The current decline of invertebrates worldwide is alarming. Several potential causes have been proposed but heavy metals, while being a widespread and major pollutants of air, soils and water, have so far been largely overlooked. Here, we ran a meta-analysis of 527 datasets on the effects of arsenic, cadmium, lead and mercury on terrestrial invertebrates. These four well-studied metals, for which international guidelines exist, significantly impact the physiology and behavior of invertebrates, even at levels below those recommended as ‘safe’ for humans. Our results call for a revision of the regulatory thresholds to better protect terrestrial invertebrates, which appear to be more sensitive to metal pollution than vertebrates. More fundamental research is needed to improve international guidelines for metal pollutants, and to develop conservation plans to mitigate invertebrate declines and protect ecosystem services.

Pollutants can have severe detrimental effects on insects, even at sublethal doses. Agrochemicals have been identified as important causes of pollinator declines, but the impacts of other anthropogenic compounds, such as metallic trace elements contaminating soils and waters, have received considerably less attention. Here, we exposed honey bee colonies to chronic field-realistic concentrations of lead in food and demonstrate that consumption of this single trace element impaired bee cognition and morphological development. Honey bees exposed to the highest lead concentration had reduced olfactory learning performances and developed smaller heads, which may have constrained their cognitive functions. Our results show that lead pollutants can have dramatic effects on honey bee health and may contribute to the widespread decline of pollinators.