For decades, commercial agriculture has used chemical herbicides as the preferred method for weed control. As knowledge about their negative environmental impacts has grown, non-sustainable herbicides have become considered a necessary evil in commercial agriculture because weed proliferation can reduce production by 20-50 %, depending on conditions.1
Image Credit: Dusan Petkovic/Shutterstock.com
These herbicides are fast-acting, effective, and economical to use. However, many chemical herbicides have significant environmental impacts, including negative health effects on non-target organisms and impacts on human health. Overuse of these herbicides has also led to the emergence of herbicide-resistant weeds.
The environmental impacts of herbicides are well-documented, and efforts are underway to mitigate them. As the global agriculture grapples with potentially using less herbicides, there is increased focus on alternative methods, such as more targeted formulations of herbicides, biobased herbicides, and sustainable weed management practices.
The Environmental Impacts of Herbicides
Research has shown that the level of herbicide toxicity in an environment depends on several factors related to the chemical composition of herbicides, meteorological conditions, application techniques, volume used, soil conditions, and biotic qualities of organisms in the environment.2
Persistent herbicides are a particularly significant concern. These chemicals break down slowly and remain in the soil long after their intended use. The repeated application of these herbicides only exacerbates their persistence and environmental impacts.
In general, the environmental impacts include those on non-target organisms, humans, and herbicide resistance of targeted plants.
Non-Target Organisms
Glyphosate herbicides are among the most commonly used herbicides and the most impactful. When present in concentrations higher than 10 mg/L, glyphosates harm earthworms, lowering their reproduction rates and damaging their DNA.3
Research has also shown that high concentrations of glyphosates in the environment adversely impact bees, which are critical for pollinating cultivated and wild flowering plants.4
In addition to directly impacting targeted and non-targeted organisms, herbicides also indirectly impact habitats adjacent to agricultural fields.
Research shows that birds living in these adjacent habitats must cope with lower food sources, such as insects and grains. As a result, the number of bird species living next to agricultural areas often decreases.5
Frequent use of herbicides can also result in these chemicals leaching into groundwater. This can harm non-target organisms that consume this water and those living in nearby aquatic environments.
Herbicide Effects on Humans
Significant exposure to herbicides can cause adverse health effects in humans. One study found glyphosate herbicides can cause damage to the liver, kidneys, and endocrine system. These herbicides have also been found to cause neurodegenerative disorders, and prenatal exposure has been linked to increased risk of autism spectrum disorders.6
Paraquat is a particularly toxic herbicide to humans, causing vomiting, nausea, diarrhea, and fluid loss in concentrations higher than 30 mg/kg. Acute exposure can seriously damage internal organs and the nervous system, potentially leading to death.
Unfortunately, herbicides often enter our food system. One study focused on the pre-harvest application of Roundup fertilizer. It found levels of glyphosate residues that were higher than the acceptable levels set by the Canadian government.7
Increased Herbicide Resistance
Weed resistance to herbicides is growing worldwide.1 This has more of an indirect environmental impact because of the implications for industrial agriculture and the continued use of herbicides.
For many years, companies have used genetically modified herbicide-resistant crops so that farmers could spray these proprietary crops with herbicides indiscriminately. This prolonged and indiscriminate application of herbicides has led to the emergence of herbicide resistance in some weeds.
Researchers have found more than 350 weed biotypes resistant to one or more herbicides. While that is a relatively small number, repeated use of a single herbicide is known to select for resistant strains.8
Emerging Solutions and Future Outlook
Stakeholders have largely acknowledged that the status quo is unacceptable, and the industry has shifted its approach to herbicides.
One significant change has been a move toward pre-emergence herbicides. These chemicals are applied to agricultural soil before crop seedlings emerge to specifically target weed seeds and seedlings. This approach has been proven more effective compared to post-emergence herbicides. Using pre-emergence herbicides also leads to better targeting of weeds, lowering impacts on crops and non-target organisms.9
There is also increased interest in solutions that involve natural and eco-friendly alternatives. One such approach involves the use of benign crop cultivars that crowd out weeds.
Another approach uses natural enemies of weeds, such as insects, animals, and biological pathogens. For example, certain strains of bacteria and fungi appear to be very promising for weed suppression. One recent study focused on allelochemicals released by tomato plants that suppress weed germination.10
The study results of these emerging methods are mixed, but authors routinely voice optimism that one or more sustainable herbicide methods will emerge and ideally replace non-sustainable herbicides.
Click here to download a PDF copy of this page
References and Further Reading
- Parven, A. et al. (2024 June 19). Herbicides in modern sustainable agriculture: environmental fate, ecological implications, and human health concerns. International Journal of Environmental Science and Technology Vol 22: 1181–1202. https://link.springer.com/article/10.1007/s13762-024-05818-y
- Fingler S. et al. (2017). Herbicide micropollutants in surface, ground and drinking waters within and near the area of Zagreb, Croatia. Environmental Science and Pollution Research Vol. 24: 11017–11030. https://link.springer.com/article/10.1007/s11356-016-7074-6
- Gill J. et al. (2017 December 14) Glyphosate toxicity for animals. Environmental Chemical Letters Vol. 16: 401–426. https://link.springer.com/article/10.1007/s10311-017-0689-0
- Belsky J. et al. (2020 July 27). Effects of fungicide and herbicide chemical exposure on Apis and non-Apis bees in agricultural landscape. Frontiers in Environmental Science Vol. 8: 81. https://www.frontiersin.org/journals/environmental-science/articles/10.3389/fenvs.2020.00081/full
- Boatman N. et al. (2004 November 16). Evidence for the indirect effects of pesticides on farmland birds. International Journal of Avian Science Vol. 146:131–143. https://onlinelibrary.wiley.com/doi/full/10.1111/j.1474-919X.2004.00347.x
- Rawat D. et al. (2023 July). Hazardous impacts of glyphosate on human and environment health: Occurrence and detection in food. Chemosphere Vol. 329: 138676. https://www.sciencedirect.com/science/article/pii/S0045653523009438#sec5
- Xu J. et al. (2019 December). Glyphosate contamination in grains and foods: an overview. Food Control 106:106710. https://link.springer.com/article/10.1007/s13762-024-05818-y#ref-CR189
- Campbell, J. et al. (2023). Herbicide-Resistant Weeds and Their Management. Oregon State University Extension Service. https://extension.oregonstate.edu/catalog/pub/pnw-437-herbicide-resistant-weeds-their-management
- Cioni F. et al. (2011 January 26). Weed control in sugarbeet. Sugar Tech Vol 12: 243–255. https://link.springer.com/article/10.1007/s12355-010-0036-2
- Raza, T. et al. (2025 April 17). Bioherbicides: revolutionizing weed management for sustainable agriculture in the era of One-health. Current Research in Microbial Sciences Vol 8: 100394. https://www.sciencedirect.com/science/article/pii/S2666517425000562#sec0006
Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.