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Soil Biota

Impact of Pesticides on Soil Biota

Soil biota can be affected directly or indirectly, through pesticide use and conventional farming technologies that promote the use of pesticides.                                               

  • A study by LeBlanc et. al. in 2007 found that the rhizospheres (soil and microorganisms around the roots of a plant or tree) of Bacillus thuringiensis (Bt)-modified trees meant to alleviate insect damage had clear alterations when compared to the rhizospheres of non-Bt modified trees.
  • In 2013, a study by Anjum et. al. found that silver nanoparticles, a novel nanomaterial that the EPA recently agreed to regulate, has  a profound effect on soil microorganisms, leading to a collapse in metabolic abilities and diversity in soils with low organic matter. Similar effects were found in soil with high organic matter, but to a lesser extent.
  • Earthworms are excellent indicators of soil health, and provide vitally important ecosystem services by aerating the soil, cycling nutrients, and increasing microbial activity:
        • Earthworms
          In 2014, researchers also found that earthworms exposed to fungicides in conventionally farmed soil were at a stark disadvantage to worms in land managed organically. Earthworms exposed to the fungicide epoxiconazole were able to detoxify the chemical, but gained half as much weight as worms from an organic farm, where their population was also 2 to 3 times higher.
        • A 2013 study compared the health and growth of earthworms in soil containing carbon and silver nanoparticles at varying amounts with worms in regular soil. Researchers found the soil containing nanoparticles reduced reproduction, slowed growth, and increased the mortality rate of exposed earthworms. Although nanoparticles are increasingly added to a wide range of consumer products, very little is known about the potential risks these materials pose to the health of our environment. 
        • Another study on worms demonstrated the detrimental effects that pesticides can have on soil biota, finding that chronic and/or acute exposure to glyphosate and/or mancozeb promotes neurodegeneration in GABAergic and DAergic neurons in Caenorhabditis elegans, a type of roundworm.
  • Mycorrhizae fungi within soil are relied on by most plants for nutrients and moisture:
        • One study reported that exposure to pesticides inhibited mycorrhizae colonization and found that the accumulation of nitrogen, phosphorus, and potassium (NPK), necessary elements for plant health, was lower in pesticide-treated plants compared to control plants.
        • Another study found that spore germination and cell growth of mycorrhizae, Glomus mosseae, was adversely affected by pesticides used in agriculture, and in some cases, at much lower concentrations than are approved for use. 

[See More Scientific Studies Below]

Economic Cost

The microbes in soil are essential to ecosystem functioning because they break down organic matter and enable chemical elements to be reused. They are also nitrogen fixers, which is necessary for plants and the ecosystem as a whole. Earthworms are an intrinsic part of soil biota, providing support for important ecosystem functioning. Their burrows, sometimes deep into the soil, create pores for moisture and oxygen to travel and their waste becomes part of soil structure. They also break down dead organic matter and incorporate new organic matter into soil systems.

When pesticides reduce species diversity within the soil, it impacts the ecosystem as a whole. The European Academies' Science Advisory Council (EASAC) estimates soil organisms and their role in agricultural productivity to be worth $25 billion a year, globally.

Litigation & Lawsuits

In early 2015, EPA finally agreed to regulate novel nanomaterial pesticides as a result of a lawsuit filed by Center for Food Safety (CFS) and joined by Beyond Pesticides in December. In 2008, a coalition of more than 13 organizations filed a legal petition requesting, among other things, that EPA recognize the risks associated with a growing class of nano-silver consumer products and regulate them as new pesticides. After EPA had failed to respond to the petition for six years, in December 2014 some of the petitioner groups sued the agency to force it to respond. That lawsuit succeeded in March 2015, with EPA issuing a response.

Quick Links

What Can You Do?

  • Learn about the Hazards and Alternatives to using lawn pesticides.
  • Go Organic – Visit our Eating with a Conscience page to learn why eating organic foods is the right choice.
  • Visit our Tools for Change page to learn how to organize your community against pesticide use.
  • Sign up for Beyond Pesticides’ Action Alerts to stay up-to-date on the latest petitions and news. 
  • Scientific Studies: 

    • Effect of Mineral Fertilizers and Pesticides Application on Bacterial Community and Antibiotic-Resistance Genes Distribution in Agricultural Soils
      Soils are a hotspot for the emergence and spread of antibiotic resistance. The effects of agrochemical treatments on the bacterial community of agricultural soils and the content of antibiotic-resistance genes (ARGs) were studied. Treatments included the following: control, mineral fertilizers (NPKs), pesticides, and the combined treatment of soils under soya (Glycine max), sunflower (Helianthus annuus L.), and wheat (Triticum aestivum). Bacterial community taxonomic composition was studied using 16S rRNA gene sequencing. The content of 10 ARGs and 3 integron genes (intI1, intI2, intI3) was determined using quantitative real-time PCR. The results showed that the treatments had little effect on the taxonomic composition and diversity of the soil bacterial community. The most significant factors determining differences in the microbial community were sampling time and soil physico-chemical parameters. A significant role of the bacterial community in ARG distribution in soils was demonstrated. Representatives of the Pseudomonas, Bacillus, Sphingomonas, Arthrobacter genera, and the Nocardioidaceae and Micrococcaceae families were likely ARG hosts. The presence of integron genes of all three classes was detected, the most numerous being intI3. This work provides important information on the role of agricultural soils in ARG transfer, and the findings may be useful for sustainable and safe agricultural development.
      [Khmelevtsova, L. et al. (2024) Effect of mineral fertilizers and pesticides application on bacterial community and antibiotic-resistance genes distribution in agricultural soils, Agronomy. Available at: https://www.mdpi.com/2073-4395/14/5/1021]
    • Effects of sustainable agricultural practices on soil microbial diversity, composition, and functions
      Soil microorganisms can provide multiple benefits to agroecosystems, which are assumed to be promoted by sustainable agricultural practices. However, the mechanisms that explain this relationship have not been clearly elucidated. Although studies have reported that sustainable agricultural practices promote microbial biomass, the broader implications for soil microbial composition and functions remain uncertain. Accordingly, we searched field experiments worldwide contrasting soil microbial communities under conventional and sustainable agricultural practices. We analysed 924 results of relative abundance of bacteria or fungi (using 16 S and ITS rRNA amplicon sequencing, respectively) at the Family taxonomic level obtained from 46 articles. We found higher soil bacterial richness and higher abundance of copiotrophic bacteria under sustainable agricultural practices. Organic fertilisation promoted the abundance of bacteria involved in C and N cycling, while conservation tillage decreased those involved in the decomposition of plant residue. While sustainable agricultural practices had a minor effect on the overall fungal structure, they led to increases in symbiotic fungi abundance (e.g., Geoglossaceae). Additionally, we observed a slight increase in arbuscular mycorrhizal fungi and a slight reduction in pathogenic fungi associated with plant disease (e.g., Botryosphaeriaceae). Higher soil microbial taxonomic diversity did not lead to increased soil multifunctionality; however, it could safeguard resilience for soil functions via the diversity insurance effect. This study establishes that sustainable agricultural practices can significantly influence microbial communities, leading to compositional and structural changes, as well as promoting relevant functions for agroecosystems. Altogether, these results highlight the importance of integrating concepts of community ecology into agricultural management practices for reaching sustainable agricultural systems.
      [Mondaca, P. et al. (2024) ‘Effects of sustainable agricultural practices on soil microbial diversity, composition, and functions’, Agriculture, Ecosystems & Environment, 370, p. 109053. doi:10.1016/j.agee.2024.109053.]
    • Herbicides and pesticides synergistically interact at low concentrations in complex mixtures
      Assessing a complex mixture of pesticides at the impacted sites has been challenging for risk assessors for 50 years. The default assumption is that at low concentrations, pesticides interact additively with one another; thus, the risk posed by each component of a complex mixture could be simply added up. The EPA interaction-based hazard index (HIInteraction) modifies this assumption using a binary weight-of-evidence (BINWOE). However, data gaps often preclude HIInteraction use at most sites. This study evaluated these assumptions using the BINWOE to estimate the hazard index (HI) of select pesticide mixtures. The lack of in vivo binary interaction data led us to use a cell line, SH-SY5Y, to obtain the data necessary for the BINWOE approach. In the risk assessment, we considered the most active exposure scenario inhaling a mixture of volatile pesticides from contaminated soil and groundwater. The potential interactions between pesticides in 15 binary mixtures were investigated using the MTT assay in SH-SY5Y cells. Our findings showed that 60% of the binary mixtures elicited synergism (in at least one concentration), 27% displayed antagonism, and 13% showed additive effects in SH-SY5Y cells. Combining human safety data with in vitro interaction data indicated that adults and toddlers were at the highest risk when considering industrial and commercial land use, respectively, compared to other subpopulations. Incorporating interaction data into the risk assessment either increased the risk by up to 20% or decreased the risk by 2%, depending on the mixture. Our results demonstrate the predominant synergistic interactions, even at low concentrations, altered risk characterization at the complex operating site. Most concerning, organochlorine pesticides with the same mechanism of action did not follow dose additivity when evaluated by SH-SY5Y cell lines. Based on our observations, we caution that current HI methods based on additivity assumptions may underestimate the risk of organochlorine mixtures.
      [Alehashem, M. et al. (2024) Herbicides and pesticides synergistically interact at low concentrations in complex mixtures, Chemosphere. Available at: https://www.sciencedirect.com/science/article/pii/S0045653524003242?via%3Dihub. ]
    • Modeling pesticides and ecotoxicological risk assessment in an intermittent river using SWAT
      The present work aimed to predict the fate of two pesticides, copper (Cu) and glyphosate in a Mediterranean basin with an intermittent river and to assess the ecotoxicological risk related to their presence in water bodies coupling field measurements of streamflow and pesticide concentrations, and an eco-hydrological model. The Soil and Water Assessment Tool (SWAT) model was calibrated and, subsequently used to assess predicted environmental concentrations of pesticides in surface waters. The ecotoxicological risk related to the presence of Cu and glyphosate in surface water was assessed at the reach scale by using the Toxicity to Exposure Ratio approach (TER). Measurements of glyphosate concentrations (< 0.5 μg l−1) exceeded the maximum European threshold of environmental quality standards for pesticides (EQS) of 0.1 μg l−1. High concentrations of glyphosate were predicted in the wet season and in September, when glyphosate is mostly used in vineyards and olive grove productions. Acute risk (TER < 100) associated with the presence of glyphosate was detected for several reaches. High concentrations of Cu (< 6.5 μg l−1), mainly used as a fungicide in vineyards, were predicted in several river reaches. The results of the ecotoxicological risk assessment revealed that November and January were the critical months during which most of the river reaches showed a chronic risk associated with the presence of Cu.
      [Centanni, M. et al. (2024) Modeling pesticides and ecotoxicological risk assessment in an intermittent river using Swat, Scientific Reports. Available at: https://www.nature.com/articles/s41598-024-56991-6#Sec14. ]
    • Organic farming promotes the abundance of fungi keystone taxa in bacteria-fungi interkingdom networks
      Soil bacteria-fungi interactions are essential in the biogeochemical cycles of several nutrients, making these microbes major players in agroecosystems. While the impact of the farming system on microbial community composition has been extensively reported in the literature, whether sustainable farming approaches can promote associations between bacteria and fungi is still unclear. To study this, we employed 16S, ITS, and 18S DNA sequencing to uncover how microbial interactions were affected by conventional and organic farming systems on maize crops. The Bray–Curtis index revealed that bacterial, fungal, and arbuscular mycorrhizal fungi communities were significantly different between the two farming systems. Several taxa known to thrive in healthy soils, such as Nitrosophaerales, Orbiliales, and Glomus were more abundant in the organic farming system. Constrained ordination revealed that the organic farming system microbial community was significantly correlated with the β-glucosidase activity, whereas the conventional farming system microbial community significantly correlated with soil pH. Both conventional and organic co-occurrence interkingdom networks exhibited a parallel node count, however, the former had a higher number of edges, thus being denser than the latter. Despite the similar amount of fungal nodes in the co-occurrence networks, the organic farming system co-occurrence network exhibited more than 3-fold the proportion of fungal taxa as keystone nodes than the conventional co-occurrence network. The genera Bionectria, Cercophora, Geastrum, Penicillium, Preussia, Metarhizium, Myceliophthora, and Rhizophlyctis were among the fungal keystone nodes of the organic farming system network. Altogether, our results uncover that beyond differences in microbial community composition between the two farming systems, fungal keystone nodes are far more relevant in the organic farming system, thus suggesting that bacteria-fungi interactions are more frequent in organic farming systems, promoting a more functional microbial community.
      [Matteoli, F.P. et al. (2024) ‘Organic farming promotes the abundance of fungi keystone taxa in bacteria-fungi interkingdom networks’, World Journal of Microbiology and Biotechnology, 40(4). doi:10.1007/s11274-024-03926-y.]
    • Organic food has lower environmental impacts per area unit and similar climate impacts per mass unit compared to conventional
      In recent years, interest in studying the climate and environmental impact of organic food has grown. Here, we compared the environmental impacts of organic and conventional food using data from 100 life cycle assessment studies. Most studies focused on climate impacts, with fewer addressing biodiversity loss and ecotoxicity. Findings revealed no significant differences in global warming, eutrophication potential, and energy use per mass unit. However, organic food showed lower global warming, eutrophication potential, and energy use per area unit, with higher land use. Additionally, organic farming showed lower potential for biodiversity loss and ecotoxicity. Challenges in life cycle assessment include evaluating biodiversity, toxicity, soil quality, and carbon changes. The choice of functional units influences results, highlighting the importance of considering multiple units in assessing organic food’s environmental footprint. This study emphasizes the necessity for comprehensive assessments at both product and diet levels to support informed decisions.
      [Hashemi, F. et al. (2024) Organic food has lower environmental impacts per area unit and similar climate impacts per mass unit compared to conventional, Communications Earth & Environment. Available at: https://www.nature.com/articles/s43247-024-01415-6. ]
    • A holistic review on trend, occurrence, factors affecting pesticide concentration, and ecological risk assessment
      Demographic outbursts and increased food demands invoke excessive use of pesticides in the agricultural field for increasing productivity which leads to the relentless decline of riverine health and its tributaries. These tributaries are connected to a plethora of point and non-point sources that transport pollutants including pesticides into the Ganga river's mainstream. Simultaneous climate change and lack of rainfall significantly increase pesticide concentration in the soil and water matrix of the river basin. This paper is intended to review the paradigm shift of pesticide pollution in the last few decades in the river Ganga and its tributaries. Along with this, a comprehensive review suggests the ecological risk assessment method which facilitates policy development, sustainable riverine ecosystem management, and decision-making. Before 2011, the total mixture of Hexachlorocyclohexane was found at 0.004-0.026 ng/mL in Hooghly, but now, the concentration has increased up to 0.465-4.132 ng/mL. Aftermath of critical review, we observed maximum residual commodities and pesticide contamination reported in Uttar Pradesh > West Bengal > Bihar > Uttara Khand possibly because of agricultural load, increasing settlement, and incompetency of sewage treatment plant in the reclamation of pesticide contamination.
      [Singh, R.P., Mahajan, M., Gandhi, K., Gupta, P.K., Singh, A., Singh, P., Singh, R.K. and Kidwai, M.K., 2023. Environmental Monitoring and Assessment, 195(4), p.451.]
    • A review on arsenic in the environment: contamination, mobility, sources, and exposure
      Arsenic is one of the regulated hazard materials in the environment and a persistent pollutant creating environmental, agricultural and health issues and posing a serious risk to humans. In the present review, sources and mobility of As in various compartments of the environment (air, water, soil and sediment) around the World are comprehensively investigated, along with measures of health hazards. Multiple atomic spectrometric approaches have been applied for total and speciation analysis of As chemical species. The LoD values are basically under 1 μg L−1, which is sufficient for the analysis of As or its chemical species in environmental samples. Both natural and anthropogenic sources contributed to As in air, while fine particulate matter tends to have higher concentrations of arsenic and results in high concentrations of As up to a maximum of 1660 ng m−3 in urban areas. Sources for As in natural waters (as dissolved or in particulate form) can be attributed to natural deposits, agricultural and industrial effluents, for which the maximum concentration of 2000 μg L−1 was found in groundwater. Sources for As in soil can be the initial contents, fossil fuel burning products, industrial effluents, pesticides, and so on, with a maximum reported concentration up to 4600 mg kg−1. Sources for As in sediments can be attributed to their reservoirs, with a maximum reported concentration up to 2500 mg kg−1. It is notable that some reported concentrations of As in the environment are several times higher than permissible limits. However, many aspects of arsenic environmental chemistry including contamination of the environment, quantification, mobility, removal and health hazards are still unclear.
      [Patel, K.S. et al. (2023) A review on arsenic in the environment: Contamination, mobility, sources, and exposure, RSC advances. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10020839/. ]
    • Directly Fluorinated Containers as a Source of Perfluoroalkyl Carboxylic Acids
      Direct fluorination of plastics is performed to impart chemical resistance via exposure of polyethylene to fluorine gas to produce a fluorine-modified surface layer. Leaching experiments were performed on a directly fluorinated container under various conditions and with different matrices, including foodstuffs. The average sum of per- and polyfluoroalkyl substances (PFAS) concentrations measured from extraction of a fluorinated container was 63.75 ± 13.2 ng/g plastic. Seven-day leaching experiments of fluorinated containers with water, methanol, and acetone produced sums of PFAS concentrations that ranged from 0.99 to 66.92 ng/g plastic. Leaching experiments with food matrices produced sums of PFAS concentrations ranging from 2.66 to 7.19 ng/g plastic. A subset of samples subjected to leaching at elevated temperatures generated sums of PFAS concentrations up to 830% higher. In all experiments, short-chain perfluoroalkyl carboxylic acids (PFCAs) were detected in the highest frequencies and concentrations with analyte concentration decreasing as chain length increased. An estimate for PFAS released into food ranged from 0.77 to 2.68 ng/kg body weight per week, showing ingestion of food stored in these containers could be a significant source of exposure. Based on the large number of applications where directly fluorinated containers find use, the observation of PFAS migration suggests use regulations are warranted, and future studies should explore their fate when disposed or recycled.
      [Whitehead, H.D. and Peaslee, G.F., 2023. Environmental Science & Technology Letters, 10(4), pp.350-355.]
    • Driving factors on accumulation of cadmium, lead, copper, zinc in agricultural soil and products of the North China Plain
      The accumulation of heavy metals in agricultural soils concerns food security. By using the Geographical Detector, this study investigated the influence of six types of factors (eleven factors) on the accumulation of Cd, Pb, Cu, Zn in agricultural soil and products of the North China Plain and confirmed the dominant factor. The results showed that heavy metals had accumulated in regional agricultural soils and the accumulation of Cd was severe. The accumulation of heavy metals was significantly influenced by policy factors (the management and reduction in usage of fertilizers and pesticides), fertilization factors (application of organic and chemical fertilizers), pesticide factors (application of herbicide and insecticide) and atmospheric deposition factors (heavy metal concentration in atmospheric deposition). The policy factor dominated the other three types of factors. Atmospheric deposition and the excess application of fertilizers and pesticides directly lead to the accumulation of heavy metals. Due to the high concentrations of heavy metals and abundant application amounts, organic fertilizers have contributed high levels of heavy metals to agricultural soils. This study suggests that formulated fertilization and action plans for pesticide reduction could effectively decrease the accumulation of heavy metals in agricultural soils and products in the study area.
      [Liu, Z., Bai, Y., Gao, J. and Li, J., 2023. Scientific Reports, 13(1), p.7429.]
    • Interactions of Microplastics with Pesticides in Soils and Their Ecotoxicological Implications

      Abstract

      In the middle of the 20th century, the production of plastics exploded worldwide because of their low cost and the versatility of their applications. However, since plastic debris is highly resistant to environmental degradation, a growing presence of plastics in all the ecosystems has been confirmed. Among them, plastic particles < 5 mm, also known as microplastics (MPs), are of special concern because they are dispersed in aerial, terrestrial and aquatic environments, being the soil the main environmental sink of these contaminants. Due to their large specific surface area and hydrophobicity, MPs are considered good adsorbents for other environmental organic pollutants also present in terrestrial ecosystems, such as pharmaceuticals, personal-care products or pesticides with which they can interact and thus modify their environmental fate. In this review article, we examine the recent literature (from 2017 to 2022) to get a better understanding of the environmental fate of pesticides in soil (adsorption, mobility and/or degradation) when they are simultaneously present with MPs and the ecological risks on living organisms of the interactions between MPs and pesticides in soil. More studies are needed to fully understand the toxicological impact of the copresence in soil of pesticides and MPs.

      [Peña, A., Rodríguez-Liébana, J.A. and Delgado-Moreno, L. (2023) ‘Interactions of microplastics with pesticides in soils and their ecotoxicological implications’, Agronomy, 13(3), p. 701. doi:10.3390/agronomy13030701. ]
    • Metabolic Consequences of the Water We Drink: A Study Based on Field Evidence and Animal Model Experimentation
      The effect of the chronic consumption of water contaminated with residual concentrations of DDT's metabolites (DDD-dichlorodiphenyldichloroethane and DDE-dichlorodiphenyldichloroethylene) found in the environment were evaluated on the biometric, hematological and antioxidant system parameters of the hepatic, muscular, renal and nervous tissues of Wistar rats. The results showed that the studied concentrations (0.002 mg.L-1 of DDD plus 0.005 mg.L-1 of DDE) could not cause significant changes in the hematological parameters. However, the tissues showed significant alteration in the activity of the antioxidant system represented by the increase in the activity of the enzymes gluthathione S-transferases in the liver, superoxide dismutase in the kidney, gluthathione peroxidase in the brain, and several changes in enzymatic activity in muscle (SOD, GPx and LPO). The enzymes alanine aminotransaminase (ALT) and aspartate aminotransaminase (AST) were also evaluated for the amino acids' metabolism in the liver, with ALT showing a significant increase in the exposed animals. In the integrative analysis of biomarkers (Permanova and PCOA), the studied concentrations showed possible metabolic changes and damage to cellular structures evidenced by increased oxidative stress and body weight gain among the treated animals. This study highlights the need for further studies on the impact of banned pesticides still present in soils that may induce adverse effects in organisms that may prevail in future generations and the environment.
      [Wolfart, J.C., Theodoro, J.L., Silva, F.C., de Oliveira, C.M.R., Ferreira, N.G. and Bittencourt Guimarães, A.T., 2023. Toxics, 11(4), p.315.]
    • Outside the Safe Operating Space of a New Planetary Boundary for Per- and Polyfluoroalkyl Substances (PFAS)
      It is hypothesized that environmental contamination by per- and polyfluoroalkyl substances (PFAS) defines a separate planetary boundary and that this boundary has been exceeded. This hypothesis is tested by comparing the levels of four selected perfluoroalkyl acids (PFAAs) (i.e., perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexanesulfonic acid (PFHxS), and perfluorononanoic acid (PFNA)) in various global environmental media (i.e., rainwater, soils, and surface waters) with recently proposed guideline levels. On the basis of the four PFAAs considered, it is concluded that (1) levels of PFOA and PFOS in rainwater often greatly exceed US Environmental Protection Agency (EPA) Lifetime Drinking Water Health Advisory levels and the sum of the aforementioned four PFAAs (Σ4 PFAS) in rainwater is often above Danish drinking water limit values also based on Σ4 PFAS; (2) levels of PFOS in rainwater are often above Environmental Quality Standard for Inland European Union Surface Water; and (3) atmospheric deposition also leads to global soils being ubiquitously contaminated and to be often above proposed Dutch guideline values. It is, therefore, concluded that the global spread of these four PFAAs in the atmosphere has led to the planetary boundary for chemical pollution being exceeded. Levels of PFAAs in atmospheric deposition are especially poorly reversible because of the high persistence of PFAAs and their ability to continuously cycle in the hydrosphere, including on sea spray aerosols emitted from the oceans. Because of the poor reversibility of environmental exposure to PFAS and their associated effects, it is vitally important that PFAS uses and emissions are rapidly restricted.
      [Cousins, I.T., Johansson, J.H., Salter, M.E., Sha, B. and Scheringer, M. Environmental Science & Technology.]
    • Response of microbial antibiotic resistance to pesticides: An emerging health threat
      The spread of microbial antibiotic resistance has seriously threatened public health globally. Non-antibiotic stressors have significantly contributed to the evolution of bacterial antibiotic resistance. Although numerous studies have been conducted on the potential risk of pesticide pollution for bacterial antibiotic resistance, a systematic review of these concerns is still lacking. In the present study, we elaborate the mechanism underlying the effects of pesticides on bacterial antibiotic resistance acquisition as well as the propagation of antimicrobial resistance. Pesticide stress enhanced the acquisition of antibiotic resistance in bacteria via various mechanisms, including the activation of efflux pumps, inhibition of outer membrane pores for resistance to antibiotics, and gene mutation induction. Horizontal gene transfer is a major mechanism whereby pesticides influence the transmission of antibiotic resistance genes (ARGs) in bacteria. Pesticides promoted the conjugation transfer of ARGs by increasing cell membrane permeability and increased the proportion of bacterial mobile gene elements, which facilitate the spread of ARGs. This review can improve our understanding regarding the pesticide-induced generation and spread of ARGs and antibiotic resistant bacteria. Moreover, it can be applied to reduce the ecological risks of ARGs in the future.
      [Qiu, D. et al. (2022) Response of microbial antibiotic resistance to pesticides: An emerging health threat, Science of The Total Environment. Available at: https://www.sciencedirect.com/science/article/abs/pii/S0048969722051567. ]
    • An evaluation of biological soil health indicators in four long-term continuous agroecosystems in Canada
      The soil microbial community (SMC) and soil organic matter (SOM) are inherently related and are sensitive to land-use changes. Microorganisms regulate essential soil functions that are key to SOM dynamics, whereas SOM dynamics define the SMC. To expand our understanding of soil health, we evaluated biological and SOM indicators in long-term (18-yr) continuous silage corn (Zea mays L.), continuous soybean [Glycine max (L.) Merr.], and perennial grass ecosystems in Ontario, Canada. The SMC was evaluated via ester-linked fatty acid methyl ester (EL-FAME) and amplicon sequencing. Soil organic matter was evaluated via a new combined enzyme assay that provides a single biogeochemical cycling value for C, N, P, and S cycling activity (CNPS), as well as loss-on-ignition, permanganate oxidizable C (POXC), and total C and N. Overall, soil health indicators followed the trend of grasses > corn > soybean. Grass systems had up to 8.1 times more arbuscular mycorrhizal fungi, increased fungal/bacteria ratios (via EL-FAME), and higher microbial diversity (via sequencing). The POXC was highly variable within treatments and did not significantly differ between systems. The novel CNPS activity assay, however, was highly sensitive to management (up to 2.2 and 3.2 times higher under grasses than corn and soybean, respectively) and was positively correlated (ρ > .92) to SOM, total C, and total N. Following the “more is better” model, where higher values of the measured parameters indicate a healthier soil, our study showed decreased soil health under monocultures, especially soybean, and highlights the need to implement sustainable agriculture practices that maintain soil health.
      [Pérez‐Guzmán, L., Phillips, L.A., Seuradge, B.J., Agomoh, I., Drury, C.F. and Acosta‐Martínez, V. Agrosystems, Geosciences & Environment, 4(2), p.e20164.]
    • Winter cover crops shape early-season predator communities and trophic interactions
      Despite the dynamic nature of annual cropping systems, few studies have investigated how the structure of predator communities and their interactions with prey corresponds with crop seasonality. Adding winter habitat, such as cover crops, improves soil health and likely contributes seasonal habitat availability for arthropod communities. Stable habitat may lead to functionally diverse predatory communities and their associated ecosystem services, such as biological control. Here, we estimated predatory community functional changes based on foraging traits determined by molecular gut–content analysis (MGCA) in response to winter cover crops (rye and crimson clover) in a cotton agroecosystem. Predators were collected from replicated 1-ha experimental field plots during each major stage of crop development in 2017 and 2018, and MGCA was used to estimate predator roles and responses to cover crop treatments. Cotton planted into a rye cover crop residue promoted unique predator communities in the early and mid-season as compared to no-cover fields. Correspondingly, we observed dissimilar prey consumption among cover crop treatments. Winter cover crops led to an increase in consumption of alternative prey and incidental pests by natural enemies on seedling cotton and encouraged high predator diversity that aligns temporally with potential early-season pest outbreaks. Therefore, cover crops commonly employed for soil health and erosion benefits also contribute to pest management by providing habitat and alternative prey resources that boost early-season predatory arthropod communities.
      [Bowers, C., Toews, M.D. and Schmidt, J.M. Ecosphere, 12(7), p.e03635.]
    • Long-term effects of neonicotinoid insecticides on ants
      The widespread prophylactic usage of neonicotinoid insecticides has a clear impact on non-target organisms. However, the possible effects of long-term exposure on soil-dwelling organisms are still poorly understood especially for social insects with long-living queens. Here, we show that effects of chronic exposure to the neonicotinoid thiamethoxam on black garden ant colonies, Lasius niger, become visible before the second overwintering. Queens and workers differed in the residue-ratio of thiamethoxam to its metabolite clothianidin, suggesting that queens may have a superior detoxification system. Even though thiamethoxam did not affect queen mortality, neonicotinoid-exposed colonies showed a reduced number of workers and larvae indicating a trade-off between detoxification and fertility. Since colony size is a key for fitness, our data suggest long-term impacts of neonicotinoids on these organisms. This should be accounted for in future environmental and ecological risk assessments of neonicotinoid applications to prevent irreparable damages to ecosystems.
      [Schläppi, D., Kettler, N., Straub, L., Glauser, G. and Neumann, P., 2020. Communications biology, 3(1), pp.1-9.]
    • Occurrence and Ecological Impacts of Microplastics in Soil Systems: A Review
      Microplastics, as a group of emerging contaminants, are receiving growing attention. During the last decade, their occurrence and toxicity in aquatic ecosystems have been intensively studied and reviewed, but less attention has been paid on soil ecosystems. Given the importance of soil ecosystems and the call for increasing research on soil from scientific communities, it is predicted that relevant studies will boom in the following years. The present review intends to provide a comprehensive overview of current knowledge on microplastic pollution in soil environments. We critically summarize the source, contamination level and fate of microplastics in (industrial and arable) soils. Then, we thoroughly describe what effects have been observed on soil microbes, animals and plants, and analyze what insights we can get from available information. Finally, we identify knowledge gaps that need to be filled and give suggestions for future research.
      [Zhu, F. et al. (2019) Occurrence and ecological impacts of microplastics in soil systems: A Review, Bull Environ Contam Toxicol. Available at: https://pubmed.ncbi.nlm.nih.gov/31069405/. ]
    • Microplastics in soils: Analytical methods, pollution characteristics and ecological risks
      Microplastics are emerging persistent contaminants of increasing concern. Although microplastics have been extensively detected in aquatic environments, their occurrence in soil ecosystems remains largely unexplored. This review focused on recent progress in analytical methods, pollution characteristics and ecological effects of microplastics in soils. In spite of the presence of microplastics in soils, no standardized methods are available for the quantification. Uniform protocols including microplastic extraction and identification are urgently needed to develop. In soil environments, main sources of microplastics include mulching film, sludge, wastewater irrigation and atmospheric deposition. The fate of microplastics is closely related to soil physio-chemistry and biota. Existing evidence shows that microplastics can influence soil biota at different trophic levels, and even threaten human health through food chains. Therefore, further research is needed to fully reveal the fate and ecological risks of microplastics in soils; and necessary action is required to control microplastic pollution in terrestrial ecosystems.
      [He, D. et al. (2018) Microplastics in soils: Analytical methods, pollution characteristics and ecological risks, TrAC Trends in Analytical Chemistry. Available at: https://www.sciencedirect.com/science/article/pii/S0165993618304102?ref=pdf_download&fr=RR-7&rr=87d9ad93cbbf2f24. ]