01
May
Study Finds Synergistic Convergence of Global Warming, Pesticide Toxicity, and Antibiotic Resistance
(Beyond Pesticides, May 1, 2025) Pesticides by themselves are a grave threat to global health. As is global warming. As is antibiotic resistance. Each of these problems has to be analyzed in its own silo to reveal the mechanisms driving its dynamics. But eventually it must be acknowledged that they actually converge. A common soil arthropod has clearly illustrated how this convergence creates synergistic effects: warming increases pesticide toxicity; pesticide toxicity triggers antibiotic resistance; antibiotic resistance spreads through horizontal gene transfer (movement through the environment to people) and predation. The consequences, not yet fully understood, are nevertheless emerging from accumulating research.
A study published in the Journal of Hazardous Materials by scientists at six Chinese universities and research centers examines the convergence in springtails (Folsomia candida), tiny insect-like animals that live in soils worldwide and are commonly used as laboratory subjects. They exposed springtails to the neonicotinoid insecticide imidacloprid at three concentrations and three temperatures. In addition to measuring the springtails’ direct mortality, the researchers also investigated the microbes in the animals’ guts, checking for expression of genes involved in antibiotic resistance.
The evidence is unequivocal: imidacloprid exposure at a soil temperature consistent with current and expected warming (30°C, or 86° Fahrenheit) killed significant numbers of springtails. Imidacloprid concentrations in the springtails were more than ten times higher at 30°C than at the two lower temperatures tested. Pesticide toxicity is known to increase with temperature, which affects how pesticides are metabolized, travel, and degrade in the environment. Higher temperatures also lower the threshold for pesticides’ lethality in soil invertebrates in part by forcing them to divert energy from reproduction and immunity to repair the heat damage.
When the researchers examined gene expression in the springtails’ gut microbes, they found similar evidence for the harmful combination of warming and pesticides. They detected 110 different antibiotic resistance genes (ARGs), and to dive deeper, they tested one microbe abundant in the springtails, Serratia liquefaciens, in further detail. The authors cite research showing that this bacterium also inhabits the domestic silk moth, the greater Indian fruit bat, and honey bees.
In the springtails, at 30°C and the highest imidacloprid concentration, ARGs increased significantly, particularly genes associated with stress survival and the ability of pathogenic microbes to enter and injure cells. The authors note that antimicrobial resistance is also enhanced through changes in microbial community structure, oxidative stress/reactive oxygen species production in host species, and increased permeability of cell walls.
Many of the ARGs the researchers found across bacterial species are deemed high-risk. For example, in the high-temperature, high-imidacloprid concentration groups, they detect a gene for tetracycline resistance, along with the gene dfrA, which confers resistance to trimethoprim (used for bladder and ear infections), and optrA, a gene that works against the antibiotic tedizolid, described elsewhere as “a last-resort antimicrobial agent in human medicine.” The antibiotic resistance genes in the springtails are found together with virulence factors, which intensify the pathogen’s damage to the host.
The current study shows that the increased presence of imidacloprid also increases the presence of imidacloprid-degrading bacteria, reducing the diversity of the microbiome. This in turn “diminishes the metabolic multifunctionality of soil microbial communities,” the authors write, which raises springtail mortality. They cite a 2019 study showing that this process can also trigger pesticide resistance in mosquitoes exposed to pyrethroid insecticides by increasing pyrethroid-degrading bacteria. While pesticides and antibiotics are not usually equated, the mechanism inducing resistance in both is essentially the same—clearly the pesticide-exposed springtails contain a wide variety of genes conferring resistance to antibiotics, adding to the growing body of research indicating that biological responses to pesticides affect responses to antibiotics, and vice versa.
A powerful factor in the risk landscape created by the convergence of these global threats is the potential for horizontal gene transfer throughout food webs. In the current study, the ARGs and virulence factors were also found with mobile genetic elements (MGEs), which comprise several types of genetic packages that can transfer these elements widely across species barriers.
In January, Beyond Pesticides analyzed a study by some of the same authors detailing this process in mites and springtails exposed to zinc thiazole, a fungicide and antibacterial chemical recently linked to thyroid disruption. The springtails’ gut microbes are incorporated into the mites’ gut microbiota, making resistance genes potentially available to new microbial taxa, and so on through the web.
In fact, the relationship between pesticides and antibiotics, and their mutual induction of various resistance processes in the biosphere, are serious problems that have received far too little regulatory and legislative attention. Glyphosate, 2,4-D and dicamba have all been documented to create resistance in Salmonella and E. coli.
Beyond Pesticides, along with the Natural Resources Defense Council, Migrant Clinicians Network, and several other advocacy groups sued the U.S Environmental Protection Agency (EPA) in 2021 over its approval of streptomycin for use in citrus farming. The practice does not work against the target pathogens, and fosters antibiotic resistance. Streptomycin is one of the few drugs useful against multidrug-resistant tuberculosis. In 2023 the Ninth Circuit Court of Appeals sided with the plaintiffs and the antibiotic is now banned as a pesticide; however, the court’s reasoning fails to grasp the science on antibiotic resistance that EPA ignores in its review, despite it being the biggest emerging threat to U.S. and global health. Overall, the antibiotic-resistance-inducing effects of pesticides have not been properly regulated. Beyond Pesticides has called for the immediate cancellation of “all uses of a pesticide when resistance is discovered or predicted to occur.”
The harmful effects on soil health of pesticides and antibiotics—with climate change as a third partner—cannot be overemphasized. Invertebrates cannot be deleted from soils without disastrous results. As Beyond Pesticides stated in 2021, “Healthy, living soils contain a universe of organisms, including many invertebrates, that provide critical services: they decompose biomass and cycle nutrients, maintain soil structure, hold carbon, and support ecosystem equilibrium by controlling pests and diseases, and making nutrients available to biota. Such organisms include earthworms, ground-nesting bees, beetles, ants, springtails, termites, millipedes, and others.”
Pesticide companies are shooting themselves in the foot. Their practices are unsustainable, and sooner or later the cumulative insults to the biosphere will overwhelm the ingenuity of companies to devise short-term “solutions” that merely hasten the day of their collapse. Switching to organic agriculture immediately is the wisest course. It can help disentangle a century or more of the synergies among pesticides, climate and antibiotic resistance.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Sources:
Warming exacerbates the effects of pesticides on the soil collembolan gutmicrobiome and antibiotic resistome
Ya-Ning Wang et al
Journal of Hazardous Materials 2025
https://www.sciencedirect.com/science/article/abs/pii/S0304389425012099
Dissemination of Antimicrobial Resistance in Microbial Ecosystems through Horizontal Gene Transfer
Christian J.H.vonWintersdorff et al
Frontiers in Microbiology
https://pmc.ncbi.nlm.nih.gov/articles/PMC4759269/
Meta-Review: Pesticides Kill or Harm Soil Invertebrates Essential to Soil Health
Beyond Pesticides, May 7, 2021
https://beyondpesticides.org/dailynewsblog/2021/05/meta-review-pesticides-kill-or-harm-soil-invertebrates-essential-to-soil-health/
Mechanism for Escalating Antibiotic Resistance in Agriculture Detailed in Study, as Crisis Grows
Beyond Pesticides, January 2, 2025
https://beyondpesticides.org/dailynewsblog/2025/01/mechanism-for-escalating-antibiotic-resistance-in-agriculture-detailed-in-study-as-crisis-grows/
Common Herbicides Linked to Antibiotic Resistance
Beyond Pesticides, March 30, 2015
https://beyondpesticides.org/dailynewsblog/2015/03/common-herbicides-linked-to-antibiotic-resistance/
