What do pesticides do to soil

We defined soil organisms as any non-target invertebrate that has egg, larval, or immature development in the soil Paoletti and Purrington, Many soil-associated invertebrates such as various species of Arachnids, Diptera, or Hymenoptera were therefore not included.

In addition, no aquatic organisms or terrestrial microbial organisms such as bacteria and fungi were included. The soil organisms that fit our criteria from the relevant studies are organized by taxa in the Results section and include Oligochaeta earthworms , Enchytraeidae potworms , Nematoda roundworms , Tardigrada water bears , Acari mites , Myriapoda centipedes and millipedes , Isopoda woodlice , Collembola springtails , Protura coneheads , Isoptera termites , Coleoptera beetles , Formicidae ants , Bombus spp.

We identified and extracted the relevant tested parameters in each study. All tested parameters measured a specific endpoint following exposure of a specific organism to a specific pesticide. For instance, if a study tested how three different pesticides chlorpyrifos, imidacloprid, and permethrin affected two endpoints mortality and DNA damage on one species Caenorhabditis elegans , then we would be able to extract six unique tested parameters, any of which could result in a negative effect, positive effect or no significant effect to the tested species.

In studies that analyzed multiple substrates, we only entered data from soil tests but also included studies if they only utilized surrogate substrates, such as filter paper. Similarly, if there were multiple time periods utilized to determine LC50 or EC50, we reported data from only the standard 48 h or seven days, whichever was relevant.

If there were multiple soil types, temperatures, pesticide concentrations, or moisture contents, we extracted the full data range rather than separating each variable as its own tested parameter. For instance, if three different concentrations of chlorpyrifos were tested on C. If any of the three concentrations caused a positive or negative effect on C. If all three concentrations caused no significant effect, then it was categorized as having no effect.

We considered an effect negative or positive if the authors reported a statistically significant change from that of the control. If a study reported an effect on an endpoint over a time course, we considered the effect positive or negative if there was a significant effect in any of the tested times e.

A small minority of studies lacked statistical analyses. For instance, some studies used specific thresholds to determine significance e. We classified tested endpoints into nine major categories that measured the following:. Biomass — weight of organisms. Behavior — behavioral responses, including avoidance, mounding or burrowing activity, litter decomposition, food consumption and predation on or parasitism of target pests, cast or fecal production, locomotor functioning, defensiveness and aggression, and foraging and flight efficiency.

Reproduction — fecundity, reproductive anatomy and function, and offspring production, including egg laying rate, hatching rate, juvenile number, larval ejection, ovary development and sperm deformation, sex ratio, brood number and production, sterility, and viable brood cells. Biochemical biomarkers — biochemical or molecular responses from toxic exposure, including oxidative stress ROS , enzymatic, protein, and lipid activity or content, gene expression, cellular energy allocation or energy available, mitochondrial response, metabolism, neutral red retention time NRRT , DNA damage, and synapsin levels.

Growth — weight and development of individuals, including adults and juveniles, molting rate, larval growth, and cocoon production. Richness and diversity — community structure and composition, including richness, diversity, and evenness. A total of laboratory and field studies fit our criteria, yielding 2, tested parameters representing unique species, taxa, or combined taxa of soil organisms and different pesticide active ingredients or unique mixtures of active ingredients.

The majority of studies tested the impact of insecticides on 1, tested parameters, followed by herbicides, fungicides, bactericides, and pesticide mixtures with 67, 55, 49, and 2 studies looking at , , , and 26 tested parameters, respectively. Overall, we found that pesticides negatively affected By pesticide type, The impact of pesticide mixtures depended on the type; of the 49 mixtures, those consisting of insecticides negatively affected tested parameters Table 1.

The number of tested parameters par. Bactericides generally resulted in fewer negative results in lab studies; however, they were underrepresented compared to other pesticide types.

Figure 1. Percentage of tested parameters showing negative, positive, and no significant effects on soil invertebrates for each pesticide type from laboratory studies, field studies, and total studies. Organophosphates and neonicotinoids were the most studied classes of insecticides; of herbicides, phosphonoglycines glyphosate and triazines; and of fungicides, inorganic compounds such as copper and zinc, as well as conazoles Supplementary Table 1.

Figure 2. Percentage of tested parameters showing negative, positive, and no significant effects on soil invertebrates for all pesticides studied and for individual pesticide types and classes. Of endpoint categories, structural changes and biochemical biomarkers were the most impacted by pesticides followed by reproduction, mortality, behavior, growth, richness and diversity, abundance, and lastly, biomass Table 2.

Supplementary Table 2 presents the effects of the most studied classes on the endpoint categories. Table 2. Overall trends by taxa revealed that Coleoptera beetles were more negatively affected by insecticides Of insecticides, neonicotinoids were the most detrimental to Coleoptera, with Enchytraeids potworms were one of the only taxa that were more negatively impacted following exposure to herbicides Collembola were more negatively affected when exposed to fungicides A total of studies with 1, tested parameters conducted in the lab fit our criteria.

The endpoints most studied in the lab were biochemical biomarkers , mortality , reproduction , behavior , growth , and structural changes 36 Supplementary Table 3. Of taxa, earthworms Oligochaeta accounted for Collembola, Isopoda, Acari, and Bombus spp. There were fewer than 30 tested parameters for the remaining taxa — Coleoptera, Formicidae, parasitic wasps, non- Bombus ground-nesting bees, Isoptera, and Nematoda.

Pesticides negatively affected A total of studies containing 1, tested parameters conducted in a field or semi-field setting fit our criteria. The endpoints most studied in field settings were abundance , mortality , behavior , reproduction 66 , growth 66 , biomass 55 , richness and diversity 34 , and biochemical biomarkers 26 Supplementary Table 4. Coleoptera was the most studied taxon in field studies tested parameters , followed closely by Oligochaeta tested parameters.

Acari, Collembola, Bombus spp. There were fewer than 30 tested parameters for the remaining taxa — parasitic wasps, Isopoda, Isoptera, Nematoda, Tardigrada, and Myriapoda. Additionally, 56 tested parameters were associated with mixed organism groups.

Enchytraeids potworms were analyzed in 38 lab studies with tested parameters, of which pesticides negatively affected Specifically, insecticides negatively affected Of endpoints, pesticides negatively affected biochemical biomarkers, reproduction, survival, and behavior Two tested parameters analyzed growth, with copper oxychloride negatively affecting worm body mass and a mixture of epoxiconazole and dimoxystrobin having no effect Bart et al.

All other Oligochaetes, primarily Lumbricidae, but also Eudrilidae, Glossoscolecidae, Megascolecidae, and Moniligastridae were analyzed in lab studies with 1, tested parameters. Biochemical biomarkers, which included subcellular events such as enzyme activity, membrane stability, gene expression, metabolism, DNA damage, and general oxidative stress, were the most studied parameters and were negatively affected in Pesticides negatively impacted earthworm survival, reproduction, growth, and structural changes in Behavior, which included feeding rate, activity, burrowing, cast production, litter decomposition, avoidance, and respiration, was negatively affected in Pesticides negatively affected potworms in Specifically, fungicides negatively affected Potworm reproduction was negatively affected in six of eight tested parameters and feeding behavior was reduced by imidacloprid and cyfluthrin seed coatings, but not by the fungicide, thiram Supplementary Table 4 Larink and Sommer, Earthworm mortality, abundance, and biomass were negatively affected in Earthworm richness and diversity and behaviors like avoidance of pesticides, surface and cumulative activity, burial of organic matter, cast production, feeding activity, and litter decomposition were also negatively impacted in about half to two-thirds of the tested parameters.

Pesticides negatively impacted earthworm reproduction in Imidacloprid Kreutzweiser et al. Pesticides negatively affected nematodes in Specifically, insecticides and fungicides negatively affected The survival of various nematode species was reduced by the fungicide fludioxonil Haegerbaeumer et al.

Nematode reproduction was negatively affected in six of seven tested parameters, by the fungicide fludioxonil Haegerbaeumer et al. Biochemical biomarkers were negatively affected in all of six tested parameters Supplementary Table 3 ; specifically, oxidative stress response in Caenorhabditis elegans was induced by the herbicides, glyphosate and paraquat Kronberg et al.

Growth was negatively affected in all of five tested parameters; acetochlor reduced growth in Acrobeloides nanus , Pristionchus pacificus, and C. In seven field studies, pesticides negatively affected nematodes in Carbendazim reduced survival Burrows and Edwards, , glyphosate reduced biomass Hagner et al.

Nematode diversity was also reduced by 1,3-Dichloropropene, which also was found to negatively affect Tardigrade water bear density Carrascosa et al. Pesticides negatively affected mites in Specifically, insecticides negatively impacted Mite survival and reproduction were negatively affected Acari also avoided soils treated with chlorpyrifos, dimethoate, deltamethrin, copper, Owojori et al.

Pesticide impacts to mite abundance varied between species, but was significantly reduced Oribatid mite reproduction was negatively impacted in two of five tested parameters and Oribatid mite diversity was negatively impacted by exposure to a combination of mancozeb, copper oxychloride, and metalaxyl Al-Assiuty et al.

The insecticide deltamethrin negatively affected Diplopoda in three tested parameters Supplementary Table 5 , causing a significant reduction in survival and neurological functioning, as well as altering millipede behavior by causing agitation, release of defensive secretion, gonopod externalization, and hemolymph leakage Francisco et al. Pesticides had a negative effect in Diflubenzuron and mancozeb decreased Myriapod abundance by Monuron reduced overall Diplopod abundance, while atrazine had no significant effect Fox, Imidacloprid Peck, and a mixed pesticide regimen Lundgren et al.

In pesticide-treated vineyards, the relative abundance of Diplopoda, including Julidae sp. Pesticides negatively affected Isopods in Survival of Porcellio scaber, P. Isopod growth was also negatively impacted in four out of seven tested parameters, reduced by imidacloprid Drobne et al. Reproduction was negatively affected in two out of three tested parameters by dimethoate Fischer et al. Pesticides negatively affected Isopods in one of four tested parameters from three field studies Supplementary Table 6.

Glyphosate did not induce avoidance behavior or reduce reproduction in P. Pesticides negatively affected springtails in Collembola mortality was negatively affected in Pesticides negatively impacted Collembola survival was negatively impacted by dimethoate Joy and Chakravorty, and chlorpyrifos Wiles and Frampton, , but not cypermethrin Wiles and Frampton, and collembola abundance was reduced Chlorpyrifos significantly reduced springtail species richness in one study Fountain et al.

Ethoprophos reduced biomass of F. In the only study of another Order of Entognatha — Protura — abundance was unaffected by imidacloprid Peck, One lab study with termites found that streptomycin induced aggressive fighting behavior between individual termites in the same nest Gao et al.

Insecticides negatively impacted termites in In one tested parameter, chlorpyrifos significantly reduced termite abundance De Silva et al. Fipronil also reduced wood and cardboard bait consumption in Microcerotermes, Armitermes, and Drepanotermes termites in multiple soil types Steinbauer and Peveling, Pesticides negatively affected ground beetles Carabidae in Thiamethoxam seed treatment significantly reduced Coleoptera survival Douglas et al.

Beetles, primarily in the family Carabidae, but also Staphylinidae, Latridiidae, Cryptophagidae, Tenebrionidae, Cleridae, Nitidulidae, and Elateridae, were the most represented taxa in field studies and pesticides negatively affected Beetle abundance was reduced in Beetle behavior, such as feeding rate, predation, avoidance, and locomotory response were negatively affected in Beetle richness and diversity, as well as growth parameters measuring larval development, body size, muscle mass, and lipid mass were negatively affected in two of seven and However, beetle enzymatic activity, hemocyte count, and plasmatic basal and phenoloxidase activities, were negatively affected in five out of six tested parameters Supplementary Table 4.

Of two lab studies with eight tested parameters on ant behavior, insecticides negatively affected seven, or Environmentally relevant concentrations of imidacloprid impaired Pogonomyrmex occidentalis Cresson navigation and foraging success Sappington, and the activity and foraging behavior of Lasius flavus F. Specifically, a significant increase in aggressive behavior in L. Pesticides negatively affected ants in Ant abundance was significantly reduced Behavior was studied in three tested parameters with two negative effects Supplementary Table 4 ; clothianidin and bifenthrin applied together significantly reduced ant predation of black cutworm eggs, and bifenthrin significantly reduced the mound-building activity of L.

Pesticides negatively affected bumble bees in Insecticides negatively impacted Bumble bee survival was significantly reduced by pesticides in Of the two biochemical biomarker parameters, clothianidin and thiamethoxam altered B.

Herbicides were not studied and fungicides had Neonicotinoids were present in Abundance, survival, and reproduction were significantly reduced in Nest condition was severely impacted by imidacloprid, while bumble bee biomass was not significantly affected by imidacloprid or chlorpyrifos Moffat et al.

Pesticides negatively impacted bumble bee behavior in Pesticides also negatively affected Insecticides negatively affected non- Bombus ground-nesting bees in seven Specifically, survival was significantly reduced in all tests from exposure to permethrin, mexacarbamate, aminocarb, fenitrothion, carbaryl and spinosad Helson et al.

Spinosad had no significant effect on the feeding rate of Nomia melanderi Cockerell Halictidae Mayer et al. Pesticides negatively affected non- Bombus ground-nesting bees in Bee survival was negatively affected in Both neonicotinoids Main et al. Many parasitic wasps develop in the soil, including Trybliographa rapae Westwood Figitidae , which was analyzed in one lab study with four tested parameters.

Although T. The survival of Tiphia vernalis Rohwer Tiphiidae was reduced by bifenthrin, carbaryl, chlorpyrifos, imidacloprid, oryzalin, pendimethalin, chlorothalonil, thiophanate-methyl, and a mixture of 2,4-D and dicamba, but not halofenozide Oliver et al. Imidacloprid reduced T. Mixed groups of soil organisms were analyzed in 19 studies with 56 tested parameters, of which pesticides negatively affected Soil taxa abundance and richness were negatively affected in Litter decomposition and feeding rate behaviors were significantly reduced in In reviewing studies on pesticide impacts to soil invertebrates, we found that negative effects dominated, with These findings indicate that a wide variety of soil-dwelling invertebrates display sensitivity to pesticides of all types and support the need for pesticide regulatory agencies to account for the risks that pesticides pose to soil invertebrates and soil ecosystems.

Insecticides were by far the most-studied pesticide type and, unsurprisingly, because they are designed to target invertebrates, had the largest negative impact on soil invertebrates of any pesticide type analyzed.

Bumble bees Bombus spp. Some of this variability likely stems from fewer studies on herbicide and fungicide impacts compared to insecticides and, as a result, very few tested parameters for some taxa Table 1. These results indicate that, in general, soil invertebrates are more variable in their sensitivity to fungicides and herbicides than insecticides.

There were too few studies that met our search criteria to identify clear trends regarding the impact of bactericides on soil invertebrates, likely because we did not include research on microorganisms like bacteria or fungi.

Negative effect percentages of pesticide mixtures varied between We found that positive effects were rare 1. A positive effect indicates a benefit to one soil organism that may come at the detriment to other soil taxa or soil ecosystem functioning. For example, abundance of certain soil taxa could increase if a pesticide reduces competitors or predators, either through mortality or emigration from the area.

Our search criteria only identified three studies that tested the sensitivity of soil invertebrates to commonly used soil fumigants, specifically 1,3-D, dazomet, chloropicrin and metam sodium. Of the nine tested parameters involving fumigants, seven resulted in negative effects to non-target soil invertebrates. The lack of available studies on harm from soil-applied fumigants to non-target invertebrates indicates that this is an area in need of more research. Few studies measure the effects of pesticide mixtures as opposed to individual active ingredients, though research shows that mixtures of pesticide residues in the soil are the rule rather than the exception Silva et al.

Nearly all corn grown in the United States is treated with multiple pesticides Douglas and Tooker, ; Lamichhane et al. We included pesticide mixture studies in our analysis, which surprisingly had fewer overall negative effects than single pesticides.

This is likely because mixture studies were overwhelmingly done in a field or semi-field setting rather than a laboratory. Other variables could also contribute to the overall lower negative effect percentage of mixtures. For instance, mixture studies are often done with concentrations of individual components that are known to not produce an effect individually in order to maximize the ability to identify interactive effects Kortenkamp, Furthermore, there was considerable variability in the outcome of mixture experiments based on pesticide type analyzed see Results Section.

Therefore, we caution against comparing the negative effect percentage for mixture studies with those of individual pesticide types in this analysis. Ultimately, considering that environmental exposure to pesticide mixtures is the rule and not the exception, research on pesticide mixtures is a major gap in the literature that we hope receives future focus. Overall, we found fewer negative impacts of pesticides in field studies compared to laboratory studies.

One likely reason for this finding is that the pesticide concentrations used in lab studies were generally higher, while field studies often applied concentrations at or below the recommended use rate. Higher concentrations of pesticides are more often associated with negative effects on soil organisms Puglisi, For instance, a study on the effects of pyrimethanil on Enchytraeids conducted across two labs in Portugal and Germany found contrasting results based on the tested pesticide concentration Bandow et al.

Due to the scope of this review, we did not identify the concentrations expected to be encountered in the environment for every pesticide used in each study. Therefore, this review is inclusive of the wide variety of exposure concentrations found in the literature and is focused on identifying hazards, not necessarily risks. In addition, uncontrolled, confounding environmental variables could provide some buffering capacity for pesticide effects in field and semi-field studies.

Climatic conditions and various seasonal or yearly variations to the agricultural setting outside of pesticide application, such as cropping system changes or irrigation, make it difficult to fully assess pesticide effects under short-term trials Ewald et al. Significant differences in the soil microbial community structure were observed when pyrimethanil was applied during heavy rainfalls versus drought Ng et al.

While laboratory studies often use artificial soil or a standardized natural soil, agricultural soil environments vary widely in factors such as organic matter, water holding capacity, and pH Amorim et al. Additionally, ecotoxicology tests in the lab may use contact filter paper instead of soils, to which soil organisms typically show much higher sensitivity to pesticides.

For example, the LC50 for earthworms treated with cypermethrin in artificial soils was 9. Despite the major advantage of field studies being conducted under more realistic conditions than laboratory studies, there are some downsides to relying on them exclusively. Since the complex logistics and expensive nature of field experiments can lead to lower sample sizes and fewer replicates, they can often lack a high statistical power. This can lead to statistical results that are highly variable between studies even when the overall effects are more-or-less consistent, leading researchers to advise conservative interpretations of non-significant results in low-powered field studies Douglas and Tooker, Some endpoints — such as reproduction or individual growth — or organisms that are smaller or less abundant can be difficult to study in the field.

Additionally, since pesticides are generally approved for use in different regions with highly variable agricultural practices, geography, precipitation, temperature, air quality, background soil contamination, soil mineral content, pH and organic matter, field studies done in one region may not be representative of effects in another region. The majority of field studies we found took place in Europe and the United States, while very few field studies were conducted in countries from other continents.

The disproportionate data from these temperate regions could over- or underestimate the risk of pesticides to soil organisms in other regions of the world, or even subregions in the studied countries.

Controlling many of the fluctuating variables found in field tests in a laboratory setting can be useful, and both types of studies should be considered helpful in identifying potential harms that could come from pesticide use in or near soil.

The most sensitive endpoint category was structural changes, followed closely by biochemical biomarkers, then reproduction, mortality, behavior, growth, richness and diversity, abundance, and lastly, biomass Table 2.

All observable effects in a whole organism are preceded by subcellular events which can be measured in biochemical biomarker tests, yet all subcellular events will not necessarily lead to these larger, gross changes. Therefore, having the negative effect percentage of tested parameters gradually decrease from biochemical effects to sublethal effects to lethal effects to more macro-changes like richness and diversity was expected.

Instead, when an organism is engaged in the detoxification process of pollutants in order to ensure survival, normal functions such as reproduction, growth, and feeding or burrowing behaviors are likely to suffer Pelosi et al.

For example, earthworms exposed to copper fungicides entered quiescence — a period in which development is suspended — in order to resist contamination, which resulted in a significant reduction of biomass Bart et al. As a test metric, avoidance behavior has high variability and lower sensitivity than other endpoints and has been suggested for better use as a screening evaluation of soil contamination Loureiro et al.

Observation of avoidance may explain a reduction in abundance or species richness. However, for taxa that do not avoid pesticide treated soil, reductions in abundance may result from higher mortality.

There can also be false negatives in avoidance tests; for example, dimethoate did not cause avoidance behavior in Folsomia candida but did cause stress or paralysis that prevented movement Pereira et al. Additionally, certain taxa like Annelids and Isopods possess chemical receptors that allow them to detect and therefore respond to pesticides more readily than other taxa Loureiro et al. Soil toxicology research tends to focus on the impacts of direct exposure and largely ignores the indirect effects on ecosystems when soil organisms are harmed.

As such, our review was only able to account for the direct, measured harm to soil organisms and does not account for any additional harm to ecosystems through indirect effects. For instance, herbicides had a greater negative effect on small arthropod population dynamics through changes to surface litter structural complexity, composition, and nutrition than from direct toxicity House et al.

Additionally, the direct effects of pesticides on soil organisms can have indirect consequences to ecosystem functioning on a larger scale, including contaminating or reducing food sources for terrestrial vertebrates such as birds Hallmann et al. The importance of these indirect effects of pesticides are underappreciated and, when unaccounted for, can result in an underestimation of risk posed by pesticide use.

Persistence of pesticides in the soil varies greatly across different environmental conditions, like soil type or temperature, and among different pesticides, with particular classes like neonicotinoids Gibbons et al. Both burrowing soil taxa and those that develop in the soil are likely to be more vulnerable to the effects of soil-persistent pesticides and conditions that contribute to their persistence.

Some studies in our analysis found that soil invertebrates recovered from negative effects after removal from contaminated soil or following a single pesticide application. We chose not to account for recovery in our data because it would have greatly increased the complexity of our analysis, and its relevance under typical agricultural practices is questionable considering the widespread practice of recurring treatments.

For instance, agricultural fields in Great Britain received an average of The United States Department of Agriculture estimates that Washington apples are treated with an average of 51 different pesticides in a total of 6—17 applications per year USDA, East coast apples are also treated 15—25 times with pesticides throughout a given year USDA, With some pesticides persisting in soil for months or years and the real prospect of recurrent pesticidal applications during the growing season in many fields, soil organisms may not fully recover as they might in the lab or following a single application to a field.

Trends in pesticide application methods are also leading to an increase in the potential for soil contamination. Due to widespread harms associated with pesticide drift, mitigation measures are increasingly being adopted in the United States to cut down on atmospheric presence of pesticides. This includes measures that can increase soil deposition to an area, such as increasing spray droplet size, adding anti-drift adjuvants to formulations and lowering boom height U.

EPA, a. In conjunction with other pesticide application methods that have increased considerably, such as pesticide seed treatment Hitaj et al. It has been suggested that recovery of the soil invertebrate community is slow and can take more than 15 years Menta, Therefore, while recovery from some of these sublethal negative effects is possible, it necessarily depends on quick elimination of the soil pesticide followed by a sufficient period for recovery to take place before another application is made.

This will likely vary considerably from field to field. In observing the effects of pesticides on soil organisms, scientists and regulators have tended to focus on a handful of surrogate species that are conducive to studying in a lab or field environment Frampton et al.

Earthworms are the most studied soil organism in ecotoxicology, partially because of their ubiquity in the soil, their pivotal role as ecosystem engineers, and the ease with which they are studied Luo et al. Eisenia spp. Pelosi et al. Earthworms are less sensitive to pesticides than other soil invertebrates in general Frampton et al.

Field studies typically look at diverse soil communities, often with a focus on beneficial predators like ground beetles Carabidae and rove beetles Staphylinidae ; larger taxa that are easier to capture and identify.

Still, there is high variability in sensitivity between beetles, often depending on size and seasonal variations of life cycle; as an example, dimethoate applied at lower rates resulted in harm to smaller species like the Carabids, Agonum dorsale Pontoppidan and Bembidion sp. In general, the smaller and more cryptic Protura, Diplura, Pseudoscorpionida, Symphyla, and Pauropoda are the least commonly investigated soil taxa Menta and Remelli, In our analysis, Protura, Pauropoda, and Tardigrada were each analyzed in only one study Peck, ; Carrascosa et al.

In addition, there were fewer than 20 tested parameters for parasitic wasps, termites, and Myriapods, including millipedes and centipedes. Bumble bees were commonly represented in the studies in our analysis, yet comparatively less negatively impacted by insecticides than other soil taxa. One potential reason is that there was a higher number of field studies for bumblebees compared to other soil taxa, and, as discussed above, field studies tended to reveal fewer negative effects.

Bumble bees are one of the few taxa in our analysis that spend much of their life above ground, sometimes nest above ground, and are eusocial. Thus the exposure potential in bumble bee studies may differ from that of other soil organisms Gradish et al. Non- Bombus ground-nesting bees, though less-studied, were negatively impacted by neonicotinoids and other insecticides at a rate more typical to other taxa in our analysis i.

The European honey bee Apis mellifera is the only terrestrial invertebrate for which the U. EPA requires testing for pesticide toxicity, and only on an acute-contact exposure basis Legal Information Institute, This is the case even for pesticides that are applied directly to the soil. But companies know that these practices are often accompanied by increased pesticide use. When fields are not tilled, herbicides are frequently used to kill weeds, and cover crops are often killed with chemicals before crop planting.

The long-term environmental cost of that failure can no longer be ignored. Protecting them should be a priority, not an afterthought.

And it will require that the EPA take aggressive steps to protect soil health. Nathan Donley is environmental health science director at the Center for Biological Diversity, headquartered in Arizona. His work focuses on U.

Credit: Nick Higgins. Tari Gunstone is a scientist who, as a research assistant at the Center for Biological Diversity, spent more than a year analyzing studies on pesticide impacts to soil health.

Already a subscriber? Sign in. Thanks for reading Scientific American. As little as 0. The remainder contaminates the soil, air and water and can have significant impacts throughout the ecosystem. Pesticides can also linger in the soil for years or decades after they are applied, continuing to harm soil health.

Soil organisms encounter a cocktail of toxic chemicals. Research shows that mixtures of pesticide residues in the soil are the rule, not the exception, since farmers typically use multiple pesticides at once. For example, the U. Department of Agriculture estimates that Washington apples are treated with an average of 51 different pesticides in 6 to 17 applications per year.

Seeds treated with insecticides like neonicotinoids are set right into the soil, and most of the pesticide stays there. Neonicotinoids are particularly harmful to insects. The continued use of toxic chemicals to grow our food undermines the healthy soil ecosystems that sustainable food production depends on.

Despite the known harm pesticides pose to soil life, the U. To protect the long-term health of the soil that feeds us, the EPA must include assessing harm to soil invertebrates in the U.

We know farming practices like composting and cover cropping build healthy soil ecosystems and reduce the need for pesticides in the first place. Yet our farm policies continue to prop up a pesticide-intensive food system. Our results highlight the need for policies that support farmers adopting ecological farming methods that help biodiversity flourish in the soil and above ground.