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:
- 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.
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.
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.
- 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.]
- 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.]
- Outside the Safe Operating Space of a New Planetary Boundary for Per- and Polyfluoroalkyl Substances (PFAS)