Effects of Atmospheric Pollutants on Volatile-Mediated Insect Ecosystem Services

Primary and secondary atmospheric pollutants, including carbon monoxide (CO), carbon dioxide (CO₂), nitrogen oxides (NO_x), ozone (O₃), sulphur dioxide (SO₂) and particulate matter (PM_2.5/PM₁₀) with associated heavy metals (HMs) and micro- and nanoplastics (MPs/NPs), have the potential to influence and alter interspecific interactions involving insects that are responsible for providing essential ecosystem services (ESs). Given that insects rely on olfactory cues for vital processes such as locating mates, food sources and oviposition sites, volatile organic compounds (VOCs) are of paramount importance in interactions involving insects. While gaseous pollutants reduce the lifespan of individual compounds that act as olfactory cues, gaseous and particulate pollutants can alter their biosynthesis and emission and exert a direct effect on the olfactory system of insects. Consequently, air pollutants can affect ecosystem functioning and the services regulated by plant-insect interactions. This review examines the already identified and potential impacts of air pollutants on different aspects of VOC-mediated plant-insect interactions underlying a range of insect ES. Furthermore, we investigate the potential susceptibility of insects to future environmental changes and the adaptive mechanisms they may employ to efficiently detect odours. The current body of knowledge on the effects of air pollutants on key interspecific interactions is biased towards and limited to a few pollinators, herbivores and parasitoids on model plants. There is a notable absence of research on decomposers and seed dispersers. With exception of O₃ and NO_x, the effects of some widespread and emerging environmental pollutants, such as secondary organic aerosols (SOAs), SO₂, HMs, PM and MPs/NPs, remain largely unexplored. It is recommended that the identified knowledge gaps be addressed in future research, with the aim of designing effective mitigation strategies for the adverse effects in question and developing robust conservation frameworks.