In the battle against air pollution, it’s not just humans who suffer. Beneficial invertebrates, crucial for pollination, pest control, and nutrient cycling, are being disproportionately harmed by common air pollutants. This meta-analysis has unveiled the extent of this hidden crisis, highlighting the urgent need for action.
Air Pollution: A Global Issue
The idea for this paper stemmed from a field study that we undertook at the University of Reading using a pilot Free-Air Diesel and Ozone Enrichment (FADOE) facility, which demonstrated severe detrimental effects of air pollution on pollinator visitation to flowers1. We therefore decided to conduct a meta-analysis to understand whether the harmful effects we were seeing in the field were widespread.
This study analyzed data from 120 publications across 19 countries, revealing that air pollutants, including ground-level ozone (O3), nitrogen oxides (NOx), sulfur dioxide (SO2) and particulate matter (PM), significantly impair the performance of beneficial invertebrates while leaving harmful pests largely unaffected. The pest status of invertebrates was categorised into significant economic pests (based on their presence within two major plant pest databases), other herbivores (i.e. those not described in the plant pest databases), and beneficial invertebrates.
Beneficial Invertebrates: The Silent Sufferers
Beneficial invertebrates, including pollinators like bees and butterflies, natural pest regulators such as ladybirds and parasitic wasps, and detritivores that break down organic matter, are essential for maintaining healthy ecosystems. These creatures support food production, control pest populations, and contribute to soil health. However, the study found that air pollution reduces their performance by a third, a stark contrast to the negligible impact on pest species.
Ozone: The Chief Culprit
Among the pollutants, tropospheric ozone emerged as the most detrimental to beneficial invertebrates. Even at field-realistic levels below current air quality standards, ozone significantly impaired their performance. This finding is particularly alarming given that ozone levels have more than doubled since pre-industrial times and are projected to rise further2, 3.
How Pollutants Affect Invertebrates
Air pollutants affect invertebrates in various ways. Physiologically, they can induce harmful changes at the molecular level, affecting growth, reproduction, and survival. Indirectly, pollutants alter the nutritional quality of plants and disrupt the chemical signals that many invertebrates rely on for navigation and communication. For example, pollutants can degrade volatile organic compounds (VOCs) that plants emit to attract pollinators or signal distress4, 5.
The Bigger Picture
The findings of this study underscore the need for stricter air quality regulations and effective mitigation strategies to protect our plant’s invaluable natural services. While efforts to reduce emissions from vehicles and industrial sources are ongoing, this study suggests that even low levels of pollution can have far-reaching impacts on invertebrate populations. The decline of beneficial invertebrates is a part of a broader trend of biodiversity loss driven by human activities. Land use changes, climate change, and the introduction of invasive species compound the pressures on invertebrate populations6. This meta-analysis provides a crucial piece of the puzzle, highlighting air pollution as a significant but often overlooked factor.
Further field studies, using the University of Reading’s new FADOE platform7, are underway to determine the mechanisms associated with air pollution-mediated changes in invertebrate populations and identify strategies that we can use to mitigate the deleterious effects of air pollution on our valuable ecosystem services.
References
Ryalls JMW, et al. Anthropogenic air pollutants reduce insect-mediated pollination services. Environmental Pollution 297, 118847 (2022).
Chen Z-Y, Petetin H, Méndez Turrubiates RF, Achebak H, Pérez García-Pando C, Ballester J. Population exposure to multiple air pollutants and its compound episodes in Europe. Nature Communications 15, 2094 (2024).
IPCC. Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press (2013).
Blande JD. Effects of air pollution on plant–insect interactions mediated by olfactory and visual cues. Current Opinion in Environmental Science & Health 19, 100228 (2021).
Knaden M, et al. Human impacts on insect chemical communication in the anthropocene. Frontiers in Ecology and Evolution 10, 791345 (2022).
IPBES. Summary for policymakers of the global assessment report on biodiversity and ecosystem services of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. (ed S. Díaz JS, E. S. Brondízio E.S., H. T. Ngo, M. Guèze, J. Agard, A. Arneth, P. Balvanera, K. A. Brauman, S. H. M. Butchart, K. M. A. Chan, L. A. Garibaldi, K. Ichii, J. Liu, S. M. Subramanian, G. F. Midgley, P. Miloslavich, Z. Molnár, D. Obura, A. Pfaff, S. Polasky, A. Purvis, J. Razzaque, B. Reyers, R. Roy Chowdhury, Y. J. Shin, I. J. Visseren-Hamakers, K. J. Willis, and C. N. Zayas). IPBES secretariat (2019).
Mofikoya AO, James L, Mullinger NJ, Ryalls JMW, Girling RD. A novel Free-Air Diesel and Ozone Enrichment (FADOE) research platform. Methods X 12, 102635 (2024).