MIKE MILLER
I heard a new term the other day that piqued my curiosity: Chemical Trespass. The context was in a seminar being given by Prairie Rivers Network concerning herbicide damage to non-target species. For the last decade, there has been increasing evidence that many pesticides are doing their thing outside of where they were applied, hence their effects are “trespassing” into areas where they aren’t welcome.
The evidence of herbicide trespass is most visible in deformed or curled leaves on trees and other plants in natural areas. Last summer, I visited Nature Preserves throughout the state. In almost every natural area, I saw evidence of the chemical trespass even in areas where herbicides were not being applied within a mile of the site.
How could this be?
To answer that question, we need some background. Pesticides (herbicides, fungicides, insecticides, etc.) have been in use for a long time, but in the last decade of the 20th century, their use grew exponentially. In the early 1990s, soy beans were engineered to be resistant to a broad spectrum chemical herbicide known as glyphosate. This made it much easier to grow soybeans. You can easily kill the weeds and keep the beans. Corn crops were also benefiting from herbicides such as atrazine and 2,4-D, which kill the weeds not the corn. A new herbicide known as Dicamba became widely used in agriculture around 2016. The engineering of crops that are designed to be planted in partnership with a specific herbicide has been the biggest factor in the increased use of pesticides. The United States Geological Survey estimates that more than one billion pounds of pesticides are used each year in the United States. However, pesticides are not only used in agriculture. The lawncare, maintenance of utility and transportation rights-of-ways, and recreation groundskeeping all contribute to chemical trespass.
In Illinois, there are more than 27 million acres of land (75% of the landscape) in conventional row-crop agriculture. The Illinois Department of Agriculture is the agency charged with ensuring the proper use, licensing, and enforcement of pesticide regulations in the state. Anyone using a pesticide in a commercial industry or on public lands must go through training and pass some rigorous testing.
They also investigate complaints from people experiencing pesticide damage in non-target areas. From 2017 through 2019 they received a huge increase of complaints. Most of those complaints weren’t from people seeing damage in natural areas. It was from farmers seeing damage to their crops. Remember that new herbicide (Dicamba) I mentioned earlier? Many farmers were still planting (and treating) glyphosate resistant soy beans but their neighbors moved on to Dicamba resistant soy beans. It turns out that Dicamba is much more of a volatile chemical and the herbicide can escape a field by vapor even several days after application. Now, farmers using Dicamba must go through increased training on ways of reducing vapor drift. As added insurance, most farmers plant bean varieties that are resistant to both herbicides. Unfortunately, nature isn’t quite as adaptable and native plants and trees aren’t genetically altering themselves to resist the witches brew that is released upon the environment each year.
Recently, Prairie Rivers Network, an independent affiliate of the National Wildlife Federation completed a six-year study on the effects of herbicide drift in a report to the Illinois Nature Preserves Commission. Here’s a link to the DNR report
The study found that there were 99 species of trees, 48 species of shrubs and vines, and 115 species of herbaceous plants that were growing in our state-protected nature preserves that were showing signs of impact by herbicides. They also sent many samples to the lab to test for trace chemicals, and 99.9989% of those samples came back positive for herbicides (most commonly Dicamba and 2,4-D). It’s disheartening to know that even though these areas are protected, they still suffer ecological harm.
While the levels of exposure that these plants are receiving are small compared to a lethal dose at ground zero, they still are impacted. Plants impacted by vapor drift have reduced flower production which decreases pollinator visitation and impacts nutritional seed production. We are making our habitats sick and that impacts far more than the plants. It is also important to note that the study didn’t just focus on nature preserves in rural areas. It was also in unban preserves, where we also live. We also don’t really know the long-term effects of low-dose exposure on these trees and plants. We don’t know how many years an ancient oak can withstand having its leaf growth impacted before it dies.
To find out more about herbicide drift, and what you can do to report non-target impacts, Visit Prairie Rivers Networks resource page