Renewable Farming

New study: How glyphosate impacts earthworms

Several years ago at a Farmland Foundation reception in Washington DC, I met an EPA official in charge of pesticide registration. 

He exuded confidence that his agency was protecting the U.S. public from toxins, while permitting scientific advances in crop protection.

I asked, “Does EPA require toxicological studies of herbicide effects on soil organisms such as earthworms, bacteria and fungi?”

He looked a little puzzled. “We ask for toxicity studies based on lab animals — primarily rats and rabbits, as proxies for the effects on humans.”

Thus it’s not surprising that there’s little published data on herbicide effects on the soil food web.

One of those studies — analyzing the effect of glyphosate on earthworms — was just released August 5 by the Institute of Zoology at the University of Natural Resources and Life Sciences in Vienna, Austria. (Note that it’s not a U.S.-sponsored study coming from an American land grant college.)

Some of the findings:

1. Analytical data on understanding the effect of glyphosate on earthworms is still “very scarce.”

2. Three weeks after glyphosate application, “surface casting activity of vertically burrowing earthworms (Lumbricus terrestris) almost ceased three weeks after herbicide application.

3. Reproduction of soil-dwelling species (Aporrectodea caliginosa) was reduced by 56% three months after herbicide application.

These results were contrary to the researchers’ expectations. They had theorized that earthworm activity would increase due to the extra availability of residue from weeds killed by the glyphosate. The report is very well-written, with excellent background data on the benefits of earthworms in production agriculture.

You can download and read the full study, released August 5, as a PDF — just click this link.