Integrative Pest Management
The idea of avoiding pesticides when controlling plant pests is called, “Integrative Pest Management,” or “IPM” for short. The best practice is to first consider other methods such as biological, cultural, or physical tactics before resorting to chemical applications.
A cultural practice would be selecting native plants evolved to your region’s soils, climate, and fauna. Another practice would be mulching with woodchips to reduce weed germination and feed fungal food webs that favor native plants. A cultural-physical practice would be to densely plant the “weed vacuum” (bare soil) with evergreen plants (groundcovers, shrubs, and trees) to shade out weed re-invasions and reduce winter stormwater runoff.
Caring environmentalists who have tried every organic trick in the books have concluded that eradicating certain invasive species requires herbicide, and that neglecting invasive monocultures is far more damaging to ecosystems. Consider streamside knotweed with 10-ft deep roots that can’t be manually uprooted without eroding streambanks and damaging salmon nests, that can’t be allowed to spread because it severely degrades the native plant food sources that feed the bugs that feed salmon fingerlings. Weed cloth has been tried for decades, but the manufacture and transport of large rolls has its own environmental footprint, and it simply doesn't work. Knotweed only regrows, erodes streambanks, and spreads downstream at high rates. To save salmon, the reluctant conclusion is that chemical treatment with the safest effective herbicide is a necessity. These trials and errors evolve to become "best practices" applied by practitioners trained in safe handling and careful herbicide applications, who take measures to avoid off-target damage to native plants and pollinators. Best practices are thoroughly reviewed with scientific analysis and oversight, carefully navigating environmental and health risks.
Many homeowner-stewards become discouraged with manual methods that often don't work or make infestations worse. Herbicide applications may be an effective option to reduce erosion, combined with mulching and replanting of natives species. But, landowners must assume responsibility for applications on their property only, including effects to neighboring properties, and carefully consider the health-risk and environmental-cost trade-offs of chemical vs. manual removal methods. Do-it-yourselfers must first be confident with both identifying invasive plants and taking measures to preserve native plants, and to properly use PPE (gloves, eye pro, long pants and sleeves, or other recommendations per the label) before applying herbicide products. Avoid rain, and follow seasonal effectiveness listed in the Invasive Weed Calendar Guidelines. It is legally required for licensed applicators and consumers to read and follow the label.
If not, licensed herbicide professionals may be found at: https://agr.wa.gov/services/licenses-permits-and-certificates/pesticide-license-and-recertification/pesticide-and-spi-licensing/license-search. Most restoration professionals have weighed the risks of herbicide vs. the risks of invasive neglect, and choose to judiciously apply herbicide in the appropriate season for the reasons below.
The rationale for herbicide
The main reason for using herbicide is that it reduces soil erosion. Cut & treat or stem injections retain treated roots in the ground to slowly decay, holding soil and building soil structure for the benefit of establishing native plants. Herbicide can affect soil microbes, but it's generally considered short-term and minor compared to manual methods that remove wood in the ground and erode topsoil that takes centuries to build. Erosion reduces the forest's soil sponge, a hedge against drought stress, floods, and wildfire risk. Loss of rotting roots in the ground also reduces fungal filtration of toxic stormwater runoff. Stormwater is rain runoff from roads, roofs, and lawns, tainted with oil, air pollution and unnecessary fertilizers and pesticides. Stormwater is considered the "number one polluter of Puget Sound" that can overwhelm combined-sewer systems (CSO's), dumping raw sewage into public waters. Considerable air pollution is deposited, sequestered, and partially neutralized in healthy soil, so any soil disturbance can carry dissolved toxins into water bodies where "bio-accumulation" concentrates toxins up the food chain, in salmon, orcas, and people who eat salmon.
"Slow, insidious soil erosion threatens human health," and is considered one of "the biggest environmental problems the world faces" and is closely linked to the "erosion of civilizations" (https://news.cornell.edu/stories/2006/03/slow-insidious-soil-erosion-threatens-human-health-and-welfare); (https://academic.oup.com/bioscience/article/58/4/363/310371). Many industrial farmers, having lost untold volumes of topsoil, are now practicing "no-till" farming methods to preserve soil health.
For restoration professionals, herbicide is a key tool on erosion-prone slopes and for many species for which manual methods disturb soil and simply don't work: root fragments only grow back, creating thickets all the more difficult to control. Repeated pruning over many years may eventually starve invasive plants on small private lots, but public land managers dealing with exponentially spreading invasives on large acreages cannot justify transporting crews or volunteers with polluting vehicles to "organically" and ineffectively control invasive plants using methods that are more harmful to the environment. Vehicle fuel is acutely more toxic and used in far greater quantities than herbicide. Given limited budgets, the magnitude of the invasive problem and re-invasion rates, efficacy is imperative.
Minimizing the quantity of pesticides in our environment requires nipping invasive plants in the bud before they become monocultures region-wide.
Industrial farmers have repeatedly proven that monocultural crops attract pests as a result of losing biodiversity with its natural checks and balances (https://phys.org/news/2020-11-diversity-pesticide.html). Due to the rate of invasive spread and the fact introduced invasives have no natural checks, herbicides are necessary to prevent monocultural conditions that would likely require employing worse rodenticides and insecticides in the future. Skilled applicators also apply herbicide in the right season, minimizing the quantities of products used. It's very important to read product labels carefully and/or hire qualified professionals guided by this application calendar.
Restoration professionals mostly use products with the active ingredients glyphosate, triclopyr, and imazapyr as directed by government agencies who have analyzed the health and environmental effects of various herbicides. Professional products often are "aquatic" restricted-use formulations that are only available to licensed professionals, that are usually 50% active ingredient - the concentration used for cut&dab treatments. Aquatic herbicides are deemed safe for fish and amphibians, necessary for use around wetlands or riparian zones, but concentrated herbicides are considered more risky to human health (although less than many risks we overlook daily - see below), and are therefore only available to licensed applicators trained for safe use. Licensed applicators have a short list of aquatic surfactants vetted by the Dept. of Ecology (see calendar link in above paragraph) to assist the absorption of herbicide into the leaf when spraying. Professionals carefully dilute concentrated herbicides and surfactants to approximately 2% active ingredient (a.i.) for foliar sprays. Ready-to-spray consumer formulations are usually pre-mixed at 2% a.i. with surfactants that are not necessarily fish-safe, therefore they are not permitted for use around streams or wetlands. It's particularly important to avoid spraying consumer products unless you have one dry day followed by two forecasted dry days.
Pesticide-pollinator concerns
Skilled restoration practitioners are able to avoid directly spraying pollinators, but this does not prevent chemical exposure through systemic uptake of herbicides throughout the plant, where nectar may contain trace amounts of herbicide.
This systemic uptake may play a role in pollinator decline, and given the quantity of glyphosate used in repeat agricultural applications, it could be a serious concern. However, forestry applications use 1 - 2% of herbicides used in agriculture, and for restoration, herbicides are intended to preserve native plant diversity necessary to sustain insects and pollinators. There may be evolving science, but the INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY concluded that“glyphosate has low toxicity for bees and earthworms."
Based on recent news reports, this is likely not true for "neonic" insecticides (neonicotinoids) used in farming and the ornamental flower industry, but I have not reviewed the scientific literature on this subject.
Insecticides also kill beneficial insects, far beyond the target pests. Insecticides often get confused with herbicides, both of which are technically "pesticides."
"Pesticide is a broad term that includes insecticides, herbicides (weed or plant killers), fungicides, rodenticides, miticides (mite control), molluscicides (for snails and slugs), and other materials like growth regulators or antimicrobial products such as bleach and sanitary wipes that kill bacteria." (http://ipm.ucanr.edu/PMG/PESTNOTES/warning.html)
Some chemical-herbicide alternatives (concentrated vinegar) may change soil pH, risk irreversible eye damage, and just "burn down" tops of weeds guaranteeing the need for repeat applications. Vinegar herbicides are acutely toxic to bees and pollinators and can burn, even permanently blind the applicator. For homeowners wanting familiarity, vinegar may be a preferred method for weeds in sidewalk cracks around the home. For safety, wear proper PPE (gloves and eye protection!) and other precautions on the label of natural pesticides. Some recommend mowing invasives as an alternative to herbicide, but gas-powered mowing emits air pollution more carcinogenic than glyphosate (see studies cited below) and routinely kills pollinators - 70% of which are ground nesting. Mowing may spread weed seeds and not kill invasive roots. Glyphosate is usually limited to the target plants, and "drift" can be tracked by yellowing leaves on affected plants (one week delayed effect), whereas air pollution from mowing is actually ingested by all people downwind, and CO2 remains in the atmosphere for centuries.
Again, insecticides are very different than herbicides, and it's important to analyze the properties of all chemicals, natural or otherwise. Restoration is different than farming, where herbicides in restoration control invasive monocultures in order to preserve native plant biodiversity necessary to sustain pollinators. Invasive species are the second leading cause of species extinctions behind the number one cause, habitat destruction (such as paving and clearing for development, infilling wetlands, and high-intensity wildfires). Invasive plants degrade habitat and "are listed as a driver for more than half of the extinctions in each of the vertebrate taxa analysed" (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4780541/). Invasive infestations reduce resilience to disturbance (disease, insect pests, fire) and alter vital functions such as tree regeneration, forest structure and hydrology.
Risk Assessments for Human Health
The International Agency for Research on Cancer (IARC), an arm of the World Health Organization (WHO), recently published an often-cited analysis of over 1,000 independent studies on glyphosate, the active ingredient in Roundup, the most heavily use herbicide in the world. An academic review of the WHO report can be found at: http://blogs.oregonstate.edu/mgcoordinators/2018/10/15/glyphosphate-questions-answers/
In short, the review explains that the IARC listed glyphosate as "a probable human carcinogen." This surprised many governmental agencies tasked with protecting public and environmental health. The IARC responded and clarified their listing as identification of "potential hazards," quite different than actual risk assessments.
The IARC placed glyphosate in the "probable" Group 2 A list of potential carcinogens, a category that includes: 1) Red meat, 2) Indoor emissions from burning wood, 3) Emissions from high-temperature frying, 4) Late-night work shifts.
Group 2A is less risk than the Group 1 category of "known carcinogens" which include, but are not limited to: 1) Processed meats, 2) All alcoholic beverages, 3) Sunlight, 4) Engine exhaust (diesel), 5) Benzene (in gasoline), 6) Outdoor air pollution.
For many compounds, the "dose makes the poison" (aspirin, some vitamins, many natural remedies), and studies employ high concentration doses. While many governments are banning glyphosate due to public fear, their scientific agencies find over-the-counter dilutions of glyphosate or food residues “unlikely to cause cancer in humans." These scientific arms of governments with robust research resources include:
For ecologists who understand the health risks of losing bird populations and native pollinator habitat region-wide (from loss of plant diversity due to aggressive invasive plant spread), the risks of glyphosate exposures are far less worrisome. The probability of Non-Hodkins lymphoma (NHL) to ag workers is 2.8% compared to 2% for the general public, not a statistically significant difference, but boosting glyphosate to the "probable" 2A category.
Perhaps the risks to farmers, ag workers, and restoration practitioners who handle concentrated formulations is greater than the risks to the general population, so professionals are highly advised to wear PPE and aim for zero exposure.
Still, farmers generally live longer than the average citizen, despite their above-average exposure to diesel exhaust and sunlight, both carcinogens in higher risk categories than glyphosate (https://www.ncbi.nlm.nih.gov/pubmed/29136183 and https://www.epa.gov/sites/production/files/2016-09/documents/glyphosate_issue_paper_evaluation_of_carcincogenic_potential.pdf). There is evidence that risks to ag workers may be due to fertilizer exposures, not necessarily glyphosate (https://cancercommun.biomedcentral.com/articles/10.1186/s40880-017-0225-4). One science-writer describes glyphosate risks as "negligible," comparable to "the risk of just being alive" (https://sciencebasedmedicine.org/update-on-glyphosate/).
There appears to be growing research about glyphosate potentially affecting gut microbiomes, a contributing factor to many western diseases. In addition, glyphosate is known to have mineral-binding capacity that chemically "adheres" to soil particles (a reason farmers often use glyphosate due to its low risk to groundwater). It's reported that some farmers spray glyphosate on food crops to dessicate tops of root vegetables (for easier harvest), with likely translocation of chemicals to food. It's unknown to this author whether glyphosate residues on food could bind up minerals in the body (such as calcium in bones), or how much glyphosate "demineralizes" soil and therefore nutrient content of food. Concerned consumers might be advised to buy organic food, or better, grow your own organic food (be sure to conduct soil tests) to minimize dependency on carbon-based transport of industrially-produced farm products.
However, our food system and farming practices are not the focus of this website. We are explaining the tradeoffs of herbicide used for invasive control in order to preserve topsoil and biodiversity. We are not defending or opposing farming practices, only suggesting that farmers consider expanding their native plant diversity in hedgerows - even if establishing quality pollinator habitat requires initial herbicide applications.
What if...
The opinions shared in this practitioner perspective come from environmentalists who actually do the work, and we also want to know the risks or "relative worry" of products that government agencies direct us to use. We accept the herbicide risks, which are considered low by a vast majority of scientists, because we understand the risks of runaway invasives are a clear and future danger. However, this begs the question: “What if someone downstream or one of our fellow practitioners gets cancer?”
Tragically, many people get cancer from many different causes, sometimes genetic or from impossible-to-pinpoint exposures to hundreds of toxins, many natural and many man-made, that may or may not be listed in the IARC report. When cancer strikes, blame is often directed toward a conditioned prejudice, or "lightning rod."
Tragically close to home, the web designer of this very website lost his battle with cancer. He was an employee and a restoration practitioner who didn’t for a moment think his herbicide work was to blame, because he contracted cancer well before starting his career. Plus he did his research, earning a Masters of Science degree from the UW School of Environment and Forestry Sciences. He was proud of this website legacy, helping to explain the eco-logic behind herbicide, necessary to reduce erosion and preserve native plant diversity required by the birds he loved. And he was comforted that all the trees he planted made a lasting contribution to the world, and co-workers continue to plant and spread the seeds of his favorite madrones.
Ironically, the tragedy of cancer helps explain the predicament of invasive species, because invasives are themselves an ecological cancer. With many invasive species spreading region-wide, it's more accurate to describe it as a cancerous epidemic, one that is spreading by seed rain. Ecological cancers can shut down vital functions like natural regeneration of native trees, like pollinator habitat needed for our food supply, or predispose forests to fire, or create conditions for insect and disease outbreaks, a fact monocultural farms and feedlots have proven again and again. In essence, when invasive species are the second leading cause of species extinctions, when cancer threatens human life, survival sometimes requires chemical therapy.
For some species, like ivy, their uncontrolled growth is relentless, spreading in slow-motion. For others, like holly, their spread is epidemic, at a near-exponential rates. Cancerous epidemics illustrated by invasive plants show how epidemics operate: one property gets infested and then infests neighboring properties and so on. This unfortunate reality forces our appeal. We ask that the public consider tolerating the necessity of chemical therapies.
Yes, glyphosate has become a ‘wedge issue’ that divides rural, environmental, and progressive concerns. We should really be working together to limit unnecessary and reckless use of all products, commensurate with science-assessed risks, all the while figuring out better farming and forestry practices that preserve our soil, food & wood supply, salmon, and a stable climate.
"Fear sells," and it is my hope that passionate, caring people can temper their emotional view of threats in the world and not let slanted media hype blind us to greater risks. Notwithstanding valid concerns, misinformed fear can divert attention and resources away from more pressing issues, and fear itself can be a factor in disease.
Lastly, the longer we wait, the more expensive it will be. Neglect is not an option - we are approaching a tipping point when invasive plant infestations will soon be ungettable.
Thank you (!) citizen-volunteers who steward their land, or any permitted land. There is SO much work to be done. Steve Richmond, June 2021
The idea of avoiding pesticides when controlling plant pests is called, “Integrative Pest Management,” or “IPM” for short. The best practice is to first consider other methods such as biological, cultural, or physical tactics before resorting to chemical applications.
A cultural practice would be selecting native plants evolved to your region’s soils, climate, and fauna. Another practice would be mulching with woodchips to reduce weed germination and feed fungal food webs that favor native plants. A cultural-physical practice would be to densely plant the “weed vacuum” (bare soil) with evergreen plants (groundcovers, shrubs, and trees) to shade out weed re-invasions and reduce winter stormwater runoff.
Caring environmentalists who have tried every organic trick in the books have concluded that eradicating certain invasive species requires herbicide, and that neglecting invasive monocultures is far more damaging to ecosystems. Consider streamside knotweed with 10-ft deep roots that can’t be manually uprooted without eroding streambanks and damaging salmon nests, that can’t be allowed to spread because it severely degrades the native plant food sources that feed the bugs that feed salmon fingerlings. Weed cloth has been tried for decades, but the manufacture and transport of large rolls has its own environmental footprint, and it simply doesn't work. Knotweed only regrows, erodes streambanks, and spreads downstream at high rates. To save salmon, the reluctant conclusion is that chemical treatment with the safest effective herbicide is a necessity. These trials and errors evolve to become "best practices" applied by practitioners trained in safe handling and careful herbicide applications, who take measures to avoid off-target damage to native plants and pollinators. Best practices are thoroughly reviewed with scientific analysis and oversight, carefully navigating environmental and health risks.
Many homeowner-stewards become discouraged with manual methods that often don't work or make infestations worse. Herbicide applications may be an effective option to reduce erosion, combined with mulching and replanting of natives species. But, landowners must assume responsibility for applications on their property only, including effects to neighboring properties, and carefully consider the health-risk and environmental-cost trade-offs of chemical vs. manual removal methods. Do-it-yourselfers must first be confident with both identifying invasive plants and taking measures to preserve native plants, and to properly use PPE (gloves, eye pro, long pants and sleeves, or other recommendations per the label) before applying herbicide products. Avoid rain, and follow seasonal effectiveness listed in the Invasive Weed Calendar Guidelines. It is legally required for licensed applicators and consumers to read and follow the label.
If not, licensed herbicide professionals may be found at: https://agr.wa.gov/services/licenses-permits-and-certificates/pesticide-license-and-recertification/pesticide-and-spi-licensing/license-search. Most restoration professionals have weighed the risks of herbicide vs. the risks of invasive neglect, and choose to judiciously apply herbicide in the appropriate season for the reasons below.
The rationale for herbicide
The main reason for using herbicide is that it reduces soil erosion. Cut & treat or stem injections retain treated roots in the ground to slowly decay, holding soil and building soil structure for the benefit of establishing native plants. Herbicide can affect soil microbes, but it's generally considered short-term and minor compared to manual methods that remove wood in the ground and erode topsoil that takes centuries to build. Erosion reduces the forest's soil sponge, a hedge against drought stress, floods, and wildfire risk. Loss of rotting roots in the ground also reduces fungal filtration of toxic stormwater runoff. Stormwater is rain runoff from roads, roofs, and lawns, tainted with oil, air pollution and unnecessary fertilizers and pesticides. Stormwater is considered the "number one polluter of Puget Sound" that can overwhelm combined-sewer systems (CSO's), dumping raw sewage into public waters. Considerable air pollution is deposited, sequestered, and partially neutralized in healthy soil, so any soil disturbance can carry dissolved toxins into water bodies where "bio-accumulation" concentrates toxins up the food chain, in salmon, orcas, and people who eat salmon.
"Slow, insidious soil erosion threatens human health," and is considered one of "the biggest environmental problems the world faces" and is closely linked to the "erosion of civilizations" (https://news.cornell.edu/stories/2006/03/slow-insidious-soil-erosion-threatens-human-health-and-welfare); (https://academic.oup.com/bioscience/article/58/4/363/310371). Many industrial farmers, having lost untold volumes of topsoil, are now practicing "no-till" farming methods to preserve soil health.
For restoration professionals, herbicide is a key tool on erosion-prone slopes and for many species for which manual methods disturb soil and simply don't work: root fragments only grow back, creating thickets all the more difficult to control. Repeated pruning over many years may eventually starve invasive plants on small private lots, but public land managers dealing with exponentially spreading invasives on large acreages cannot justify transporting crews or volunteers with polluting vehicles to "organically" and ineffectively control invasive plants using methods that are more harmful to the environment. Vehicle fuel is acutely more toxic and used in far greater quantities than herbicide. Given limited budgets, the magnitude of the invasive problem and re-invasion rates, efficacy is imperative.
Minimizing the quantity of pesticides in our environment requires nipping invasive plants in the bud before they become monocultures region-wide.
Industrial farmers have repeatedly proven that monocultural crops attract pests as a result of losing biodiversity with its natural checks and balances (https://phys.org/news/2020-11-diversity-pesticide.html). Due to the rate of invasive spread and the fact introduced invasives have no natural checks, herbicides are necessary to prevent monocultural conditions that would likely require employing worse rodenticides and insecticides in the future. Skilled applicators also apply herbicide in the right season, minimizing the quantities of products used. It's very important to read product labels carefully and/or hire qualified professionals guided by this application calendar.
Restoration professionals mostly use products with the active ingredients glyphosate, triclopyr, and imazapyr as directed by government agencies who have analyzed the health and environmental effects of various herbicides. Professional products often are "aquatic" restricted-use formulations that are only available to licensed professionals, that are usually 50% active ingredient - the concentration used for cut&dab treatments. Aquatic herbicides are deemed safe for fish and amphibians, necessary for use around wetlands or riparian zones, but concentrated herbicides are considered more risky to human health (although less than many risks we overlook daily - see below), and are therefore only available to licensed applicators trained for safe use. Licensed applicators have a short list of aquatic surfactants vetted by the Dept. of Ecology (see calendar link in above paragraph) to assist the absorption of herbicide into the leaf when spraying. Professionals carefully dilute concentrated herbicides and surfactants to approximately 2% active ingredient (a.i.) for foliar sprays. Ready-to-spray consumer formulations are usually pre-mixed at 2% a.i. with surfactants that are not necessarily fish-safe, therefore they are not permitted for use around streams or wetlands. It's particularly important to avoid spraying consumer products unless you have one dry day followed by two forecasted dry days.
Pesticide-pollinator concerns
Skilled restoration practitioners are able to avoid directly spraying pollinators, but this does not prevent chemical exposure through systemic uptake of herbicides throughout the plant, where nectar may contain trace amounts of herbicide.
This systemic uptake may play a role in pollinator decline, and given the quantity of glyphosate used in repeat agricultural applications, it could be a serious concern. However, forestry applications use 1 - 2% of herbicides used in agriculture, and for restoration, herbicides are intended to preserve native plant diversity necessary to sustain insects and pollinators. There may be evolving science, but the INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY concluded that“glyphosate has low toxicity for bees and earthworms."
Based on recent news reports, this is likely not true for "neonic" insecticides (neonicotinoids) used in farming and the ornamental flower industry, but I have not reviewed the scientific literature on this subject.
Insecticides also kill beneficial insects, far beyond the target pests. Insecticides often get confused with herbicides, both of which are technically "pesticides."
"Pesticide is a broad term that includes insecticides, herbicides (weed or plant killers), fungicides, rodenticides, miticides (mite control), molluscicides (for snails and slugs), and other materials like growth regulators or antimicrobial products such as bleach and sanitary wipes that kill bacteria." (http://ipm.ucanr.edu/PMG/PESTNOTES/warning.html)
Some chemical-herbicide alternatives (concentrated vinegar) may change soil pH, risk irreversible eye damage, and just "burn down" tops of weeds guaranteeing the need for repeat applications. Vinegar herbicides are acutely toxic to bees and pollinators and can burn, even permanently blind the applicator. For homeowners wanting familiarity, vinegar may be a preferred method for weeds in sidewalk cracks around the home. For safety, wear proper PPE (gloves and eye protection!) and other precautions on the label of natural pesticides. Some recommend mowing invasives as an alternative to herbicide, but gas-powered mowing emits air pollution more carcinogenic than glyphosate (see studies cited below) and routinely kills pollinators - 70% of which are ground nesting. Mowing may spread weed seeds and not kill invasive roots. Glyphosate is usually limited to the target plants, and "drift" can be tracked by yellowing leaves on affected plants (one week delayed effect), whereas air pollution from mowing is actually ingested by all people downwind, and CO2 remains in the atmosphere for centuries.
Again, insecticides are very different than herbicides, and it's important to analyze the properties of all chemicals, natural or otherwise. Restoration is different than farming, where herbicides in restoration control invasive monocultures in order to preserve native plant biodiversity necessary to sustain pollinators. Invasive species are the second leading cause of species extinctions behind the number one cause, habitat destruction (such as paving and clearing for development, infilling wetlands, and high-intensity wildfires). Invasive plants degrade habitat and "are listed as a driver for more than half of the extinctions in each of the vertebrate taxa analysed" (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4780541/). Invasive infestations reduce resilience to disturbance (disease, insect pests, fire) and alter vital functions such as tree regeneration, forest structure and hydrology.
Risk Assessments for Human Health
The International Agency for Research on Cancer (IARC), an arm of the World Health Organization (WHO), recently published an often-cited analysis of over 1,000 independent studies on glyphosate, the active ingredient in Roundup, the most heavily use herbicide in the world. An academic review of the WHO report can be found at: http://blogs.oregonstate.edu/mgcoordinators/2018/10/15/glyphosphate-questions-answers/
In short, the review explains that the IARC listed glyphosate as "a probable human carcinogen." This surprised many governmental agencies tasked with protecting public and environmental health. The IARC responded and clarified their listing as identification of "potential hazards," quite different than actual risk assessments.
The IARC placed glyphosate in the "probable" Group 2 A list of potential carcinogens, a category that includes: 1) Red meat, 2) Indoor emissions from burning wood, 3) Emissions from high-temperature frying, 4) Late-night work shifts.
Group 2A is less risk than the Group 1 category of "known carcinogens" which include, but are not limited to: 1) Processed meats, 2) All alcoholic beverages, 3) Sunlight, 4) Engine exhaust (diesel), 5) Benzene (in gasoline), 6) Outdoor air pollution.
For many compounds, the "dose makes the poison" (aspirin, some vitamins, many natural remedies), and studies employ high concentration doses. While many governments are banning glyphosate due to public fear, their scientific agencies find over-the-counter dilutions of glyphosate or food residues “unlikely to cause cancer in humans." These scientific arms of governments with robust research resources include:
- US Environmental Protection Agency, December 18, 2018
- European Food Safety Authority, November 12, 2015
- Australian Pesticides and Veterinary Medicine Authority, March 15, 2017
- New Zealand Environmental Protection Authority, August 2016
- Health Canada, April 2015
For ecologists who understand the health risks of losing bird populations and native pollinator habitat region-wide (from loss of plant diversity due to aggressive invasive plant spread), the risks of glyphosate exposures are far less worrisome. The probability of Non-Hodkins lymphoma (NHL) to ag workers is 2.8% compared to 2% for the general public, not a statistically significant difference, but boosting glyphosate to the "probable" 2A category.
Perhaps the risks to farmers, ag workers, and restoration practitioners who handle concentrated formulations is greater than the risks to the general population, so professionals are highly advised to wear PPE and aim for zero exposure.
Still, farmers generally live longer than the average citizen, despite their above-average exposure to diesel exhaust and sunlight, both carcinogens in higher risk categories than glyphosate (https://www.ncbi.nlm.nih.gov/pubmed/29136183 and https://www.epa.gov/sites/production/files/2016-09/documents/glyphosate_issue_paper_evaluation_of_carcincogenic_potential.pdf). There is evidence that risks to ag workers may be due to fertilizer exposures, not necessarily glyphosate (https://cancercommun.biomedcentral.com/articles/10.1186/s40880-017-0225-4). One science-writer describes glyphosate risks as "negligible," comparable to "the risk of just being alive" (https://sciencebasedmedicine.org/update-on-glyphosate/).
There appears to be growing research about glyphosate potentially affecting gut microbiomes, a contributing factor to many western diseases. In addition, glyphosate is known to have mineral-binding capacity that chemically "adheres" to soil particles (a reason farmers often use glyphosate due to its low risk to groundwater). It's reported that some farmers spray glyphosate on food crops to dessicate tops of root vegetables (for easier harvest), with likely translocation of chemicals to food. It's unknown to this author whether glyphosate residues on food could bind up minerals in the body (such as calcium in bones), or how much glyphosate "demineralizes" soil and therefore nutrient content of food. Concerned consumers might be advised to buy organic food, or better, grow your own organic food (be sure to conduct soil tests) to minimize dependency on carbon-based transport of industrially-produced farm products.
However, our food system and farming practices are not the focus of this website. We are explaining the tradeoffs of herbicide used for invasive control in order to preserve topsoil and biodiversity. We are not defending or opposing farming practices, only suggesting that farmers consider expanding their native plant diversity in hedgerows - even if establishing quality pollinator habitat requires initial herbicide applications.
What if...
The opinions shared in this practitioner perspective come from environmentalists who actually do the work, and we also want to know the risks or "relative worry" of products that government agencies direct us to use. We accept the herbicide risks, which are considered low by a vast majority of scientists, because we understand the risks of runaway invasives are a clear and future danger. However, this begs the question: “What if someone downstream or one of our fellow practitioners gets cancer?”
Tragically, many people get cancer from many different causes, sometimes genetic or from impossible-to-pinpoint exposures to hundreds of toxins, many natural and many man-made, that may or may not be listed in the IARC report. When cancer strikes, blame is often directed toward a conditioned prejudice, or "lightning rod."
Tragically close to home, the web designer of this very website lost his battle with cancer. He was an employee and a restoration practitioner who didn’t for a moment think his herbicide work was to blame, because he contracted cancer well before starting his career. Plus he did his research, earning a Masters of Science degree from the UW School of Environment and Forestry Sciences. He was proud of this website legacy, helping to explain the eco-logic behind herbicide, necessary to reduce erosion and preserve native plant diversity required by the birds he loved. And he was comforted that all the trees he planted made a lasting contribution to the world, and co-workers continue to plant and spread the seeds of his favorite madrones.
Ironically, the tragedy of cancer helps explain the predicament of invasive species, because invasives are themselves an ecological cancer. With many invasive species spreading region-wide, it's more accurate to describe it as a cancerous epidemic, one that is spreading by seed rain. Ecological cancers can shut down vital functions like natural regeneration of native trees, like pollinator habitat needed for our food supply, or predispose forests to fire, or create conditions for insect and disease outbreaks, a fact monocultural farms and feedlots have proven again and again. In essence, when invasive species are the second leading cause of species extinctions, when cancer threatens human life, survival sometimes requires chemical therapy.
For some species, like ivy, their uncontrolled growth is relentless, spreading in slow-motion. For others, like holly, their spread is epidemic, at a near-exponential rates. Cancerous epidemics illustrated by invasive plants show how epidemics operate: one property gets infested and then infests neighboring properties and so on. This unfortunate reality forces our appeal. We ask that the public consider tolerating the necessity of chemical therapies.
Yes, glyphosate has become a ‘wedge issue’ that divides rural, environmental, and progressive concerns. We should really be working together to limit unnecessary and reckless use of all products, commensurate with science-assessed risks, all the while figuring out better farming and forestry practices that preserve our soil, food & wood supply, salmon, and a stable climate.
"Fear sells," and it is my hope that passionate, caring people can temper their emotional view of threats in the world and not let slanted media hype blind us to greater risks. Notwithstanding valid concerns, misinformed fear can divert attention and resources away from more pressing issues, and fear itself can be a factor in disease.
Lastly, the longer we wait, the more expensive it will be. Neglect is not an option - we are approaching a tipping point when invasive plant infestations will soon be ungettable.
Thank you (!) citizen-volunteers who steward their land, or any permitted land. There is SO much work to be done. Steve Richmond, June 2021