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. 

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.

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