Anthropogenic air pollutants reduce insect-mediated pollination services

Common air pollutants, such as nitrogen oxides (NOx), emitted in diesel exhaust, and ozone (O-3), have been implicated in the decline of pollinating insects. Reductionist laboratory assays, focused upon interactions between a narrow range of flowering plant and pollinator species, in combination with atmospheric chemistry models, indicate that such pollutants can chemically alter floral odors, disrupting the cues that foraging insects use to find and pollinate flowers. However, odor environments in nature are highly complex and pollination services are commonly provided by suites of insect species, each exhibiting different sensitivities to different floral odors. Therefore, the potential impacts of pollution-induced foraging disruption on both insect ecology, and the pollination services that insects provide, are currently unknown. We conducted in-situ field studies to investigate whether such pollutants could reduce pollinator foraging and as a result the pollination ecosystem service that those insects provide. Using free-air fumigation, we show that elevating diesel exhaust and O-3, individually and in combination, to levels lower than is considered safe under current air quality standards, significantly reduced counts of locally-occurring wild and managed insect pollinators by 62-70% and their flower visits by 83-90%. These reductions were driven by changes in specific pollinator groups, including bees, flies, moths and butterflies, and coincided with significant reductions (14-31%) in three different metrics of pollination and yield of a self-fertile test plant. Quantifying such effects provides new insights into the impacts of human-induced air pollution on the natural ecosystem services upon which we depend.

Automated summary

Common air pollutants, such as nitrogen oxides and ozone, have been found to disrupt the foraging behavior of pollinating insects, leading to a decline in their population and reduced pollination services. In a field study, researchers demonstrated that elevated levels of diesel exhaust and ozone significantly reduced the counts of pollinators and their flower visits. These reductions were driven by changes in specific pollinator groups, and were associated with decreased pollination and yield of test plants.