad terms, these findings support the capacity of semi-natural areas to reduce pesticide risk for wild bees.

Jessica Knapp, Assistant Professor of Ecology at Trinity College Dublin, previously at Lund University, said:

“Agricultural landscapes expose bees to pesticides as their activity coincides with pesticide use, but different species each have different ecological traits – like foraging range, for example – which together determine this activity. As a result, different species likely face different pesticide exposure and risk.”

Pesticide risk assessment is evolving to capture this ecological complexity but requires a greater understanding. This newly published study evidences this at a landscape scale as the ecologists measured pesticide concentrations in different food sources for different bee species in multiple cropping systems.

A researcher carefully collects a pollen sample from a bee. Image: Daphne Wong.

Dr Knapp added:

“In contrast to previous work, we combined multiple aspects of pesticide exposure usually restricted to individual studies, such as landscape contexts, pollinator species, crop types and food sources.”

“Most pesticide-related risks came from a few insecticides. The study thus points to specific pesticide uses that could be changed to reduce pesticide-related risks for bees. Furthermore, pesticide risk correlated between nectar and pollen and among bee species but was highest in honey bee-collected pollen. These results are practically relevant because they suggest that, to some extent, we can cautiously predict risk among bee species and food sources.

These results are timely as the European Commission has just revised the EU Pollinator Initiative, taking stronger and broader action to reverse the decline of pollinators, including bees, by 2030. These actions align with the Commission's Farm to Fork Strategy, which aims to decrease pesticide use and environmental risk by 50 percent by 2030. 

Maj Rundlöf, a biology researcher at Lund University, added:

“To track the success of this target in reducing pesticide risk, we need studies like ours that provide information on how current agricultural practices and approved pesticide use lead to exposure levels and frequencies of, often multiple, pesticides for non-target organisms such as bees. 

“Based on our results, we suggest that honey bee-collected pollen could form the basis for tracking bees’ pesticide-related risk in agricultural landscapes.”

The study has just been published in the leading journal, Nature Ecology and Evolution and can be read on the publisher's website.

This work is part of the MixToxBee project led by Lund University.

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