(Beyond Pesticides, August 17, 2015) A study published in Scientific Reports has found that glyphosate, the controversial and toxic active ingredient in Roundup, reduces activity and reproduction in two species of earthworms and increases soil nutrient concentrations to dangerous levels. Earthworms are excellent indicators of soil health, and provide vitally important ecosystem services by aerating the soil, cycling nutrients, and increasing soil fertility and microbial activity. The findings are especially alarming because this herbicide has been used globally for decades, and its use has grown exponentially. Earlier this spring, the WHO’s International Agency for Research on Cancer (IARC) classified glyphosate as Group 2a “probable” human carcinogen based on sufficient evidence of carcinogenicity in laboratory animals.
Researchers looked at two species of earthworms: vertically burrowing earthworms (Lumbricus terrestris) and soil dwelling earthworms (Aporrectodea caliginosa). Vertically burrowing earthworms typically feed above ground at night and then burrow close to the surface during the day. Soil dwelling earthworms live and feed in the soil, rather than at the surface. Vertically burrowing earthworms engage in what is known as casting, which is when they ingest soil and extract nutrients from plant litter and other organic matter, emerge from their burrows, and deposit their waste on the surface in small mounds. Researchers found that after the application of glyphosate, the casting activity of vertically burrowing earthworms essentially ceased. Cast mound mass also decreased by 46%. In contrast, casting activity of this species remained constant when there was no application of glyphosate. In the second species, the soil dwelling earthworms, reproduction decreased by 56% after glyphosate application.
As a secondary effect of glyphosate applications, there is an immediate increase of available nitrate and phosphate in the soil. The researchers believe this is due to mass plant die-offs. Plants normally take in these nutrients and, as they die off, the study confirms that there are more nutrients available in the soil. These pulses of nutrient availability can lead to increased leaching and surface runoff into groundwater systems or nearby waterways. These excess nutrients lead to an increase in algal growth on the surface of waterways. These algal blooms block sunlight from reaching plants that are far from the surface, causing them to die. As these plants die, oxygen is depleted from the water, creating what is known as a “dead zone” where other organisms can no longer survive.
Other studies have demonstrated the detrimental effects that a wide range of pesticides can have on earthworms and other soil biota. One study on worms found 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. In 2014, researchers also found that earthworms exposed to fungicides in conventionally farmed soil are at a stark disadvantage to worms in land managed organically. Earthworms exposed to the fungicide epoxiconazole are able to detoxify the chemical, but gain half as much weight as worms from an organic farm, where their population is also 2 to 3 times higher.
Soil biota 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 the 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.
One way to protect soil biota, other wildlife, and the ecosystem as a whole from the harmful effects of pesticides is to support organic agriculture over conventional, chemical-intensive farming. Beyond Pesticides supports organic agriculture as effecting good land stewardship. The pesticide reform movement, citing pesticide problems associated with chemical agriculture, from groundwater contamination and runoff to drift, views organic as the solution to this serious environmental threat. It is impossible to discuss the ecological benefits of organic agriculture without discussing the devastating effects of conventional agriculture.
Conventional agriculture relies on toxic pesticides that contaminate air, water, soil, and living things, such as the earthworms mentioned in the studies cited above; organic agriculture does not allow the use of toxic pesticides. Chemical-intensive agriculture relies on synthetic chemical fertilizers that reduce soil organic matter and contaminate waterways; organic agriculture does not permit the use of synthetic fertilizers and relies instead on nutrient sources that tend to be less soluble and more stable in the soil, because of the expectation that healthy soil will produce microbes that can make the nutrients naturally available over a longer period of time.
To learn more about these impacts on wildlife (which includes soil biota), visit Beyond Pesticides’ Wildlife Page, where we discuss how organic systems save wildlife from the dangerous impacts of pesticides, encourages them to flourish, and restores the natural balance that is unable to exist in chemical-intensive agriculture.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.