10
Jul
Public Rejects Pesticides to Manage “Invasive” Species, Study Finds
(Beyond Pesticides, July 10, 2025) A study in People and Nature, with the goal of better understanding the social acceptability of introduced species management (ISM), often labeled “invasive species,” in the U.S., “conducted an online experiment with vignettes describing hypothetical but realistic ISM scenarios, varying targeted taxon (insect or plant), control method (mechanical, chemical and biological), risk severity (low and high) and type of non-target risk (to humans or native species).” This study highlights the debate on defining “invasive” species, as well as the low levels of acceptability by the general public for chemical controls such as pesticides.
In addition, as pesticide hazards increase, the authors note that the responses show acceptance for only mechanical controls that incorporate manual removal of species, such as through pulling, cutting, clipping, or mowing. “Surprisingly, there was no significant difference in how respondents ranked risks to people and risks to native species,” the researchers report. This shows the values placed on both human health and biodiversity and “highlight[s] the need for evidence-guided ISM, which includes evidence of harmful impacts of introduced species, as well as risks and benefits of management activities, as one potential way to increase the social acceptability of non-native species management.”
In supporting the organic movement as an alternative to chemical-intensive land management, the study notes that: “Concerns about non-target risks of chemicals are widespread as evidence of detrimental effects on species, food webs and human health continues to accumulate. Modern pesticides now widely used in ISM are promoted as more selective and less toxic than older versions, but this may be misguided.” (See research here, here, here, and here.)
The authors continue by saying: “[E]ven with repeated efforts, chemicals are often insufficient for managing widespread introduced species. Our respondents show a general aversion to these treatments, a continued trend of social discomfort towards this method which first coalesced in U.S. environmentalism of the 1960s following the publication of Rachel Carson’s Silent Spring. The withdrawal of many products no longer deemed safe for humans or the environment and documentation of widespread negative impacts to wildlife and human health may explain our respondent’s aversion towards chemical treatments.” (See studies here and here.)
As Beyond Pesticides advocates, current risk assessments do not adequately capture the harm to all organisms and the environment. There is a wide body of scientific literature connecting the use of petrochemical pesticides and synthetic fertilizers, typically used in the management of many “invasive” species, to detrimental effects on human health, biodiversity, and the environment. The failure to fully consider these adverse effects in the registration process, advocates say, violates the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). (See more on regulatory deficiencies here and here.)
In previous Beyond Pesticides coverage, the topic of what constitutes “invasive” species is discussed. As shared on the Ecological Management of Problem Vegetation (“Invasive Weeds”) page, the landscape in the U.S. and around the world has vastly changed over the last few decades. The replacement of diverse ecosystems with monocultures and development projects has been accompanied by disturbances that create new habitats. As people have moved around, they have carried with them — sometimes unwittingly, sometimes purposefully — plants and animals from their former homes. When the habitat suits the new plant or animal, it happily makes itself at home.
When these new inhabitants interfere with what humans want to do, the unwanted species are identified as “pests” or “weeds.” There are some weeds that seem to be especially difficult to manage—particularly those that have become established in “natural” or managed ecosystems. Are these species “invasive” or are they opportunists taking advantage of disturbed ecosystems? This is the ever-evolving debate over “invasive” versus introduced species and emphasizes how important definitions are.
Many scientists have different opinions on this matter. While stressing the importance of preventing the introduction of unwanted species, David Pimentel, PhD, argued at one point that alien weeds pose serious problems for agricultural and natural ecosystems, although most of his work pointed to the true agricultural costs of pesticides from secondary pests and lost ecosystem services. Virginia Daley and Fritzi Cohen argued that humans have always assisted the spread of plants wherever they have moved, and that the current concern about “invasive plants” is an excuse to mount chemical warfare campaigns. (See more Beyond Pesticides coverage on “invasives” here, here, here, and here.) Despite the framing of the definition of “invasives,” toxic chemicals are not an answer, but in fact, pose greater threats than the problems they are meant to solve.
The current study in People and Nature describes the definition of introduced species by stating: “Human-assisted biological invasions occur when species are transported (accidentally or purposefully) from their current range to a new environment where they are not native. This process unfolds in stages and species need to overcome multiple environmental and ecological filters. Most of the non-native species that arrive in a new environment actually fail to establish, and of those that initially establish and grow, many fail to naturalize, that is, create self-sustaining, reproducing populations. Of those that naturalize, some thrive and expand their range from initial introduction areas, and they may become abundant in local ecosystems. Those non-native species that naturalize and become harmful by affecting native species, ecosystems, human well-being or the economy are considered ‘invasive,’ but the distinction between introduced and ‘invasive’ species has become blurred and scientists disagree on terminology.”
The researchers note that perceptions of “invasive” species, and of the language used to characterize non-native species, can greatly vary in both the scientific community and by the general public. “Part of the complexity that makes biological invasions a wicked problem is the enormous variation in introduced taxa (from microbes, to insects, to plants, to birds, to fish, to mammals, etc.) and their ecological niches (decomposers, herbivores, parasites, diseases, predators, etc.), causing a wide variation of potential and realized impacts,” the authors say. They continue, “Impacts can vary according to how different stakeholders are affected and through time, reflecting a mix of scientific evidence and value judgements and creating intense disagreements about which non-native species should be managed and how.” (See studies here, here, here, and here.)
The intent of ISM is to avert or reduce harmful impacts of non-native species, usually by preventing introductions in the first place, but when utilized after a species is well established “reflects a belief that the non-native species is causing harm, and that risks associated with management are smaller compared to risks of not managing.” This approach is problematic, as the authors point out that “for the vast majority of non-native species we have extremely limited or no published evidence for their ecological impacts. Even for well-studied species, documented impacts can range from negative, to neutral, to beneficial.” (See scientific literature here, here, here, here, and here.)
To better understand public opinion and acceptability of ISM, the researchers conduct an experiment with 24 “realistic but hypothetical ISM scenarios varying targeted taxon (insect or plant), control method (mechanical, chemical and biological), risk severity (low and high) and non-target risk (to human well-being or native species)” involving non-native plants and insects. The experimental scripts include written descriptions in short, plain language regarding invasion scenarios and proposed management actions to measure how acceptable courses of action are perceived to be.
The scenarios incorporate responses on a “7-point bipolar Likert scale ranging from ‘strongly disagree’ through ‘neither agree nor disagree’ to ‘strongly agree’ with an additional option of ‘I do not know’” to assess acceptability. As a result, the authors note: “Comparing within non-target impacts, acceptability was always significantly lower for biological and chemical relative to mechanical control, regardless of taxon targeted. Acceptability is only separated for biological and chemical controls in comparison to mechanical control across non-target impacts. When biocontrol targeted plants and involved risks to human well-being, acceptability was significantly lower than mechanical control of either plants or insects with risks to native species.”
These results highlight a preference for mechanical controls of introduced and non-native species. In summary, the researchers say: “Our findings suggest that many current ISM practices have limited acceptability by the U.S. public, even when risk levels are low… [W]e found that concerns of management potentially harming native species were equally strong as impacts affecting human well-being. Our results point to a greater societal concern for the fate of native species than generally acknowledged and may be consistent with evidence showing a shift from utilitarian value orientation to more ecocentric or mutualistic views of nature and wildlife in the U.S. affecting attitudes regarding management of non-native species.”
Aside from the vast amount of research highlighting the negative effects of chemical control methods, Beyond Pesticides has also covered scientific evidence on biological control. Studies (see here, here, and here) demonstrate that biological control has successfully managed non-native fire ants and the tree of heaven (Ailanthus altissima), and can be considered a less-toxic option. Mechanical control, however, remains the safest alternative and is proven effective in managing species considered “invasive” or unwanted.
In particular, goats can be used as a mechanical method to organically manage land. As stated in previous Daily News articles, goat grazing has been demonstrated to be an effective tool because the herd eats unwanted vegetation and then cycles nutrients back into the soil, thus fertilizing. Goats get a drink and deliver water to dry sites one pint at a time, thus irrigating, and also aerating, mulching, and tilling soils with their hooves. (See additional coverage on goats here, here, here, here, and here.)
To learn more about organic land management and non-toxic lawns and landscapes, see here and here. The holistic, systems-based approach of organic offers both health and environmental benefits while managing non-native species in a way that promotes ecosystem health and mitigates myriad adverse effects that are documented with chemical-intensive methods. Sign up to receive Action of the Week and Weekly News Updates delivered right to your inbox to stay informed and engaged.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source:
Simmons, W. et al. (2025) Common approaches to introduced species management face widespread acceptance problems in the United States, People and Nature. Available at: https://besjournals.onlinelibrary.wiley.com/doi/am-pdf/10.1002/pan3.70053.
