I was handed my first bottle of herbicide in my senior year of college, during an invasive shrub removal on the University of Georgia’s campus in Athens. I had taken part in invasive plant removals for years, both throughout Athens and in my hometown in Wisconsin, but all of those removals had been done by hand, with painstaking hours spent pulling up seedlings, cutting vines off trees, and chopping down shrubs. At this removal, we were applying glyphosate (the active ingredient in Roundup) to the stumps of the shrubs we were cutting down in an attempt to fully kill them in one go.
As I held the bottle of glyphosate — stained blue so that we could see where it was sprayed — a flurry of thoughts raced through my brain: “I’m here to help the environment — don’t herbicides cause harm? Is this going to hurt native plants? Where will the glyphosate end up, and what other organisms will it affect? What happens if this gets on my skin? Will I get cancer from this?”
Though I was concerned and conflicted, the reason for glyphosate was clear: Without herbicides, any work we did that day would be useless. We were removing heavenly bamboo (Nandina domestica), an invasive shrub commonly used in landscaping whose berries are poisonous to native birds. The roots were too dense to dig up, so we cut the plant down as close to the ground as possible. But, as with many other invasive plants, the stump and root-sprouting ability of Nadina meant that leaves would reappear within a year. By using herbicides, we could prevent the Nandina from resprouting and increase the chance of actually killing it.
The more I work with invasive plants, both as a scientist and an avid participant in removal efforts, the more I understand why I was handed that bottle of glyphosate. Invasive plants wreak havoc on ecosystems by outcompeting native species, often forming dense stands of nothing but the invader. This leads to a reduction in native plants and the other native organisms that depend on them. Learning about herbicides has convinced me that although my initial concerns were valid, herbicides currently offer the best hope we have to control invasive plants.
Herbicides need not be used in all situations: Some plants are effectively controlled through mowing, burning, or the use of natural pests. In small areas, hand pulling plants can be enough for local eradication, though this takes dedication. (I’m on year three of yanking Chinese privet regrowth in my backyard.) But in most cases, these other options aren’t effective or the invasive plant covers too much land to be controlled by labor-intensive methods. When an invasive plant grows over multiple acres — as I’ve seen with my study subject, cogongrass — herbicide application can be done by one person in mere hours, compared with the days it would take people to pull plants by hand. Using herbicides drastically reduces the amount of people and time needed to manage invasive plants, increasing our chance of making a meaningful dent in existing populations.
The more I work with invasive plants, both as a scientist and an avid participant in removal efforts, the more I understand why I was handed that bottle of glyphosate.
The level of herbicides used to control invasive plants is usually not enough to impact people living nearby, according to the Environmental Protection Agency, but managers applying herbicides can be exposed to much higher levels and are thus at higher risk for acute and chronic illness. If I had gotten glyphosate on my skin, it could have caused some irritation but likely would not have had any long-term effects. (Accidental ingestion, though, could have been more serious.) In regards to cancer, the EPA describes glyphosate as “not likely to be carcinogenic to humans,” but the International Agency for Research on Cancer reached the opposite conclusion and lists it as “probably carcinogenic to humans.” Some studies have linked glyphosate to an increased risk of various cancers, with a 2021 meta-analysis concluding that there is compelling evidence that glyphosate-based herbicides cause non-Hodgkins lymphoma. (The author of that study disclosed that he had been a paid expert in glyphosate litigation.)
Herbicides don’t have a much better track record environmentally. In the same way that invasive plants choke out any competitors, many herbicides indiscriminately kill whatever plants they touch. The effects of herbicides can also spread beyond plants themselves, affecting microorganisms and animals. Landscapes created by herbicides and invasive plants are visually opposite but face the same problem: The brown fields of plants killed by herbicides and the vibrant green fields of densely growing invasive plants both lack biodiversity.
This dichotomy puts people dedicated to protecting their local biodiversity in an impossible spot: Do they risk their own health and that of their local ecosystem to effectively control invasive plants using herbicides, or do they let invasive plants smother the native organisms they hold dear? Many managers feel the same way I do; we don’t want to use them, but we feel that there aren’t better options. Even after herbicides are used, invasive plants still dominate many landscapes. Without herbicides, we will be admitting defeat, and invasive plants will spread unchecked far beyond their current boundaries.
Although herbicides are currently our best tool in this fight, we cannot and should not rely on them forever. Some invasive plants have already developed resistance, which renders current herbicides useless against them and will likely render them useless against more plants in the future. We could develop new herbicides, but they would likely continue to create issues for both human and environmental health.
The solution to the problems caused by herbicides is not to turn a blind eye to the issues they cause, but to develop better solutions for invasive plant management — ideally, new management methods that are targeted at a few or single species, are safer for humans, and have a lower environmental impact. Research is currently being done to create control methods that target only one species (methods such as biological control, RNAi, and autotoxicity), which would allow us to kill only the invasive plants while leaving other organisms, including humans, unharmed.
It takes more work to develop a species-specific management method for every invasive plant than it does to create one indiscriminately killing herbicide. But I believe that this is the most sustainable way for us to manage invasive plants while causing the least harm. I hope for a day when we won’t need to use herbicides, but until then I’ll use my glyphosate sparingly.
UPDATE: This piece has been updated to note that the author of a 2021 meta-analysis that concluded that there is compelling evidence that glyphosate-based herbicides cause non-Hodgkins lymphoma has been a paid expert in glyphosate litigation.
Elizabeth Esser is a Ph.D. student at Mississippi State University whose research focuses on invasive plant management. She was part of the Fall 2024 cohort of the Young Voices of Science program.