Glyphosate (N-phosphonomethylglycine), the active ingredient in the herbicide Roundup that is manufactured by Monsanto is the most popular herbicide in use today in the United States, and increasingly throughout the World. Americans spray an estimated 180-185 million pounds of the weed killer, on their yards and farms every year. All the acute toxicity tests have found that glyphosate is nearly nontoxic to mammals; however, there have been for some time a minority of scientists and experts who believes that glyphosate may be much more toxic than is claimed and push for studying potential impacts to human health from low level constant exposure to glyphosate. This past year glyphosate was labeled a probable carcinogen by the International Agency for Research on Cancer, IARC, which is the cancer research arm of the World Health Organization.
Now, a new research study recently republished in Nature magazine has found that glyphosate impacts the life of soil dwelling organisms, the soil itself and our water resources. The study directly links the effect of glyphosate-based herbicides on two common species of earthworms that play an important role in the life of soil and ecology, breaking down dead organic matter.
Earthworms are nature’s farmers breaking down the dead organic matter and incorporating the organic matter into the soil by their burrowing and casting (releasing their feces in the soil). Earthworms living in soils (or your compost bin) decompose organic matter. Decomposition releases nutrients locked up in dead plants and animals and makes them available for use by living plants. Earthworms do this by eating organic matter and breaking it down into smaller pieces allowing bacteria and fungi to feed on it and release the nutrients. So when you impact earthworms you impact the life of the soil, the health of our plants and ecosystem.
In this greenhouse based study the scientists directly linked the effect of earthworms on different plant species and the effect of glyphosate-based herbicides on earthworms and their ecosystem functions. The scientists had initially assumed that glyphosate would stimulate earthworm activity and reproduction due to increased availability of food and thus increase soil nutrient availability, water infiltration and decomposition. However, they found exactly the opposite.
The activity and reproduction of earthworms was dramatically decreased by glyphosate-based herbicides. Surface cast production of the anecic earthworm species almost ceased after the herbicide was applied and reproduction of both earthworm species was substantially decreased. Taken together, the effect of glyphosate and earthworm activity on soil ecosystem services, the increased availability of nitrate and phosphate after herbicide application poses the danger of leaching these nutrients into groundwater systems and aquatic ecosystems. Reduced earthworm populations in areas with pesticide contamination decreases water infiltration and can cause higher surface runoffs heavy rains.
Earthworms represent the major part of the animal biomass in soil and influence plant growth and health both directly by changes of root growth and indirectly by changing the physical, chemical, or biological soil environment. The life of soil is the life of mankind. Earthworms are essential to soil health and the side-effects of glyphosate and other herbicides on earthworms, should be further studied and more seriously considered in farming practices.
If you would like to learn more about the study, the full text can be accessed here.
Gaupp-Berghausen, M. et.al. Glyphosate-based herbicides reduce the activity and reproduction of earthworms and leads to increased soil nutrient concentrations. Sci Rep 5, 12886-doi 10 1038/srep 12886 (2015).