The Bureau of Land Management (BLM) is increasingly opting for pesticides to control weeds and invasive grasses like cheatgrass on public lands. Cheatgrass accelerates wildfire risk and outcompetes the native plants that are essential to maintaining healthy ecosystems.
But our public lands are a national treasure, and any use of pesticides on them must be carefully weighed against the many risks they pose to human health, soil health, native biodiversity, wildlife, and aquatic ecosystems. Alternative control strategies are often equally, or even more, effective in the long run.
BLM manages a vast swath—245 million acres—of some of the most beautiful and important conservation areas in the country. Much of BLM land is in the west, from the San Pedro Riparian National Conservation Area, a critical habitat for animals and migratory birds in southern Arizona; to the alpine tundra, sage brush steppe, and canyons of Colorado’s western slope; to Bears Ears National Monument, with its deep religious and cultural significance to Native American tribes in Utah; to Idaho’s geological wonder, Craters of the Moon National Monument.
These public lands support native flora and fauna and healthy, thriving ecosystems. Using pesticides on them could harm the insects, birds, and other animals that inhabit them. Many pollinator species, such as bees, rely on public lands for their survival. These pollinators support ecosystems by fertilizing plants, and if their populations decline because of pesticide exposure, entire food chains could be disrupted. Herbicides, which are a type of pesticide designed to control plants, may also harm native plants that insects and other animals depend on for food, while polluting waterways and harming aquatic life.
At a minimum, pesticides should never be used on public lands that are designated as National Conservation Areas. These areas provide critical habitat and migration corridors for wildlife and are designated to prioritize natural and cultural resource conservation over traditional multiple uses, such as energy development, livestock grazing, recreation, hunting and fishing, and timber harvesting.
The problem with Indaziflam
Take Indaziflam. It is one of seven herbicides recently approved by the U.S. Environmental Protection Agency (EPA) for treatment of weeds in rangelands and forests by public agencies. Indaziflam, sold under the brand name Rejuvra, is what’s known as a pre-emergent herbicide, or a chemical used to prevent weeds before they sprout by preventing the seeds from germinating. Developed by Bayer, Indaziflam is now being considered for large-scale application across millions of acres of BLM and U.S. Forest Service land to control cheatgrass and other invasive annual grasses that increase wildfire risk.
Rejuvra being sprayed by a helicopter on county public lands in Colorado. Note the long plume and arial drift of the herbicide, spreading onto nearby homes and non-target plants and species. With run-off on the steep slopes, contaminated soils will send sediment downslope in local streams.
Such widespread use poses serious risks to human health, soil ecosystems, native biodiversity, and wildlife forage resources, says a growing body of scientific evidence. Emerging research, for instance, suggests that Indaziflam can damage DNA, which means it might be able to cause cancer at certain doses.
The herbicide has also been found to kill key protozoa in soil ecosystems that play a vital role in nutrient cycling and promoting plant growth. By killing those essential microbes, it may inadvertently foster conditions that favor soil-borne pathogens, while reducing plant growth and nutrient uptake, and essentially stripping soils of their fertility and resilience to climate change.
Indaziflam is non-selective, which means it not only kills invasive grasses, but also many native grasses and broad-leafed plants that are crucial for supporting pollinators, wildlife forage, and ecological recovery after wildfire, road building, and other disturbances on public lands. Because it acts by preventing seeds from germinating, the herbicide could be particularly harmful to federal native seed collection programs on public lands.
Indaziflam is touted as having a long-lasting residual effect — persisting in soil for up to three years. It is not intended for use near water bodies because of its high potential to run off into and contaminate surface waters, and harm fish, aquatic invertebrates, and aquatic plants.
Finally, it is worth noting that while cheatgrass is invasive, it also serves as a key forage resource for both domestic livestock and native wildlife such as elk and bighorn sheep. Eradicating cheatgrass without providing alternative forage could create a food gap, especially in late winter and early spring.
Any use of pesticides like Indaziflam on public lands must carefully consider these serious potential harms to human and ecological health. Spraying the herbicide near tribal lands, rural towns, and recreation sites, for example, is not advised given the emerging evidence of the chemical’s genotoxicity and its ability to linger in the environment for up to three years.
All recommendations on EPA’s directions on how to use the product must be followed carefully, such as not spraying near water bodies. But given the scale of proposed use of the herbicide across public lands, which often have streams, wetlands, or rivers coursing through them, and the chemical’s persistence in the environment, the potential for contaminating waterways during storm events is a serious concern.
Invasive grass management without pesticides
There are more ecologically sound approaches to managing invasive grasses. Manual or mechanical removal in combination with reseeding can be effective on smaller, high-priority restoration sites. Resting grazing allotments and reducing livestock on larger areas can prevent the spread of cheatgrass which flourishes on bare, open soil. Restoration planting with native broad-leaved plants and early successional plants can help re-establish competitive plant communities that naturally suppress cheatgrass over time.
Pesticide use is no golden ticket. Short-term eradication of weeds comes with long-term human and ecological health problems. Climate change and ever-shifting priorities on BLM lands will continue to disturb the land and foster the growth of invasive grasses like cheatgrass. We must develop effective strategies that work for the long term.
Chandra Rosenthal is the Director of PEER’s Rocky Mountain Office located in Denver, Colorado.
