A Cornerstone of Invasion Biology Crumbles

Over 20 years ago a study was published about the economic costs of introduced species. The study by David Pimentel et.al. (1) claimed that the economic costs of introduced species in the United States are $137 billion per year.   Despite many critiques of that study by academic scientists, the study remains a cornerstone of invasion biology and the “restoration” industry it spawned. 

The study has been cited by other academic scientists over 4,500 times and an update of the study published in 2005 has been cited over 5,800 times.  In addition to being influential with academic scientists, most media articles about “invasive species” begin with reference to that study and comments from native plant advocates on Conservation Sense and Nonsense often begin by quoting that study.  In other words, the bloated estimate of the economic costs of introduced species in the US is a powerful tool that continues to fuel attempts to eradicate non-native plants and animals in the US.  Therefore, a new study by Demetrio Boltovskoy et. al. (2) that critiques this estimate is of interest to us and we report that study to you today. 

The abstract of the new study (2) outlines the critique of Pimentel’s study by an international (Argentina, Canada, Switzerland, and US) team of scientists:

“The economic costs of non-indigenous species (NIS) are a key factor for the allocation of efforts and resources to eradicate or control baneful invasions. Their assessments are challenging, but most suffer from major flaws. Among the most important are the following:

  • the inclusion of actual damage costs together with various ancillary expenditures which may or may not be indicative of the real economic damage due to NIS;
  • the inclusion of the costs of unnecessary or counterproductive control initiatives;
  • the inclusion of controversial NIS-related costs whose economic impacts are questionable;
  • the assessment of the negative impacts only, ignoring the positive ones that most NIS have on the economy, either directly or through their ecosystem services. Such estimates necessarily arrive at negative and often highly inflated values, do not reflect the net damage and economic losses due to NIS, and can significantly misguide management and resource allocation decisions.”

The Pimental study misrepresents the economic impact of introduced plant and animal species in the US.  The most significant flaw in the evaluation of costs is that it does not take into consideration the benefits of introduced species.  Pimentel’s formula for evaluating economic impacts of introduced species is simplistic:

Losses & Damages + Control Costs = Total Costs

Source:  David Pimentel, et.al., “Environmental and Economic Costs of Nonindigenous Species in the United States” (1)

We need look no further than Pimentel’s study to see how the absence of economic benefits of introduced species in that equation distorts the evaluation of the economic impact of introduced species.  Pimentel has included the pests of agricultural crops and livestock in his calculation of total economic costs of $137 billion per year.  He calculates the cost of agricultural weeds, insect pests and pathogens as well as livestock diseases as $77.3 billion per year, which is 57% of his estimate of total costs of introduced species. 

In the same study, Pimentel says that 98% of the “US food system” are introduced species (corn, wheat, rice, cattle, and poultry) and he reported that the value of those products was $800 billion per year at the time of his study in 2000.  In other words, if the benefits of agricultural products had been included in Pimentel’s formula, the net benefit to the American economy of introduced species would be $663.4 billion per year ($800 billion of benefits – $136.6 billion of costs = $663.4 net benefit). (3) Similar calculations for most items on Pimentel’s hit list of introduced species would be required to accurately assess the economic costs of introduced species:

Purple loosestrife. GNU Free
  • The Boltovskoy study considers purple loosestrife an “innocuous species.” Studies have shown that purple loosestrife thrives where nutrient pollution feeds it and its presence reduces nutrient pollution, which is a benefit to the ecosystem in which it thrives.  Poisoning loosestrife to control it increases pollutants in the ecosystem.  Controlling the sources of nutrient pollution, such as leaky septic tanks and agricultural runoff, is the only long-term method to control purple loosestrife.
  • Millions of starlings are killed in the US every year because they eat crops, but they also eat insect predators of crops.  When the economic benefits of insect control by starlings are subtracted from the costs of crop predation, European countries choose not to kill starlings.
  • Zebra and Quagga mussels are on Pimentel’s list of troublemakers because they clog the water intake pipes of industrial, water, and power plants.  But there are substantial economic benefits of these mussels“these invasive bivalves significantly clarify the water of lentic waterbodies, which can mitigate phytoplankton blooms, including toxic Cyanobacteria…lessening the costs of [purifying drinking] water, and enhancing recreational activities…” (2) They are also a major source of food for waterfowl and have contributed to significant increases in waterfowl populations.  There are mechanical methods of preventing mussels from clogging water intake pipes.
  • Cats are often the target of eradication efforts, and they also appear on Pimentel’s list.  A fair assessment of the economic costs of cats should include their benefit as predators of rats and rabbits.  Cats are a non-toxic method of rodent control.  In their absence, rodenticides are used to kill rodents and rodenticides are known killers of birds.  Do rodenticides kill as many birds as cats?  Maybe. 
  • Many introduced plants are providing valuable food and habitat for animals, including native animals.  Eucalyptus that provide nectar during winter months, when little else is blooming, is essential to hummingbirds, bees, and other animals.  Eucalyptus are the also the winter homes of migrating monarch butterflies in California.  Yet, they are being destroyed by many public land managers because they are introduced.  Likewise, many berry-producing plants that are important food sources for birds and other animals are being eradicated by native plant advocates.
Monarchs roosting in eucalyptus, Pismo Beach, November 2021

Although the costs of control methods are included in Pimentel’s calculation of the economic costs of introduced species, the collateral damage of control methods are not.  Here are a few examples of the collateral costs associated with methods used to control introduced species.

Lanphere Dunes and Mad River Slough

In summary, a more accurate cost/benefit analysis of introduced species would look something like this:

(Losses & Damages + Control Costs) – Benefits – Damage of Control Methods = Total Cost or Benefit

In the absence of such an accurate assessment, scarce public resources will continue to be wasted on eradication projects that do more harm than good.  “Admittedly, [such an accurate assessment] requires much more knowledge of the effectives of nonindigenous species, yet it does not justify using [Pimentel’s] numbers for weighting the risks and harms involved, let alone using them for engaging in potentially feckless and wasteful eradication and control initiatives.” (2)

  1. David Pimentel, et.al., “Environmental and Economic Costs of Nonindigenous Species in the United States,” BioScience, January 2000
  2. Demetrio Boltovskoy, et.al., “Misleading estimates of economic impacts of biological invasions:  Including the costs but not the benefits,” Ambio, 2022
  3. It seems likely that Pimentel’s estimate of the value of agricultural products is the net value after costs of controlling agricultural pests are subtracted from gross value.  In other words, a more accurate calculation of the economic benefit of agricultural products in Pimentel’s formula is probably $800 billion + $77.3 billion (pest control costs). 

Conference of the California Invasive Plant Council: Fallacies and Failures

The California Invasive Plant Council held their 27th annual conference in Monterey in November.  It was their biggest conference, with about 400 attendees and more sponsors than ever before.  Clearly the industry that promotes the eradication of non-native plants is alive and well.  However, a closer look at the conference presentations suggests otherwise.  Eradication efforts are growing, but eradication success is not and establishing a native landscape after eradication is proving elusive.

A few common themes emerged from the presentations:

  • Eradication cannot be accomplished without using pesticides.
  • When eradication is achieved with pesticides, non-natives are rarely replaced by native plants.
  • Planting natives after non-natives are eradicated reduces re-invasion, but secondary invasions of different non-native plants are common.
  • “Managing” forests with prescribed burns did not result in more biodiversity than leaving the forest alone.

Goals of these eradication projects have shifted in response to these failures to achieve original goals:

  • Replacement plantings after eradication are sometimes a mix of natives and non-natives.
  • Inability to establish native grassland has given way to different goals.
  • Language used to describe the projects are evolving to be more appealing to potential volunteers.

Here are a few examples of presentations that illustrate these themes:

Eradicating beach grass in Point Reyes National Seashore

About 60% of sand dunes in the Point Reyes National Seashore were covered in European beach grass when the eradication effort began in 2000.  The goal of the project was to restore native dune plants and increase the population of endangered snowy plovers that nest on bare sand.

The project began by manually pulling beach grass from 30 acres of dunes at Abbott’s Lagoon.  The grass grew back within one year, presumably because the roots of the beach grass are about 10 feet long.  Manually pulling the grass from the surface does not destroy the roots.

A new method was devised that was more successful with respect to eradicating the beach grass.  The grass and its roots were plowed up by bulldozers and buried deep in the sand.  The cost of that method was prohibitively expensive at $25,000 to $30,000 per acre and the barren sand caused other problems.

The barren dunes were mobile in the wind.  Sand blew into adjacent ranches and residential areas, causing neighbors of the park to object to the project.  The sand also encroached into areas where there were native plants, burying them.  The bare sand was eventually colonized by “secondary invaders.”  Different non-native plants replaced the beach grass because they were more competitive than the desired native plants.

In 2011, the National Park Services adopted a third strategy for converting beach grass to native dune plants.  They sprayed the beach grass with a mixture of glyphosate and imazapyr.  At $2,500 to $3,000 per acre, this eradication method was significantly cheaper than the mechanical method.

However, it resulted in different problems that prevented the establishment of native dune plants.  The poisoned thatch of dead beach grass was a physical barrier to successful seed germination and establishment of a new landscape.  Where secondary invaders were capable of penetrating the dead thatch, the resulting vegetation does not resemble native dunes.

Presentation at California Invasive Plant Council conference regarding attempt to eradicate European beach grass at Point Reyes National Seashore

The concluding slides of this presentation were stunning.  They said it is a “Restoration fallacy that killing an invader will result in native vegetation.”  My 20 years of watching these futile efforts confirm this reality.  However, I never expected to hear that said by someone actually engaged in this effort.  The presenter mused that such projects are like Sisyphus trying to roll a boulder up hill. 

Presentation at California Invasive Plant Council conference regarding attempt to eradicate European beach grass at Point Reyes National Seashore

Attempting to plant Douglas fir after eradication of broom

Over a period of 5.5 years, broom was eradicated in plots in Oregon by spraying glyphosate.  The plots were then planted with Douglas fir seedlings that soon died.  They were replanted the following year and died in the second year.

There were two theories about why the plantings failed, both broadly described as “legacy” effects in the soil left by the broom.  One theory is that nitrogen levels were too high for successful growth of Douglas fir.  That theory is consistent with the fact that broom is a nitrogen fixer.  That is, broom—like all legumes—have the ability to transfer nitrogen in the atmosphere to nitrogen in the soil with the help of bacteria that facilitate that transfer.  Nitrogen generally benefits plant growth, but there can also be too much nitrogen.

The second theory is that Douglas fir requires a specific suite of mycorrhizal fungi for successful growth.  Mycorrhizal fungi live in roots of plants and trees.  They transfer moisture and nutrients from the soil to the plants.  Plants with a healthy suite of mycorrhizal fungi are more drought tolerant because they extract more moisture from the soil.

Neither of these theories has been successfully proven by this project.  They remain unanswered questions.  We were struck that the researchers had not considered the possibility that the repeated use of glyphosate could have been a factor in the failure of the Douglas fir.  Glyphosate is known to kill bacteria in the soil.  Could it also kill mycorrhizal fungi?  (We know that triclopyr kills mycorrhizal fungi.) That possibility was not considered by this project. Did the project consider that glyphosate also changes the consistency of the soil by binding certain minerals together?  It is more difficult for roots and water to penetrate the hard soil.  Were soil samples taken before and after repeated applications of glyphosate to determine how the soil had been changed by pesticide applications?

The published abstract for this project made this observation:  “It is typically assumed that once an invasive species is successfully removed, the impact of that species on the community is also eliminated.  However, invasive species may change the environment in ways that persist, as legacy effects, long after the species itself is gone.”  In fact, it seems likely that the pesticides used to eradicate the “invasive” species could also be the source of the “legacy effects.”

Does “managing” a forest result in greater biodiversity in the understory?

California State Parks tested that hypothesis by conducting prescribed burns in some of their forests in the Sierra Nevada 20 years ago, while leaving other portions of the forest “unmanaged.”

The abstract for this presentation describes the goals and expectations for the prescribed burns:  “Prescribed fire is a tool used to reduce fuels in the forests in the Sierra Nevada and mimic the low and moderate severity wildfires that burned before the onset of fire suppression.  A manager’s hope is that prescribed fire will create the disturbance necessary to stimulate the development of species rich understory communities and increase species richness, compared to unburned forests, which are often viewed as species depauperate.”

Twenty years after the burns, abundance and species composition of the understory in the burned areas were compared to the unburned areas.  They found little difference in the biodiversity of the understory of burned areas compared to unmanaged forests:

  • “Species richness was highly variable within burned and passively managed areas but was not statistically different.”
  • “Passively managed areas did not appear to be depauperate in understory species diversity compared to areas managed with prescribed fire.”
  • “Fire did not appear to reduce or enhance species richness numbers in burned areas, as compared to passively managed areas.”

No fires occurred in either the burned areas or the unmanaged areas during the 20-year period.  Therefore, this study did not test the theory that prescribed burning reduces fire hazards in forests.  This study found no significant differences in diversity of forest understory resulting from prescribed burns.

There are significant risks associated with prescribed burns.  They cause air pollution and they frequently escape the controlled perimeter of the fire, becoming wildfires that destroy far more than intended.  This study does not provide evidence that would justify taking those risks.  In fact, available evidence supports the “leave-it-alone” approach to land management.

Moving the goal posts

If at first you don’t succeed, you have the option of redefining success.  Here are a few of the projects presented at the conference that seemed to take that approach.

Make projects so small that success can be achieved

Eric Wrubel introduced himself as the National Park Service staff who is responsible for prioritizing invasive plants for removal in the National Parks in the Bay Area (GGNRA, PRNS, Muir Woods, and Pinnacles).  His work is based on the premise that the most successful eradications are those that are small.  The bigger the infestation, the greater the investment of time and resources it takes to eradicate it and the smaller the likelihood of success.  This is illustrated by a graph showing this inverse relationship between the size of the invasive population and the success of eradication.

Source: Rejmanek and Pitcairn, “When is eradication of an exotic pest plant a realistic goal?,” 2002

The process of prioritizing eradication projects began over 10 years ago with a survey of over 100 species of plants considered invasive.  Cal-IPC’s “watch list” was used to identify the plants that are not yet widely spread in California, but considered a potential problem in the future.  Cal-IPC’s risk assessment was the third element in the analysis.  Plants with “High” risk ratings by Cal-IPC were put higher on the priority list than those with “Moderate” or “Limited” ratings.  Plants that did not exist elsewhere in the region or watershed were also given higher priority, based on the assumption that re-invasion was less likely.

This is the list of eradication projects in the National Parks in the Bay Area that was presented at the conference of the California Invasive Plant Council. The projects marked with the red symbol for crossing out are completed projects. Nearly half of the plants on this hit list are not considered invasive in California.

The priority list showed that the highest priority eradication projects were quite small.  Some were just a few acres.  Buddleia jumped out as the 7th highest priority on only 13 acres.  Buddleia was recently added to a new category of plants on Cal-IPC’s “invasive” inventory.  It is not considered invasive in California, although it is considered invasive elsewhere.

In placing buddleia on its “hit list,” Cal-IPC illustrates one of the fundamental weaknesses of its evaluation method.  Cal-IPC does not evaluate pros and cons of non-native plants.  Only traits considered negative are taken into consideration.

Monarch sanctuary in Monterey, California. November 2018

Buddleia is one of the most useful nectar plants for pollinators in California.  We took the time to visit the monarch butterfly sanctuary in Monterey while attending the conference.  The monarchs are arriving now to begin their winter roost in the eucalyptus, Monterey pine and cypress in this small grove.  At the entrance to the sanctuary a sign instructs visitors to plant only native milkweed as the monarch’s host plant and only native flowers for nectar.  Fortunately whoever planted the flowering shrubs in the sanctuary didn’t follow the advice of the sign-makers.  They planted buddleia and other flowering non-natives such as bottle-brush.  Several species of butterflies and hummingbirds were enjoying those plants in the Sanctuary. Strict adherence to the native plant agenda is not beneficial to wildlife because animals do not share our prejudices.

Monarch nectaring on butterfly bush. butterflybush.com

Acknowledging the difficulties of converting non-native annual grass to native perennial grass

Pinnacles National Park acquired 2000 acres of former ranchland in 2006.  The park wanted to convert the non-native annual grasses and yellow-star thistle on the former ranch to perennial bunch grasses and oak woodland.  They were able to reduce the amount of yellow-star thistle by burning and spraying with herbicide, but cover of native species remained low.  Conversion of grasses from non-native annuals to native perennial grass has been tried many times, in many places, and for long periods of time.  These projects were notoriously unsuccessful.

The project at Pinnacles has changed its goal to plant forbs (herbaceous flower plants) instead of grasses and they report that they are having some success.   They justify that shift in goal on soil analysis that suggests forbs were more prevalent than perennial grasses in inland valleys in California than previously thought.

This change in goal could be described as “adaptive management,” which adjusts methods and goals in response to observable outcomes of existing methods.  You could also call it “trial and error.”  We would like to see more land managers make such adjustments to their strategies, rather than doing the same thing over and over again and expecting a different outcome.

Recruiting volunteers with appealing messages

There were several presentations about effective methods of recruiting volunteers to participate in restoration projects.  Some of their messages seem to acknowledge that the language used in the past may have alienated some potential volunteers.  Speaking from personal experience, I can confirm that observation.  Here are just a few of the cringe-worthy native plant mottos that I hope have been abandoned in favor of a more positive message:

  • “That plant doesn’t belong here.”
  • “That is a good plant and the other is a bad plant.”
  • “The invasive landscape is sick and requires chemotherapy.” (to justify the use of pesticides)
  • “That’s a trash bird.” (said of common, introduced birds, such as starlings and house sparrows)

The speaker advised those who work with volunteers to focus on why an unwanted plant is a problem rather than where it comes from.  Unfortunately, the list of problems is heavily influenced by the preferences of native plant advocates.  If their criticisms are not accurate, or they don’t acknowledge the advantages of the plant, little has been achieved by using euphemisms.  Here are a few of the inaccurate criticisms made of eucalyptus:

What was missing?

Ecological restoration is a major industry. Thousands of people are employed by the industry, which is funded by many different sources of public money.  Whether individual projects are successful or not, the industry will survive and thrive as long as it is funded.  Greater care should be taken to design and implement projects that will be successful.

Stepping back from the conference presentations of specific restoration projects, here are a few issues that were conspicuously absent from the conference. 

  • Pesticides are being widely used by the restoration industry. When projects don’t achieve desired outcomes, pesticides should be considered as a factor.  Did pesticides alter the soil?  Were beneficial microbes and fungi killed? How persistent was the pesticide in the soil?  How mobile was the pesticide in the soil?  Was pesticide applied in the right manner?  Could aerial drift account for death of non-target plants?  There are many other useful questions that could be asked.

Update:  The California Invasive Plant Council has published “Land Manager’s Guide to Developing an Invasive Plant Management Plan.”  It says very little about the disadvantages of using herbicides to eradicate plants they consider “invasive” other than a vague reference to “unintended consequences,” without discussion of what they are or how to avoid them. 

However, it does give us another clue about why eradication efforts are often unsuccessful. When herbicides are used repeatedly, as they have been in the past 20 years, weeds develop resistance to them:   “The International Survey of Herbicide Resistant Weeds (2018) reports there are currently 496 unique cases (species x site of action) of herbicide-resistant weeds globally, with 255 species…Further, weeds have evolved resistance to 23 of the 26 known herbicide sites of action and to 163 different herbicides.”  The Guide therefore recommends that land managers rotate herbicides so that the “invasive” plants do not develop resistance to any particular herbicide.  The Guide gives only generic advice to use “herbicide X” initially and “herbicide Y or Z” for subsequent applications.

In other words, the California Invasive Plant Council continues to promote the use of herbicides to kill plants they consider “invasive.”  They give advice about ensuring the effectiveness of herbicides, but they do not give advice about how to avoid damaging the soil, killing insects, and harming the health of the public and the workers who apply the herbicides.  May 20, 2019

  • Are workers who apply pesticides being adequately trained and supervised by certified applicators? The safety of workers should be one of many goals of restoration projects.
  • When non-native plants are eradicated, serious thought should be given in advance to the probable outcome. Will native plants return?  Will wildlife be harmed?  Will the risks of failure outweigh the potential benefits of success?
  • Is climate change taken into consideration when planning the replacement landscape? Are the plants that grew in the project location 200 years ago still adapted to that location?  Is there enough available water?
  • If new plantings require irrigation to be established, what is the water source? Is it recycled water with high salt content that will kill many plants, including redwoods?
  • Are the new plantings vulnerable to new infectious diseases, such as phytopthera or infestations of new insects such as shot-hole borer?
  • Does the project team have sufficient horticultural knowledge to choose plants that can survive in current conditions? Does the project team know the horticultural needs of the plants they are planting?  Is there enough sunlight, water and wind protection for the trees they are planting?

The public is investing heavily in the “restoration” of ecosystems.  We can only hope that our investment is being used wisely and that projects will not do more harm than good.  Cal-IPC can play a role in raising the questions that have the potential to improve projects and enable them to succeed.  The long-term survival of the “restoration” industry depends on it.

Most quotes are from abstracts of presentations published in the conference program.

Public reactions to conferences on invasive species are always illuminating

I am publishing a guest post by Jacques Tassin, who tells us of his personal experiences with presenting his findings about invasive species in public forums.  Jacques Tassin is a French ecologist. He has been working on invasive species for more than twenty years, especially on islands in the West Indian Ocean and Pacific Ocean.

Jacques Tassin

Dr.Tassin agreed to tell us about his interactions with the public because he believes the public’s views of invasive species are poorly understood and that improved understanding of the public’s views would improve communication about this controversial topic. 

I must add that my personal experiences with such interactions have revealed the same themes.  The public feels strongly that it is possible—even necessary—to control nature.  And much of that sentiment is based on guilt about the damage that humans have done to nature and a desire for redemption.  I prefer to respond to that viewpoint by informing the public of the damage being done in the name of “restoration.”  We cannot redeem ourselves by doing yet more damage.  However, I share Dr. Tassin’s frustration with scientists who are unwilling to speak to the public in ways that the public can comprehend.

Jacques Tassin is a new voice on Million Trees.  I am grateful for his participation in our discussion of invasion biology.

Million Trees

It takes much energy for a scientist to go down to the arena to meet the general public, for example in the form of a conference. But it is well worth it. On the one hand, because it allows scientists to hear a different kind of discourse than media coverage of the issue. On the other hand, because the comments and questions from the public are often very significant.

Following the publication of my book La Grande invasion: qui a peur des espèces invasives ? (The Great Invasion: Who Fears Invasive Species?) published in editions Odile Jacob in 2014, I was often invited to such meetings. I can distinguish several types of public reactions to my conferences.

The main one is the public’s seeming intolerance of the idea that we can agree to do nothing about the progression of an invasive species, even if it is proven that nothing can be done about it, or that the species in question does not have a clearly negative ecological or economic impact. Farmers and hunters are particularly opposed to this view of not intervening and therefore not controlling the environment. For these people, it is a question of putting nature in its place.

The public also strongly rejects the possibility that we cannot redeem our faults, or that we may not be able to undo what we have done, if we do not deal with invasive species. This reaction is the result of an activist stance that is particularly present in nature conservation associations. The remark that comes up most often is “we’re not going to sit back and watch.”

Finally, the third most frequent reaction is the belief that each invasive species introduced somewhere necessarily takes the place of another species. This principle of musical chairs seems deeply rooted in everyone’s mind. It is not certain that this is due to the theories of Robert MacArthur and E.O. Wilson’s about island biogeography. It seems much more likely that, deep in our imagination, the arrival of an intruder will end up with the departure of one of us.

In any case, it seems to me that the debate about invasion biology is far more concerned with social psychology than with the science of invasions. I am now certain that those who focus their discourse on the biological and ecological dimension of invasive species are headed in the wrong direction. Today, invasion biology is more in the field of psychology and beliefs than it is a question of a rational discourse. But it is clear that scientists are particularly ill-suited for this dialogue. Journalists who are used to talking to hundreds of thousands of listeners on the radio or in the press are much better equipped to do so. Scientists must learn from journalists how to communicate with the public about invasive species, whatever the public’s opinion of invasive species.

Jacques Tassin

Further Reading:

Tassin J., Thompson K., Carroll S.P., Thomas C.D. (2017). Determining whether the impacts of introduced species are negative cannot be based solely on science: a response to Russell and Blackburn. Trends in Ecology and Evolution, 32 (4) : 230-231.

Tassin, J. and C. Kull (2015). Facing the boader dimensions of biological invasions. Land Use Policy 42 : 165-169.

Tassin, J. (2014). La grande invasion. Qui a peur des espèces invasives ? Editions Odile Jacob. Paris, 216 p.

Beyond Pesticides: The voice of reason about pesticides

Beyond Pesticides logo

I attended my first Beyond Pesticides forum in 2014 in Portland, Oregon.  I have been a member of and donor to Beyond Pesticides ever since.  And I have purchased only organic food since attending that forum, because of a field trip to a community of farm workers that convinced me that growing our food without using pesticides benefits both consumers and producers of America’s food.  

In a recent letter to the National Invasive Species Council, Beyond Pesticides describes their organization and mission:

Founded in 1981 as a national, grassroots, membership organization that represents community-based organizations and a range of people seeking to bridge the interests of consumers, farmers and farmworkers, Beyond Pesticides advances improved protections from pesticides and alternative pest management strategies that reduce or eliminate a reliance on pesticides.” (The letter is available HERE: Beyond Pesticides – ISAC Comment )

 I receive emails from Beyond Pesticides at least once a week, alerting me to opportunities to influence the laws and policies that regulate pesticide use in America.  As you might expect, the frequency of those alerts has accelerated a great deal in the past year, as the federal government is actively engaged in the process of dismantling many federal regulations, including those that regulate pesticides.

 The National Invasive Species Council recently invited the public to submit public comments in answer to a few specific questions, in preparation for the next meeting of the Invasive Species Advisory Council.  Today I am publishing an excerpt of the letter of Beyond Pesticides in answer to those questions (some emphasis added).  I am doing so because I consider this letter a wise and informed critique of the entire concept of “invasive species” and the pesticides used to eradicate them.

 I am also alerting the readers of Million Trees to the opportunity to attend the annual forum of Beyond Pesticides in Irvine, California, April 13-14, 2018.  Information about that meeting is available below.

 Million Trees

“The National Invasive Species Council (NISC) posed four questions for public input to the forthcoming meeting of the Invasive Species Advisory Council (ISAC). We find it most helpful to begin with the fourth: “How can NISC foster the development and application of innovative tools and technologies to enable the prevention, eradication, and control of invasive species in a more timely and effective manner?”

In order to address this question, NISC and ISAC need to first address the question, “What is an ‘invasive species’?”

‘Invasive species’ have frequently provided a reason for dispersing toxic chemicals in the environment, often with a sense of urgency and an assumed indisputable benefit. This unsupported (and sometimes unstated) assertion of benefit is a claim to virtue that allows environmental harm instead of preventing it.

In the context of other federal, state, and local laws, the regulatory definition of ‘invasive species’ gives broad authority to agencies to use all means at their disposal to rid the jurisdiction of non-native organisms causing economic harm, as well as harm to health and the environment. Many local ordinances that ban or restrict pesticide use make an exception for ‘invasive species,’ presumably under the mistaken assumption that in doing so they are protecting the environment. Instead, they are allowing environmental harm through the spread of toxic substances.

The use of the term ‘invasive species’ as a claim to virtue that is used to promote any and every attempt to exterminate any unwanted organisms is very disturbing. It is important to understand the problems that lead to the use of toxic chemicals, beginning with the cause. In the case of situations involving so-called ‘invasive species,’ we find that few, if any, involve species that are truly ecologically invasive—that is, capable of invading and persisting in intact ecosystems. Instead, such situations usually involve species that can take advantage of disturbed habitats (‘weeds’ or ‘weedy species’). As such, the emphasis should be placed on healing the disturbance (to which end, so-called ‘invasives’ may sometimes be helpful), rather than killing the opportunist colonizer.

We do not take the position that such opportunist colonizers should never be removed or managed. We do believe that the decision concerning whether such action should be taken should be based on the situation at hand and not on a claim to virtue that makes extermination of non-natives a righteous cause.

Redefining ‘invasive species’ to be limited to those species that can invade and damage intact ecological communities will directly ‘foster the development and application of innovative tools and technologies to enable the prevention, eradication, and control of invasive species in a more timely and effective manner’ (NISC) because resources will be directed only at those species that truly present an ecological threat. It will prevent those resources from being squandered in ways that are ecologically destructive.

The sharper focus that this redefinition will bring to the NISC and ASIC will enable them to explore approaches such as those that Beyond Pesticides has used in working with National Parks, local governments, and tribes to manage ecological problems in a way that is truly protective of biodiversity.”

Terry Shistar, Ph.D.
Board of Directors
Beyond Pesticides

Beyond Pesticides will soon hold its annual forum in Irvine, California, April 13-14, 2018.  As usual, the forum will include highly qualified speakers who are knowledgeable about so-called “invasive species,” and the evolutionary principles that raise questions about the necessity and futility of trying to eradicate them.   Two of the speakers are important to our local effort to stop the use of pesticides to eradicate non-native plant species:  Dr. Scott Carroll and Professor Tyrone Hayes.

Dr. Scott Carroll is an evolutionary biologist affiliated with UC Davis.  He has published several influential studies about the speed of adaptation and evolution that enables introduced plants to join native ecosystems without long-term negative consequences of their introduction.  He has coined the concept of “Conciliation Biology,” which advocates that we turn from efforts to eradicate non-native species in favor of a new approach which manages the co-existence of native and non-native species. 

Professor Tyrone Hayes (UC Berkeley) is best known for his criticism of the herbicide, atrazine, which is harmful to the frogs that he studies.  Unfortunately, Professor Hayes’ opposition to atrazine does not extend to the pesticides being used in the San Francisco Bay Area to eradicate non-native trees and prevent them from resprouting.  Professor Hayes accepts the premise that eucalyptus trees are detrimental to native plants, which justifies the use of herbicides to destroy them, in his opinion.  The herbicide that is used for that purpose (Garlon with active ingredient triclopyr) is just as toxic as atrazine.  Both are organochlorine products that bioaccumulate, persist in the environment for decades, and are endocrine disruptors. 

The Beyond Pesticides forum is likely to generate some lively discussion of the issues that are relevant in the San Francisco Bay Area.  Details about the conference are available HERE.  Beyond Pesticides makes every effort to make these forums affordable for activists.  I have attended two of these conferences.  They were excellent opportunities to learn more about pesticides, to meet other activists, and to get ideas about how to advocate more effectively for more responsible pesticide use in our community.

I am very grateful to Beyond Pesticides for their leadership in the effort to reduce pesticide use in the United States.  They are a reliable source of information about pesticides and their activism is an inspiration to those who are engaged in this effort on a local level.

Million Trees

Unseen City: A tribute to urban nature

It was pure pleasure to read Unseen City (1).  Unlike most nature writing, Nathanael Johnson asks readers to notice and appreciate the urban nature that we tend to take for granted.  Ironically, the plants and animals that we see every day and in great numbers do not get the attention they deserve.  Most nature writing tends to focus on rare and remote species to which we have little access and often laments their absence where we live.  Conservationists often advocate for expensive programs to reintroduce rare species to urban centers where they haven’t lived for decades, if not centuries.

Johnson’s focus on the ordinary species around us is refreshing.  We were happy to take a break from the usual hand-wringing about loss of biodiversity and instead enjoy the richness and beauty of the nature we have.  It is our loss when we ignore the nature we have. Johnson’s intense focus on urban species reveals that they are every bit as interesting as the rare species we seldom see.  Johnson’s approach to nature is analogous to the optimist’s “glass-half-full” approach to life.

Another appealing aspect of Johnson’s approach is that his story is told from the perspective of a young father, introducing his toddler daughter to the mysteries of nature.  One of our primary concerns about the museumification of our parks by native plant advocates is that children are being deprived of the opportunity to interact with nature.  Being required to stay on trails or observe from behind fences is no way for children to appreciate the complexity and beauty of the natural world.  Johnson takes his daughter deep into the weeds to experience nature in a physical, tactile way. 

A few examples of the homely creatures in our cities

Johnson wrote his book while living in San Francisco and then in Berkeley.  So, the species he encounters and studies are those with which we are all familiar.  Here are some of the creatures he tells us about, with a few of the interesting things we learn about them.

  • Pigeons are reviled by many serious bird watchers. In fact, they are remarkable creatures in many ways.  They mate for life and they are extremely devoted parents.  They tend to nest in the same place and their ability to find and return to that nest from long distances is one of the reasons why humans have formed intense relationships with them.  There is a long tradition of keeping homing pigeons that are raced by their keepers in competitions that occur all over the world.  The pigeons are taken long distances from their nests and then timed on how long it takes them to return home.  Johnson tells remarkable stories about how pigeons overcome challenging attempts to prevent them from finding their way home.
  • Eastern grey squirrel. Creative Commons

    Squirrels are both extremely agile and very resourceful. Here is an example of how squirrels defeated an attempt to keep them out of a bird feeder: “…squirrels had to climb up through a vertical pipe, leap onto a blade of a spinning windmill, cling to it, and then sail off on the right trajectory to land on a platform.  Then they had to go paw over paw upside down along a suspended chain that passed through a series of spinning disks, negotiate a revolving door, run through a slack canvas tube, and keep their balance while crossing a pole covered with slick spinning rollers.  From there, it was a six-foot jump to another tunnel, through which they had to ride a sliding vehicle made to look like a rocket ship by pushing it along with their paws.  Finally, there was an eight-foot jump to the food.” (1)  I retell this to story to spare our readers the pointless effort of trying to prevent squirrels from raiding their bird feeders.

  • Turkey vulture in San Jose, California by Dan DeBold. Creative Commons

    The turkey vulture is another underappreciated bird. They eat primarily dead animals and many of those animals died of diseases or toxic chemicals and are rotten and maggot infested when they are finally found (by smell) and eaten by the vulture.  The digestive and immune system of the vulture is capable of detoxifying chemicals and killing bacteria and viruses in the dead animal.  In other words, the vulture is cleaning up the remains of dead animals.  India has learned the value of vultures the hard way.  They killed many of their vultures with an anti-inflammatory drug they were feeding to their livestock.  When their vulture population dwindled, they were buried in dead animals, many dangerously diseased and toxic.  We eradicate animals at our peril because we often don’t understand the roles they are playing in the ecosystem.

Defending novel ecosystems

In addition to asking his readers to appreciate the positive qualities of the creatures in our cities, he also asks us to reconsider the deep prejudice against them that has become the conventional wisdom.  Plants and animals that people believe were transplanted by humans into places where they did not exist in the distant past are considered “alien invaders” that dominate their predecessors, driving them out and reducing biodiversity.

This narrative, which originated in academic science as “invasion biology” in the 1960s, has become a popular story with the media, which is always attracted to scary stories.  The media is significantly less interested in the peaceful resolution of their horror stories.  With few exceptions, an introduced species that initially seems to be a problem eventually fades into the woodwork to become just another player in the ecosystem.  Johnson uses the Argentine ant as one of many examples of an introduced species that spread rapidly, but 20 years later has nearly disappeared.  In other cases, a species initially considered an unwelcome intruder becomes a valuable asset, such as zebra mussels which filter pollution from lakes and have become a source of food for diving birds.

Novel ecosystems are the future

Johnson concludes his book with this reminder that novel ecosystems have been created by human disturbance and that we should be grateful for the plants and animals that are capable of surviving our abusive treatment of the planet:

“The species that I’ve written about here are, at best, invisible, and at worst, reviled.  We honor least the nature that is closest to us.  As Courtney Humphries put it in Superdove, ‘We create and destroy habitat, we shape genomes, we aid the worldwide movement of other species.  And yet we seem disappointed and horrified when those plants and animals respond by adapting to our changes and thriving in them.’

“Because they are associated with human disruption, the organisms that spring up from our footprints look like corruptions of nature.  But I’ve come to see it the other way around:  These species represent nature at its most vital and creative.

“Nature never misses an opportunity to exploit a catastrophe.  When humans bulldoze and pave, nature sends in a vanguard of species that can tough it out in the new environment.  These invasive species are not nature’s destroyers, but rather its creators.  They begin setting up food webs, they evolve and diverge into new species.  Because humans purposefully import exotic plants—along with the insects, seeds, and microbes we accidentally bring in from around the world—cities are remarkable centers of biodiversity.  These creatures crossbreed, hybridize, eat one another, form cooperative relationships, and evolve.  And so, at a time when thousands of species are at risk of extinction because of our destruction of wilderness, new species are springing up in the new habitats we have created.” (1)

Worshipping the rare at the expense of the common

The ONLY known Raven’s manzanita plant is in the San Francisco Presidio. Its exact location is a secret to protect it.

Vast sums of money are being spent in often futile attempts to reintroduce rare plants and animals to urban environments where they have not lived for a long time.  The National Park Service and San Francisco’s Natural Resources Division are having little success with their efforts to reintroduce Mission Blue butterflies.  After over 30 years, the National Park Service has still not successfully germinated endangered Raven’s manzanita from seed.  These fruitless efforts are not just wasteful of resources, they also inflict damage on the environment by using pesticides and setting fires to eliminate competition and destroying trees to increase sunlight on rare plants and host plants of rare insects.

The veneration of rare plants and animals is often at the expense of the plants and animals that are adapted to present environmental conditions.  In Unseen City Nathanael Johnson invites us to place greater value on the ordinary creatures who are capable of living with us.  We can treat them with the respect they deserve by not destroying them in pursuit of a fantasy landscape populated by fantasy creatures that are not capable of surviving the changes we have made in the environment.

  1. Nathanael Johnson, Unseen City: The majesty of pigeons, the discreet charm of snails and other wonders of the urban wilderness, Rodale Wellness, 2016

Embers start spot fires: The real and the imagined stories

Bay Nature recently published an article about the 1991 fire in the East Bay Hills and the closely related belief that such a fire can be prevented in the future by destroying all non-native trees.  To Bay Nature’s credit, it was a more balanced article than most.  Although the article was heavily weighted in favor of those who want to destroy all non-native trees in the hills, several defenders of our urban forest were also interviewed.

However, the article contains a fantasy about future fires that feeds into the fear of fire that has been fostered by those who advocate for removing all non-native trees:

“A strong wind begins blowing over the hills from the east. And then somehow—maybe a spark from a car, maybe a tossed cigarette—the whole dry, airy mess catches fire.  Now the flames on the ground are 30 feet high and even higher off the boughs, roaring like a jet engine. At the fire’s edges, trees appear to explode as the volatile oils in their leaves reach their boiling point and vaporize. The heat of the fire forms a convection column, with 60-mile-per-hour winds that rip burning strips of bark from the trees and toss them upward. This is another of blue gums’ talents—its bark makes ideal braziers. Tucked away inside a rolled-up strip of bark, a fire might live for close to an hour and fly 20 miles.” (1)

Although we have read many times in the plans to destroy trees that eucalyptus casts embers starting spot fires, we have never seen such an extreme description of how far embers could travel while still on fire and capable of starting a spot fire.  So, we tracked down the source of this theoretical scenario with the help of the author who cited this as the source of the theoretical scenario:  “The potential for an internally convoluted cylinder of bark to be transported tens of kilometres in a continuously flaming state is indicated by the sample that maintained flaming combustion for the entire experiment…This would correspond to a flameout time of almost 2000 s for a sample 2700 mm long, a lofted height of 9600 m and a spotting distance of ~37 km.” (2)

First let’s translate that quote into measurements we commonly use to appreciate how extreme this particular test was:  “This would correspond to a flameout time of almost 33 minutes for a sample 9 feet long, a lofted height of 6 miles and a spotting distance of 23 miles, traveling at 41 miles per hour.”  That is a very long ember, lofted a great distance at a great speed (but NOT 60 mph), staying lit for a long time (but NOT “close to an hour”).  

Theory vs. Reality

The study that was the source of the extreme prediction in Bay Nature about the distance that burning embers can travel was conducted on samples of Eucalyptus viminalis bark (NOT Blue Gum Eucalyptus, E. globulus) “tethered in a vertical wind tunnel.”  These are not real-world conditions.  So, how does this theoretical study compare to real-world conditions?

The FEMA Technical Report about the 1991 fire in the East Bay Hills contains a map of the full extent of the 1991 fire.  As you can see on this map, the maximum distance from the northern-most edge of the fire to the southern edge of the fire is less than 3 miles…not remotely close to 20 miles.  In other words, embers could not have started fires 20 miles away because the fire wasn’t even close to 20 miles long.


The FEMA Technical Report doesn’t tell us what the wind speeds were during the 1991 fire, although they describe the wind as being strong at several times during the fire.  If there is any evidence that winds were as much as 60 miles per hour, it’s not evidence we have been able to find.  We found a source of wind speeds measured on the Bay Bridge, including historical records.  This website says the strongest wind measured since 2010 was 31 miles per hour in April 2013.  That suggests that 60 mph winds are probably unusual in the San Francisco Bay Area.

The FEMA Technical Report doesn’t report any observations of firebrands or burning embers from eucalyptus.  The report mentions embers twelve times, but identifies the source of those embers only once.  In that one case, the source of embers was “a growth of brush”….not a eucalyptus tree or any tree, for that matter.  There are anecdotal reports of finding debris from the fire as  far as San Francisco, but no reports that the debris was still on fire or that it started another fire.

US Forest Service study of embers in actual fires

US Forest Service participated in a comprehensive study of “spotting ignition by lofted firebrands” based on actual wildfires all over the world, including the 1991 fire in the East Bay Hills. (3)  There is nothing in that study that corroborates the claim that eucalyptus bark embers are capable of travelling 20 miles while remaining lit and therefore capable of starting spot fires:

  • “In the wildland-urban interface fires in California—Berkeley in 1923, Bel-Air in 1961, Oakland 1991—wooden shingles which were popular in California as roof material, assisted fire spread. Wooden shingles increase fire hazard owing to both ease of ignition and subsequent firebrand production.
  • “Unlike the flying brush brands which are often consumed before rising to great heights, the flat wood roofing materials soared to higher altitudes carried by strong vertical drafts…”
  • The only firebrand found in the 1991 Oakland Hills fire was found approximately 1 km (.6 mile) west from the perimeter of the fire. It was a cedar shingle.  Here is a photograph of that shingle:  ember-1991-fire-2
  • Cylinder shaped embers do not travel as far as flat particles. Firebrands in the shape of cylinders were found to have a maximum spotting distance of 2050 meters, because “cylinders always fall tumbling.”
  • “The increased burning time inherent in larger firebrands was cancelled out by an increased time of flight because larger firebrands move more slowly.”
  • In a study of 245 extinguished fires, experiments and simulations, and observing 48 wildfires, “The longest spotting distance was observed as 2.4 km.”

This comprehensive study of actual wildfires all over the world finds no evidence of embers capable of travelling 20 miles while still burning and starting spot fires.  It reports that wooden shingles were the only observed burning embers in the 1991 fire and that wooden shingles are particularly vulnerable to being lofted as embers in a wildfire.  There are countless houses in the East Bay Hills covered in wooden shingles, yet instead of addressing that obvious source of embers, we are destroying blameless trees.

Developing the Cover Story

Claims about the extreme flammability of eucalyptus have escalated in the past 15 years as opposition to destroying trees and associated pesticide use has escalated.  Nativists have become increasingly dependent on flogging the fear factor as their other storylines have been dismantled by empirical studies and reality:

  • Monarch butterflies roosting in eucalyptus tree.
    Monarch butterflies roosting in eucalyptus tree.

    The “invasiveness” of eucalyptus has been downgraded by the California Invasive Plant Council from “moderate” to “limited,” their lowest rating. There is little evidence that eucalyptus is invasive unless planted along streams and swales that carry their seeds.

  • There are many empirical studies that find that all forms of wildlife—such as insects and birds—are served equally well by both native and non-native plants. Some iconic species—such as Monarch butterflies, bees, hummingbirds, hawks, owls—are dependent upon eucalyptus for winter nectar and safe nesting habitat.
  • Huge global studies of biodiversity report that the introduction of non-native species has resulted in no net loss of biodiversity. This is particularly true of introduced plants.  There is not a single instance of extinction caused by a non-native plant in the continental United States.
  • Climate change is making nativism increasingly irrelevant. California’s native conifers, oaks, and redwoods are dying by the millions.  Unless we want a treeless landscape, we must plant tree species that are capable of tolerating changed climate conditions.

    Owl nesting in eucalyptus, courtesy urbanwildness.com
    Owl nesting in eucalyptus, courtesy urbanwildness.com

These studies have left nativists with few tools to justify the eradication of non-native plants.  We can see the development of the FIRE!! cover story in the archives of the conferences of the California Invasive Plant Council.  In 2004 Cal-IPC held a workshop regarding exotic trees and shrubs.  Over 30 representatives of major managers of public lands attended, such as National Park Service, San Francisco’s Natural Areas Program, Marin County Open Space, etc.  The record of this meeting reflects the dependence upon fire to justify the eradication of non-native shrubs and trees:  “Golden Gate National Recreation Area:  ‘inform public ahead of time; use threat of fire danger to help build support for invasive plant removal projects.’”  The Golden Gate National Recreation Area—a National Park–advises other land managers to frighten the public into accepting the loss of their trees. 

Subterfuge is also recommended to land managers to hide the eradication of shrubs and trees from the public:  “To avoid public upset, drilling around into tree buttress roots and injecting 25% glyphosate…Trees die slow and branches fall slowly, so won’t pose an immediate hazard.”  In other words, land managers were advised to kill trees using a method that won’t be visible to the public. 

Perhaps most disturbing of all is that those who attended this workshop admit that they don’t really know if eucalyptus trees are more flammable than native vegetation and some doubt that they are:  “People are afraid of fire.  Help them understand Eucalyptus trees and other invasive plants are very fire hazardous.  Is there any solid research about Eucalyptus and fire?  Are Eucalyptus and brooms any greater fire danger than native chaparral?”  In other words, even those who wish to destroy non-native shrubs and trees seem to understand that fire is a cover story for which no supporting evidence exists. The evidence has been fabricated to support the cover story.

We now seem to live in a fact-free world in which various interests can make things up and distribute them on the internet with impunity.  The mainstream press is dying and is being replaced by fact-free social media.  If we are to protect ourselves from such manipulation, we must drill down into these storylines.  In the case of eucalyptus, we have debunked the myth that it is more dangerous than the replacement landscape.  Now it’s up to us to disseminate that information far and wide as an antidote to fear-driven nativism. 

  1. Zach St George, “Burning Question in the East Bay Hills: Eucalyptus is flammable compared to what? Bay Nature, October-December 2016
  2. James Hall, et. al., “Long-distance spotting potential of bark strips of a ribbon gum (Eucalyptus viminalis), International Journal of Wildland Fire, 2015, 24, 1109-1117
  3. Eunmo Koo, et. al., “Firebrands and spotting ignition in large-scale fires,” International Journal of Wildland Fire, 2010, 19, 818-843

Beyond the War on Invasive Species

Tao Orion is the author of Beyond the War on Invasive Species:  A Permaculture Approach to Ecosystem Restoration, the latest in the rapidly growing literature about the futile and destructive attempts to eradicate non-native species.  Ms. Orion will give a workshop at a PLACE for Sustainable Living on Thursday, September 17, 2015:

“Rethinking Invasive Species from a Permaculture Perspective”

Thursday, September 17, 2015, 6-8 pm

PLACE for Sustainable Living

1121 64th St, Oakland, CA 94608

Donations $12-$25 requested

Update:  This is the answer PLACE for Sustainable Living gave to a question about wheelchair accessibility:  “It is not wheel chair accessible yet – we have carried wheelchair persons up the steps with their wheelchairs – we can arrange for that. And the yard is filled with chipwood, wheel chairs have rolled over fine, but not sure if everyone in them can push through. Our friend, male, can push through fine.”  Please contact PLACE for Sustainable Living directly if you have specific questions about accessibility.  (addendum dated 9/10/15)

Update #2:  Ms. Orion’s presentation has been cancelled because the venue is not wheelchair accessible.  CUIDO (an organization which represents disabled people) asked that it be moved to a facility with wheelchair accessibility or cancelled.  Such a facility could not be found, so it has been cancelled.  

Update #3:  Some adjustments have been made in plans for Ms. Orion’s presentation which are apparently acceptable to at least some members of the disabled community.  Ms. Orion has therefore decided against cancelling it.  Sorry for the confusion.

Ms. Orion is visiting the Bay Area from the Willamette Valley in Oregon, where she has a small farm in the country.  She has a degree in agroecology and sustainable agriculture from UC Santa Cruz and she has studied at the Columbines School of Botanical Studies in Eugene, Oregon.  She teaches permaculture design at Oregon State University and a non-profit sustainable-living educational organization.  She has also worked as a permaculture designer for ecological restorations.

Beyond the War on Invasive Species

Beyond the War on Invasive SpeciesThe first chapter of Ms. Orion’s book is a breakthrough because it is an explicit indictment of pesticides used by so-called “restoration” projects.  Although previously published books were critical of invasion biology and the ecological industry it spawned, pesticides were barely mentioned in them.  In contrast, it is primarily the use of pesticides in ecological “restorations” that convinced Ms. Orion that the war on invasive species is doing more harm than good.

Concern about unwanted plants – AKA weeds – is as old as human engagement in agriculture, that is, thousands of years old. And most of the plant and animal species now considered “invasive” were introduced by humans to serve a variety of purposes, including aesthetics, such as mute swans and multiflora roses.  Some of these introduced plants and animals had unintended consequences such as competing with native plants and animals for available resources.  Concern – even regret – about these introductions has increased greatly in the past 25 years.  Attempts to manage these introductions has escalated from import limitations to fines and penalties and finally to attempts to eradicate plants and animals with pesticides.

The role of the pesticide industry in the escalating war on “invasive” species

Ms. Orion turns to the public record to make the case that the current focus on eradicating introduced species using pesticides was influenced by business interests.  She points out that the federal Invasive Species Advisory Committee is a consortium of academic, professional, and business interests, including at least two people who are employed by manufacturers of pesticides.  They make invasive species management policy recommendations to the National Invasive Species Council (NISC), created by Executive Order in 1999.  The federal government is spending over $1 billion annually on research and control of “invasive” species, including pesticide applications.

National Invasive Species Council

The NISC is modeled after the California Exotic Pest Plant Council, created in 1992.  That Council is now known as the California Invasive Plant Council (Cal-IPC).  Cal-IPC brought together representatives from government agencies and non-profit environmental organizations, as well as manufacturers of pesticides and spray equipment:  “Monsanto has sponsored Cal-IPC since its inception and both DuPont and Dow AgroSciences have also supported the group.”  (1)

The first annual conference of Cal-IPC in 1993 featured an employee of Monsanto, Dr. Nelroy Jackson.  Jackson’s presentation to Cal-IPC stated that “chemical weed control is the optimal method for control and removal of exotic plant species during…most native habitat restoration projects.” 

Jackson’s involvement in escalating attempts to eradicate introduced species is troubling, but is not the only example of such collaboration between the “restoration” industry and the manufacturers of pesticides.  The Weed Science Society, which advocates for “research, education, and awareness of weeds in managed and natural ecosystems,” has employees of Dow Agrosciences, Syngenta, and Dow Chemical on its board of directors.  Those manufacturers of pesticides, as well as Monsanto, Bayer Crop Science, Dupont, and BASF Corp are also donors to the weed society, at the highest levels of donations.

The manufacturers of pesticides also influence the “restoration” industry by investing and participating in the consulting firms that write environmental impact reports for ecological “restoration” projects, such as Tetra Tech (which wrote the draft Environmental Impact Report for San Francisco’s so-called Natural Areas Program).

The manufacturers of pesticides influence public policy regarding ecological “restoration” by making large tax-deductible contributions to many land-grant universities that conduct research on agriculture:  “A 2012 Report from Food and Water Watch found that nearly 25% of funding for agricultural research at public universities comes from private companies.”  (1) This is one of many reasons why there is so little research done on non-chemical approaches to ecological restoration.

As disturbing as this collaboration between the government and the pesticide industry is, the evidence of the relationships between trusted non-profit environmental organizations and corporate interests is even more so.  Nature Conservancy, National Audubon Society, and Ducks Unlimited all have close relationships with the manufacturers of pesticides and receive funding from them.

Ms. Orion then describes the use of pesticides by the “restoration” industry.  She also describes some of the damage pesticides are known to do, such as killing microbes in the soil and binding minerals in the soil.  She describes the persistence and mobility of pesticides in the environment.  She describes the inadequacy of testing and regulation of pesticides in the United States.  These issues are well known to the readers of Million Trees, so we won’t repeat them here, but new readers can click on the blue links to visit posts about those issues.

All introduced species are presumed to be harmful

Ms. Orion’s next chapters are more similar to the books that precede hers.  There are several examples of specific “invasions” that illustrate the point that “invasive” species are usually symptoms of changes in the environment, rather than causes of those changes.  Attempting to eradicate them does not reverse the changes in the environment and often causes more environmental damage.  “Invasive” species are often performing valuable ecological functions that are not understood until they are eradicated.  We have reported many examples of these issues and won’t repeat them here.  However, Ms. Orion’s telling of the history of Asian Carp in the Mississippi River and the Great Lakes was new to us and is well worth a retelling.

Song dynasty painting attributed to Liu Cai (c.1080–1120). Contains various types of fish and other marine animals, such as goldfish, perch, catfish, carp, minnows, bass, and shrimp.
Song dynasty painting attributed to Liu Cai (c.1080–1120). Contains various types of fish and other marine animals, such as goldfish, perch, catfish, carp, minnows, bass, and shrimp.

Asian carp has been a mainstay in the diet of the Chinese for several thousand years, according to their historical literature.  Asian carp are well adapted to aquaculture techniques, so they have the potential to replace or supplement other sources of protein.  They were introduced to the Midwest in the early 1800s and they spread throughout the Mississippi River many decades ago.  Although they are prevalent in the Mississippi River, they have not driven any native fish to extinction.  Yet, despite their usefulness and the lack of evidence that they have caused any harm, they suddenly became the latest invasion crisis when it was feared they would soon enter the Great Lakes.  A government fisheries biologist put that fear into perspective:

“We are trying to keep invasive Chinese carps out of the Great Lakes, to protect an invasive (yet purposefully stocked) Pacific salmon fishery, which was stocked as a management tool to control hyper-abundant alewifes, another invasive fish species, because the native piscivore, the Lake Trout, was nearly wiped out by another invasive species, the sea lamprey, because people built the Welland Canal around Niagara Falls to promote intercontinental shipping deep into the Great Lakes basin.” (1)

It makes the head spin to follow the “logic” of this sequence of events, which we paraphrase, “we solved one problem by creating another, then we solved that problem by creating another…ad infinitum.“  This is an ecosystem that has been radically altered by man, including reversing the flow of the Chicago River which connects the Mississippi River to the Great Lakes to solve Chicago’s sewage problems.   The water is warmer, polluted with agricultural runoff, and there is no longer a seasonal, cleansing water surge.  These changes in the environment set the stage for the arrival of Asian Carp in the Great Lakes.  The habitat for native fish has been radically altered such that removal of Asian carp from the river is an irrelevant, inconsequential improvement of habitat needed by native fish.

Despite what would seem overwhelming evidence that Asian carp could be a valuable food source and that being rid of them is unlikely to benefit anyone, here is a brief list of what has been done so far to try to prevent them from entering the Great Lakes:

Fish kill using rotenone. http://www.encyclopedia.com/doc/1E1-X-rotenone.html
Fish kill using rotenone. http://www.encyclopedia.com/doc/1E1-X-rotenone.html

  • US Army Corps of Engineers constructed a submerged electric fence to shock and kill the fish as they enter the Great Lakes. The fence cost millions of dollars but is largely ineffective.
  • The Illinois Department of Natural Resources dumped 2,200 gallons of rotenone into sanitary and ship canals feeding into the Great Lakes. This poison kills all gilled animals. The result:  “Among the tens of thousands of dead fish, researchers found one Asian carp.” (1) This fiasco cost $3 million.
  • Other researchers have suggested a system of strobe lights and bubble and sound barriers to stop the northward migration of Asian carp.

Permaculture philosophy

Ms. Orion’s closing chapters reflect her training in permaculture design.  She considers the tending of the wild by Native Americans a model for ideal stewardship of the land.  And she advocates for land management strategies that reflect the realities of our changed environment and are sustainable into the future.  We will let her speak for herself:

“Holistic restoration planning requires an honest accounting of what has come to pass as well as a comprehensive view of what we can do about it.  The problems are complex, and the solutions are likely to be more so…Navigating from a paradigm that views invasive species as scourges to one that looks at them as opportunities for deeper ecological and economic engagement will take time and commitment, especially because the old paradigm is so entrenched politically, economically, and academically.  The tide is shifting though, as more and more of us are coming to realize that the herbicide-based eradication approach to restoration is outmoded—a futile attempt to regain an imagined past—and we need to be focusing our time, resources, and energy on adapting to the future.” (1)

Please show your support for Tao Orion and her book by attending her workshop on Thursday, September 17th.


(1) Tao Orion, Beyond the War on Invasive Species:  A Permaculture Approach to Ecosystem Restoration, Chelsea Green Publishing, 2015 

“Weed Whackers, Monsanto, glyphosate, and the war on invasive species”

coyote in oxalis field. Copyright Janet Kessler
coyote in oxalis field. Copyright Janet Kessler

Harper’s Magazine describes itself: “the oldest general-interest monthly in America, explores the issues that drive our national conversation, through long-form narrative journalism and essays…”  Harper’s has just published an article by Andrew Cockburn, an experienced investigative journalist with an impressive track-record of informing the public of some of the darkest secrets in our country.  The article is available here:  Cockburn – Weed Whackers

Invasion biology and the “restoration” industry it has spawned deserved his attention and we are indeed fortunate that he has brought his journalistic skills to this task.   The public is largely unaware of the billions of dollars of taxpayers’ money being wasted on futile attempts to eradicate “invasive” plants.  There is even less knowledge of the quantities of pesticides being used by these projects or the toxicity of those pesticides.

Mr. Cockburn has interviewed many of the key players in this crusade against nature, on both sides of the controversy.  And he has visited specific projects to illustrate one of his key points:  “invasive” species are symptoms of environmental change, not the cause of them.

This article ( Cockburn – Weed Whackers )  deserves to be read, so we will not summarize it further.  Please share it with your friends, whether they are native plant advocates or critics of invasion biology.  We are deeply grateful to Mr. Cockburn for his even-handed treatment of this controversial issue, which is dividing communities in the San Francisco Bay Area.

Mount Sutro Forest. Courtesy Save Sutro
Mount Sutro Forest. Courtesy Save Sutro

Spartina eradication: Herbicides are their dirty little secret

This is a good news/bad news story about the eradication of non-native Spartina marsh grass and the impact it has had on the population of endangered California Clapper Rail:

  • Spartina alterniflora, Smooth Cordgrass.  USDA photo
    Spartina alterniflora, Smooth Cordgrass. USDA photo

    The good newsUS Fish & Wildlife has temporarily halted efforts to eradicate non-native Spartina (Spartina alterniflora) in the San Francisco Bay Area because the population of endangered California Clapper Rail has declined by 50% during the period of eradication efforts from 2005 to 2011. (1)  This problem was identified several years ago and was attributed to the lack of cover for the rail as a result of eradication of non-native Spartina, which grows more densely, taller, and doesn’t die back in winter as the native Spartina does. (2)

  • The bad news:  US Fish & Wildlife attributes this negative impact on the Clapper Rail population on the slow recovery of native Spartina (Spartina foliosa). 

    Spartina foliosa - USFWS
    Spartina foliosa – USFWS

    They do not acknowledge that non-native Spartina provides superior cover compared to the native species.  Nor do they acknowledge that non-native Spartina was killed with herbicides.  Therefore, they do not consider the possibility that the slow recovery of native Spartina may be attributable to the herbicides that were used to kill the non-native plant.  They also continue to claim that the recovery of the endangered California Clapper Rail depends upon the return of native Spartina, despite the overwhelming evidence to the contrary.  The California Clapper Rail is a sub-species of Clapper Rail; the Clapper Rail is abundant on the East and Gulf Coasts and not endangered perhaps because of the superior cover provided by Spartina alterniflora on those coasts. (3)  Based on these fictions, US Fish & Wildlife proposes a new strategy that will simultaneously eradicate non-native Spartina while intensively planting native Spartina.  (1)

We have been following the Spartina eradication project since 2011.  For the benefit of new readers, we will review the issues with a few excerpts from previous posts on Million Trees.

Spartina alterniflora:  Treasured on the East Coast, reviled on the West Coast

Spartina alterniflora (Smooth Cordgrass) is a species of marsh grass native to the Atlantic and Gulf coasts of the United States, where it is considered a valuable plant making important contributions to the coastal ecology:

  • Its dense growth provides protection against storm surge and “erosion control along shorelines, canal banks, levees, and other areas of soil-water interface.” (4)
  • It filters nutrients, sediments and toxins from the water that flows off the land before reaching the ocean, acting as a natural water treatment facility.
  • It provides cover and food for birds, mammals and marine animals that live in the coastal marsh.

Where Smooth Cordgrass has died back in its native range, the dieback has been considered a serious environmental threat:

  • In 2001 the Governor of Louisiana declared a “state of emergency” when Smooth Cordgrass declined and the state obtained $3 million of federal funding to study and hopefully reverse the decline.  This study resulted in the development of a method of aerial seeding of Smooth Cordgrass to restore declining areas of marshland. (5)
  • A similar, but smaller dieback of Smooth Cordgrass in Georgia led to a collaborative research and on-going monitoring effort by 6 research institutions in Georgia.
  • Similar dieback of Smooth Cordgrass has been reported as far north as the coast of Maine.  A researcher at the Connecticut Agricultural Experiment Station is quoted in that report as saying, “In New Orleans, if their marshes were intact, the storm surge of Katrina would not have reached the levees.” (6)

 The war on Smooth Cordgrass on the West Coast

Smooth Cordgrass is not native on the Pacific Coast of the United States.  Therefore it is treated as an alien invader to be eradicated with herbicides:

  • $24 million was spent to eradicate Smooth Cordgrass in San Francisco Bay and Willapa Bay from 2000 to 2010 (7)
  • $16.3 million is projected to be spent on the entire West Coast from 2011 to 2020 (7)

Spartina is being eradicated with an herbicide, imazapyr.  This is a new herbicide about which little is known.  The analysis that was done to justify its use in the Spartina eradication project admits that no studies have been done on its effect on shorebirds, including the endangered Clapper Rail. 

The Material Safety Data Sheet mandated by the Environmental Protection Agency tells us that imazapyr is “not readily biodegradable.”  So, in the event that we eventually learn that this herbicide is harmful to shorebirds and/or to us, we probably should assume that it will still be in the environment in the nearly 200 sites in the San Francisco Estuary on which it has been sprayed.  Imazapyr is also being sprayed–sometimes from helicopters–in hundreds of places along the West Coast, including Oregon and Washington.

Imazapyr is often mixed with glyphosate by the Spartina eradication project.  Glyphosate is a non-selective herbicide.  That is, it kills any plant it is sprayed on at the right stage of its growth.  But imazapyr is far more insidious as a killer of plants because it is known to travel from the roots of the plant that has been sprayed to the roots of other plants.  For that reason, the manufacturer cautions the user NOT to spray near the roots of any plant you don’t want to kill.  For example, the manufacturer says explicitly that imazapyr should not be sprayed under trees, because that tree is likely to be killed, whether or not that was the intention. 

Furthermore, no tests have been conducted on the toxicity of combining multiple pesticides in a single application.  Therefore, we know nothing about the possible synergistic effects of combining imazapyr and glyphosate. 

These facts about the herbicides used to eradicate non-native Spartina bear repeating.  The main herbicide being used is known to be mobile in the soil and persistent in the environment.  The herbicide with which it is often mixed is an indiscriminate killer of any plant on which it is sprayed.  Therefore, the likelihood that these herbicides will prevent the establishment of the new plantings of native Spartina should be taken into consideration.  The entire enterprise seems deeply flawed, both harmful and futile. 

Bringing it home to the Bay Area

So, what does this have to do with you?  If you are concerned about pesticide use, you might be interested in the fact the East Bay Regional Park District (EBRPD) used 203 gallons of imazapyr in 2009 and 121 gallons in 2010 for the sole purpose of eradicating Spartina on their properties.  We don’t know how much imazapyr EBRPD used in 2011, 2012 and 2013, because they haven’t published a report of pesticide use since 2010.  Since their properties are only on the east side of the San Francisco Bay, we should assume that at least that much imazapyr was used by land managers on the west side of the Bay.

 Displacement of Clapper Rails in San Francisco

California Clapper Rail.  British Wikipedia
California Clapper Rail. British Wikipedia

In July 2011, a Clapper Rail was seen and photographed at Heron’s Head in southeastern San Francisco.  There was quite a bit of excitement about this sighting because a Clapper Rail had not been seen in San Francisco for decades.  That excitement dissipated when we learned more about where this bird came from, which provided a probable reason for its arrival.

The Clapper Rail was wearing a radio collar that had been put on him and 109 other rails by the USGS to track their movements.  He had moved from Colma Creek, 11 km south of Heron’s Head, which is one of nearly 200 Spartina “control sites” in the San Francisco Estuary.  The bird sighted at Heron’s Head is one of three Clapper Rails that have left Colma Creek since 2007, when the radio collars were placed.  The Spartina control project has been going on for over 10 years, so we have no way of knowing how many Clapper Rails were displaced prior to 2007.  In 2012, non-native Spartina at Heron’s Head was sprayed with herbicides.  Where did the Clapper Rails go from there?  Was there anywhere left for them to hide?

Pesticide Application Notice, Heron's Head, 2012
Pesticide Application Notice, Heron’s Head, 2012

As our readers know, native plant advocates claim their “restoration” projects benefit wildlife.  They can offer no evidence for this claim.  But there is considerable evidence that proves them wrong.  The endangered California Clapper Rail is one such case.

(1)     Adam Lambert et.al., “Optimal approaches for balancing invasive species eradication and endangered species management,” Science, May 30, 2014, vol. 344 Issue 6187

(2)     “West Coast Governors’ Agreement on Ocean Health, Spartina Eradication Action Coordination Team Work Plan,” Released May 2010, page 12

(3)     Cornell Ornithology Lab:  http://www.allaboutbirds.org/guide/clapper_rail/id

(4)     “Smooth Cordgrass,” USDA/NRCS Plant Fact Sheet.

(5)  Dorset Hurley, “Geogia’s Marsh Die Back and Louisiana’s Marsh Browning,” Altamaha Riverkeeper

(6)  “What’s killing off our salt marshes,” Going Coastal Magazine, September 15, 2008

(7) “West Coast Governor’s Agreement on Ocean Health,” May 2010, page 5-6

Methods used by land managers to control “invasive” plants

It’s not easy to find information about herbicide use by land managers.  We make inquiries and public records requests of all the managers of public lands in the Bay Area.  Despite these persistent efforts, we have never been confident that we have the complete picture.  We are therefore grateful for a recent survey conducted by the California Invasive Plant Council (Cal-IPC) of land managers—public and private—about the methods they use and for what purposes.  The following charts tell us what Cal-IPC learned from their survey.

Cal-IPC sent surveys to 100 land managers who described the lands they managed as follows:

Organization* Response
Local agency 54%
Federal agency 53%
State agency 48%
Land trust or other private landowner 40%
Private consultant 26%
Other (nonprofit, forestry company, utility, regional park district, conservation district) 27%
*multiple employers

How frequently are the following objectives part of land managers’ reason for managing invasive plants?

Cal-IPC Survey 5

Non-herbicidal methods used by land managers to control invasive plants






Pulling with hand tools





Digging with hand tools





Cutting with pruners or loppers





Weed whacking with string or plastic blade





Cutting with hand saw or chainsaw





Mowing with large equipment





Brushcutting with metal blade










How often do land managers use herbicides for invasive plant control?

Cal-IPC Survey 4

What methods do land managers use to apply herbicides?






Foliar spray – spray to wet





Foliar spray – thin line





Foliar spray – low volume/high concentration





Basel bark application





Cut stump application





Drill and inject application





Girdling or frilling application





Broadcast application





Wick application





Aerial application





What herbicides are used by land managers?

Active Ingredient Response Percent
Glyphosate (e.g. RoundUp, Aquamaster)


Triclopyr (e.g. Garlon 3A, 4A)


Aminopyralid (e.g. Milestone, VM)


Clopyralid (e.g. Transline, Reclaim)


Imazapyr (Chopper, Stalker, Habitat, Arsenal)


Chlorsulfuron (e.g. Telar)


Fluazifop (e.g. Fusilade)


2,4-D (e.g. Amine 4, Weedar)


Acetic acid


Clove oil (e.g. Matran


Pelargonic acid (e.g. Scythe)


These charts were shown by the Executive Director of the California Invasive Council (Cal-IPC) at a meeting of the Integrated Pest Management Program in San Francisco on February 6, 2014.  He explained that the survey of land managers was conducted to assist Cal-IPC in preparation for a new edition of best management practices for managing invasive plant species in wildlands.  That publication will include risk assessments of the herbicides being used by land managers.  Cal-IPC is collaborating with the author of the risk assessments of potential herbicide use for the Marin Municipal Water District. We look forward to the publication of this document, which is anticipated in June 2014.  We hope that land managers will have confidence in the risk assessments of the herbicides they use, given the source of the information.

We make note of …..

According to this survey of land managers:

  • Ninety-four percent of land managers are using herbicides to control plants they consider “invasive.”  Sixty-two percent are using herbicides frequently.
  • Seventy-four percent of land managers are using Garlon, which is one of the most hazardous herbicides available on the market, as rated by the Environmental Protection Agency.
  • Many land managers are using Milestone and imazapyr which are known to be mobile in the soil as well as persistent in the environment according to the manufacturer’s label and the Environmental Protection Agency.
  • Foliar spray is the method used most frequently by land managers to apply herbicides.  This method of application has the potential to drift into non-target areas.

These practices are not adequately acknowledged in the environmental impact reports for the ecological “restoration” projects in the Bay Area.  Some environmental impact reports have not acknowledged the types of herbicides being used or the methods used to apply them.  None of the reports have acknowledged the quantities used by the projects nor have they acknowledged the toxicity of the herbicides.  The public is therefore unaware of the extent to which herbicides are being used by these projects and the risks associated with using them.