Even the most dedicated academic invasion biologists—such as Daniel Simberloff and Doug Tallamy—concede that not all introduced plants are invasive. However, they claim that all introduced plants have the potential to become invasive.
Early in the rise of invasive biology, over 25 years ago, much research effort was devoted to determining the factors that could predict which plants would become invasive. Theoretically, if we could predict an invasive future for an introduced plant we could make an early effort to eradicate them before they became entrenched, naturalized members of an ecosystem. At that point, most invasion biologists concede that landscape-scale attempts to eradicate non-native plants are futile.
The most recent attempt to identify the factors that contribute to “invasability” is a study led by Assistant Professor Moshen Mesgaran in the Department of Plant Sciences at UC Davis: “Invading plants remain undetected in a lag phase while they explore suitable climates.” (1) This study claims that it can take hundreds of years for non-native plants to become “invasive,” which the authors call “lag time.”
The study got my attention because it seemed obvious that the behavior of all plants, whether native or non-native, has changed greatly in the past 300 years, because of many changes in the environment, most notably climate change. What is described by the study as “lag time” between the time of the introduction of a non-native plant and its invasive behavior, seems primarily the predictable response of plants to climate and other changes that we should expect.
When I mentioned this study to one of my scientific advisors, he pointed out the most obvious flaw in the study, which casts doubt on the study’s conclusions. The study claims that plantain (Plantago lanceolata) had lag time of 177 years, the longest of any introduced plant in the United States: “Consider the common lawn weed Plantago lanceolata, otherwise known as ribwort or buckhorn plantain, which has the longest dormancy in the United States, according to the report. Noxious to livestock and native plants, the plant was introduced in the United States in 1822 and is found widely here.” (2)
Plantago lanceolata. Source: Wikipedia
In fact, plantain arrived in the US long before 1822 and was quickly widespread shortly after its arrival in the 17th century. Plantain arrived first to the East Coast with early settlers, along with many other weeds. John Josselyn visited New England in 1638 and 1663 and made a record of English weeds in New England—including Plantago lanceolata—that was published in the 19th century.
Native Americans of the Northeast also made a record of the arrival and spread of plantain in New England: Plantain “was called ‘Englishman’s foot’ by the Amerindians of both New England and Virginia, who believed in the seventeenth century that it would grow only where the English ‘have trodden & was never known to grow before the English came into this country.’” (3)
The arrival and rapid spread of plantain in the US is also immortalized by American popular literature. Henry Wadsworth Longfellow described the simultaneous arrival of white people and plantain, in the epic poem, Song of Hiawatha, published in 1855: “Wheresoe’er they tread, beneath them/Springs a flower unknown among us/Springs the White-man’s Foot in bloom.”
More recently, Daniel Mason described in his novel, North Woods, the arrival of plantain in the ballast of an English ship and its subsequent spread in the New World: “And there are seeds, uncountable, scattered in the humid loam: red clover, groundsel, spurrey, trefoil, meadow fescue, dandelion, hedge parsley, nonesuch, plantain. The voyage takes two months. On landing, the ballast is removed and dumped into the harbor. Much of it—the stones, the shells, the beads, the spectacles—sinks to the bottom of the bay. But the seeds, many of the seeds, enough of the seeds, rinsed loose of their swaddling earth, are freed into the breakers and float to shore.” (4)
Plantain arrived in the western US in the early 19th century, when the Spanish brought many weeds to the West from Mexico along with their herds of cattle. Weeds from the Old World were noticed and recorded by John C. Fremont when he visited the Sacramento Valley in 1844. He also mentioned that his horses ate the weeds, and “even the squaws he met ate it [red-stemmed filaree].” (3)
English plantain “was one of the nine sacred herbs of the Anglo-Saxons, and Chaucer and Shakespeare cited its medicinal qualities. It grows wild today in all the continents but Antarctica, as well as in New Zealand and a number of islands. It rates as one of the very hardiest of weeds in the world, and it will be with us forever, apparently.” (3)
Buckeye butterfly. Source: Wikipedia
“English plantain is a major host of the buckeye butterfly from coast to coast, and in New York and perhaps elsewhere it is being used by the Eastern Baltimore Checkerspot, Euphydryas phaeton, previously considered monophagous on the wetland Scroph Turtlehead, Chelone glabra. This provided an escape from a very narrow niche!” (5) There are many instances of butterflies using plantain as their host plant in scientific literature (6)
We also question the characterization of plantain by Professor Mesgaran’s research team as a “noxious weed” that is harmful to livestock. English plantain is not listed as a “noxious weed” by the state of California (7) and its “invasiveness” is considered “Limited” by the California Invasive Plant Council. English plantain is not considered toxic to horses or cattle, according to the results of internet searches.
Plantain arrived in the New World soon after it was discovered by the Old World. It spread quickly and is now a valued member of American ecosystems, as well as most ecosystems all over the world. As we often say in defense of harmless non-native plants, “What’s the beef?”
Professor Mesgaran’s study used herbarium and climate data to analyze “over 5,700 time series (species × regions) in 3,505 naturalized plant species from nine regions in temperate and tropical climates to quantify lags and test whether there have been shifts in the species’ climatic space during the transition from the lag phase to the expansion phase.” (1) This source of information was clearly not accurate in the case of English plantain, which has been in the US over 400 years and immediately spread everywhere. I can’t speak to the study’s report of “lag times” in other global regions.
Putting aside the inaccuracy of data used by the study to report the “lag time” between the arrival of introduced plants and evidence of invasive behavior, I summarize the findings of this study:
The behavior of plants vary from one place to another because growing conditions vary.
When the climate changes, vegetation changes in response.
This study claims that it can take hundreds of years for non-native plants to become “invasive.” The concept of “lag time” seems to suggest that all introduced plants have the potential to become invasive. This is not a new idea among invasion biologists who consider all introduced species a problem even when there is little evidence that they are. That school of thought expects us to prevent all plant introductions because they assume that all of them will be a problem in the future. The contrarian view is:
It is impossible to prevent all introductions of non-native plants because most are dispersed unintentionally or naturally.
The damage that is done to the environment by futile attempts to destroy non-native species is worse than the theoretical risks that some of them will eventually become a problem.
The resources used in the attempt to eradicate non-native species could be put to better use to benefit the environment, such as addressing the causes of climate change.
Every non-native plant contributes to biodiversity, which creates evolutionary opportunities to adapt to the changing environment. There is far more opportunity lost when harmless non-native plants are eradicated compared to their potential to contribute to biodiversity.
Many non-native plants are beneficial and are frequently functional substitutes for native species that are no longer adapted to the changed environmental conditions and climate.
Unfortunately, what might have been a straight-forward study (embedded in arcane jargon and complex statistical analysis) is flawed by inaccurate information about the “lag time” of specific plants in specific countries. The study claims that it took 177 years for plantain to become “invasive” in the US. In fact, plantain spread everywhere immediately after it was introduced in the 17th century and there is no evidence that it has done any harm where it lives. If we learn anything new from this study, it is that herbarium records are not a reliable source of information about the arrival and dispersal of introduced plants.
Much like the fossil record, herbarium collections can establish that a plant or animal lived in a specific place at a specific time, but they cannot provide negative evidence that the plant or animal wasn’t there or elsewhere prior to the time the specimen was collected. In any case, when plantain arrived in the US, there were few herbarium collections available to record its arrival.
This is not to say that herbarium collections are not useful for botanical research. Here are two specific examples of how herbarium collections have been used appropriately by scientists:
Angela Moles, an Australian scientist, used the collection of a university herbarium to measure the changes in plants that were introduced to Australia. The herbarium had samples of the same species of plants collected over a 60 year period from the same location. Professor Moles found that the plants had changed in significant ways. In a sense, they were becoming Australian plants in response to the biotic (other plants and animals) and abiotic (climate, soil, etc.) conditions of their new home. She predicted that if they weren’t yet genetically distinct from their ancestors, they soon would be. Professor Moles made a TED presentation 11 years ago about her findings that is available HERE.
Scientists used seeds in France’s National Botanical Conservatories collected in the 1990s and early 2000s to study how the plant had changed over a period of less than 30 years. The plant species they studied was capable of both self-pollination and cross-pollination by insects and other animals. They germinated the old seeds and compared their flowers with those now growing in the French countryside. They discovered that self-pollination by that plant species had increased 27 percent since the 1990s, probably in response to the significant decline in bee populations. That study was described by the New York Times.
No amount of obscure jargon and statistical analysis can compensate for flawed data: garbage in, garbage out.
“Invading plants remain undetected in a lag phase while they explore suitable climates,” Mohsen B. Mesgaran, Nature Ecology & Evolution, February 6, 2024
Email communication with Professor Emeritus Arthur M. Shapiro (UCD) with permission
“Matthew and Jonathan Douglas explicitly record oviposition on plantain in “Butterflies of the Great Lakes Region” (2005). I’m sure there are earlier such mentions.” Email communication with Professor Emeritus Arthur M. Shapiro (UCD) with permission
Below is my letter to California Assemblymember, Ash Kalra (District 25, San Jose), asking him to consider revising Assembly Bill 2509 so that it will reduce the use of pesticides in California to eradicate harmless and useful non-native plants. Please consider making this suggestion to your elected representatives in the California Legislature. AB2509 has the potential to reduce pesticide use in California if we make an effort to revise it as needed to accomplish that goal.
AB2509, your bill being considered by the California Legislature, will define “Integrated Pest Management” (IPM) and “invasive species.” The bill has the potential to reduce pesticide use in California’s parks and open spaces, but only if it is revised to accomplish that purpose. AB2509 is also an opportunity to improve the success of ecological restorations that begin by eradicating non-native plants considered “invasive,” by narrowing the target to those few species that are actually doing any harm.
In its present form (April 4, 2024), AB2509 defines invasive species, “to mean nonnative organisms that cause, or are likely to cause, economic or environmental harm, excluding humans, domestic livestock, specified domestic or domesticated species, and nonharmful nonnative organisms.”
That definition is based on Federal Executive Order 13112, which was passed 25 years ago, in 1999. We have learned a lot in the past 25 years about invasive species and the attempt to control them:
The climate has changed a great deal since 1999, and with it the environment, including the plants and animals that live in it. The native ranges of many plants and animals have changed and will continue to change.
We have learned that many introduced plants are often functional substitutes for native plants that are no longer adapted to the changed environment.
We have learned that insects are capable of rapidly adapting and evolving to make use of introduced plants.
We have learned, after trying to eradicate them for over 25 years, that most naturalized introduced plants cannot be eradicated.
We have learned that the herbicides being used to eradicate introduced plants are doing a great deal of harm to the environment and the animals who live in it. We now know that herbicides damage the soil, making it difficult for new plants to survive in sterilized soil, devoid of beneficial microbes and fungi.
We have learned that native plants don’t necessarily return after introduced plants have been eradicated. The damage done by eradication projects is often greater than the anticipated benefit.
Despite dire predictions to the contrary, there is no evidence that any introduced plant species has caused the extinction of a native plant species in California.
We need a new definition of invasive species that reflects these changes and accommodates the movement of plant and animal species needed for survival. We need a definition that does not attempt to stop adaptation and evolution. Like dynamic nature, our attempts to conserve nature must constantly evolve in response. We need a definition that distinguishes between actual harm and theoretical predictions of harm. We need a definition that does not require us to poison our public lands unnecessarily.
Please consider revising the definition of “invasive species” in AB2509 to reflect what we now know about introduced plants, such as:
“AB2509 defines invasive species to mean pathogens, diseases, and insects that are known to cause harm to plants and animals, including humans.”
In its present form, AB2509 also defines Integrated Pest Management as: “’Integrated pest management’ means an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control, habitat manipulation, modification of cultural practices, and use of resistant varieties. Pesticides are used only after monitoring indicates they are needed according to established guidelines, and treatments are made with the goal of removing only the target organism. Pest control materials are selected and applied in a manner that minimizes risks to human health, beneficial and nontarget organisms, and the environment.”
Integrated Pest Management (IPM) is not a new concept. Most public land managers have had IPM programs for over 25 years. Some have resulted in reduced herbicide use in developed areas, without corresponding reductions in public open space and wildlands.
San Francisco’s IPM program has significantly reduced herbicide use on developed public land, but herbicide used to eradicate non-native plants in one-third of park acreage known as “natural areas” has changed little, as shown in this graph:
Source: San Francisco Integrated Pest Management Program
East Bay Regional Park District has also reduced its use of herbicides in developed areas of the park, such as parking lots, picnic areas, and playgrounds, without reducing their use in wildlands where non-native plants and trees are eradicated:
If we want Integrated Pesticide Management Programs to reduce the use of pesticides in our public lands, we must define IPM to achieve that purpose by:
Changing the definition of “invasive species” to focus only on those introduced species that are known to cause actual harm. The expectation of “likely” harm without evidence of actual harm should not be used to justify pesticide use.
Explicitly defining the “guidelines” that determine if pesticides are needed in order to prevent their use on harmless and beneficial plants.
Avoiding the use of vague terms that can be interpreted differently from different perspectives, such as “use of resistant species.” Resistant to what? In whose opinion?
By not making empty promises such as claiming that pesticides can be used on non-native plants without doing any damage to non-target species. Because of drift, persistence, and mobility of pesticides in the soil, it is not possible to make such assurances, which give the public the mistaken impression that herbicides can be used without unintended consequences
Please consider a revised definition of Integrated Pesticide Management that will reduce pesticide use and preserve the vegetation that is capable of growing in today’s environment, such as:
“’Integrated pest management’ means an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control, habitat manipulation, and modification of cultural practices. Pesticides are used only after harm is documented, benefits of existing vegetation have been identified and weighed against harm, the health risks and environmental damage caused by herbicides is considered, and the outcome of eradication is determined to be positive, on balance.”
In conclusion, I will briefly describe my interest in invasion biology and the ecological restoration industry it spawned. My interest began over 25 years ago when my neighborhood park was designated a “natural area” by San Francisco’s Recreation and Park Department. When I moved to the East Bay, I learned that the native plant movement is equally committed to the eradication of introduced plants and the pesticides needed to accomplish that goal. I have visited many of these projects all over the Bay Area and elsewhere in California. I read the publications and attend the conferences of California Invasive Plant Council and California Native Plant Society so that I am as informed of their objectives and beliefs as I am of the academic criticism of invasion biology. I have had a website since 2010 that reports to the general public what I have learned about specific projects and the scientific evaluations of them. I invite you to visit my website to help you evaluate the advice I am sending to you today about AB2509. I can provide references for every statement I make in this letter, on request.
Thank you for your consideration and for your effort to reduce pesticide use in California.
Sincerely, Webmaster, Conservation Sense and Nonsense
CC: Patty Clary, Californians for Alternatives to Toxics Damon Connolly, Assembleymember, District 12 Jay Feldman, Beyond Pesticides Angel Garcia, Californians for Pesticide Reform Doug Johnson, California Invasive Plant Council Megan Kaun, Sonoma Safe, Ag Safe Schools Melinda MacNaughton, El Granada Advocates Margaret Reeves, Pesticide Action Network Jane Sellen, Californians for Pesticide Reform Nancy Skinner, Senator, District 9 Buffy Wicks, Assemblymember, District 15 Wildlife Conservation Board
Update, April 24, 2024:
The Assembly Agriculture Committee voted unanimously to pass AB2509 to the Appropriations Committee with no amendments.
Doug Johnson, Executive of Cal-IPC and Marc Landgraf, Santa Clara Valley Open Space Authority, spoke in favor of AB2509. Johnson claimed that only “small amounts of pesticide are used.” Landgraf said most plants are killed by grazing, mowing, and volunteers pulling my hand; herbicides are used only “when needed.”
Damon Connolly was the only committee member to speak. He expressed concern that AB2509 not conflict with his continuing support for AB99, which has the potential to reduce roadside spraying of herbicide by Cal Trans.
There were no speakers in opposition to AB2509. There was no acknowledgment of the public’s concern about AB2509 or of the public’s concern about herbicides being used on our public lands.
“What exists now can only ever come from what came before.” –Thomas Halliday, Otherlands
Otherlands, A Journey Through Earth’s Extinct Worlds was written by a paleontologist using the latest scientific techniques available. (1) Paleontology has advanced far beyond digging up fossils. Computer and DNA analysis enables paleontologists to reconstruct models of whole animals from bone fragments as well as describe the lifestyle of extinct animals such as what they ate and what ate them.
Geologic periods described by Otherlands. Source: Wikipedia
Thomas Halliday puts this knowledge of some of the 5 billion species that have gone extinct in the 4.6 billion years that Earth has existed into the context of geological and biological changes that caused their extinction. He describes vivid scenes of specific places at specific times, starting 500 million years ago (mya), a geological period when we can recognize most of the phyla (major groups of animals sharing characteristics) that exist today. These snapshots of deep time illustrate that “Environments shape their inhabitants as much as their inhabitants shape them.” (1)
In this article, we will visit a few of these scenes that demonstrate the biological innovations resulting from evolution and the associated geological and atmospheric events. And we will tell you about how modern conservation methods are often working at cross purposes against evolution and adaptation of life as it copes with catastrophic challenges.
Biological Innovation
Primitive life is said to have existed on Earth 3.7 billion years ago (bya). All life that presently exists on Earth is said to have evolved from the first life forms, although the common ancestor is yet to be identified. No life on Earth is truly alien.
The diversification of life on Earth began to accelerate when cyanobacteria developed the ability to photosynthesize about 3 bya. Photosynthesis converts sunlight to energy by consuming carbon dioxide, creating carbohydrates that feed plants and storing carbon in plants and the soil, while emitting oxygen into the atmosphere as a by-product.
This evolutionary innovation is responsible for the abundance and diversity of plants today. It is an important factor in the balance of carbon dioxide and oxygen in the atmosphere, which is one of the most important factors in the Earth’s climate. More plants also mean more food for animals that evolve alongside plants, often forming relationships with one another.
The first mass extinction, roughly 445 million years ago (mya), is the only mass extinction caused by a rapid change in the Earth’s climate from tropical to glacial, which is equivalent to saying the atmosphere changed from predominantly carbon dioxide to predominantly oxygen, the opposite of our currently changing atmosphere and climate.
Carbon dioxide levels are said to have dropped from 7,000 parts per million (ppm) to 4,400 ppm during the Ordovician extinction event that killed about 85% of plant and animal species. Currently our carbon dioxide level is about 420 ppm, just a fraction of what it was during the Ordovician period. In the context of the history of Earth, the climate we are experiencing is mild, a reminder of the potential for a much more extreme climate in the near future.
Comparing contemporary sea levels with those in deep time is another way to appreciate the potential for devastating changes in the future. 20,000 years ago, at the height of the last ice age, sea levels were 120 meters lower than they are now. Conversely, sea levels were highest during the mid-Silurian period, 430 mya, when sea levels were between 100-200 meters higher than they are now and atmospheric carbon dioxide concentrations were high.
Although the causes of the drastic change in the atmosphere and therefore the climate during the Ordovician period are still debated, the advent of photosynthesis is considered a factor. The development of fungi enabled plants to move from water to land by delivering moisture from soil to roots of plants, greatly increasing abundance and diversity of plants. About 80% of plants today receive much of their nutrients and moisture through mycorrhizal fungi.
The photosynthesizing capabilities of plants is one of the ways greenhouse gas emissions, currently causing global warming, can be reduced. Yet, we are using pesticides to kill plants that native plant advocates have arbitrarily decided “don’t belong.” Pesticides also kill fungi in the soil that enable plants to survive during drought conditions created by global warming. This is one of many examples of how management strategies used by humans are counteracting the accomplishments of evolution that occurred long before humans existed or began to think they were competent to “manage” nature.
Plant Evolution Timeline
To make a long, complicated story short, we’ll focus on the major plant groups we recognize today by starting with seedless land plants that reproduce by dispersing spores, such as mosses and ferns that evolved from algae about 460 mya.
Gymnosperms, which we recognize today as conifers, cycads, and Gingkos, are seed-producing plants that evolved about 300 mya. Early species of gymnosperms formed huge forests. The carbon they stored became the coal fields of today when they died during the Carboniferous period (360-300 mya). Today, we draw our fossil fuels from these coal and oil basins. They provide most of our energy, while releasing greenhouse gases causing climate change.
Continents were close together during the Cretaceous geologic period when angiosperms evolved. Source: Australian Museum
Angiosperms evolved from gymnosperms about 130 mya. They are flowering plants whose seeds are often encased in fruit. They are by far the most diverse group of land plants. The evolution of bees around the same time is an example of co-evolution: the flowers feed the bees and the bees pollinate the flowers, delivering pollen from the male anther to the female stigma. This sexual method of reproduction creates greater genetic diversity than self-pollination. Greater genetic diversity creates more opportunities for natural selection to operate on plant variations, which may result in species that are better adapted to existing conditions.
A recent study (2) found that the decline in the population of bees has increased the frequency of self-pollination of some plant species that are capable of both methods of pollination. This is an example of evolution at work today. Plants are responding to the existential need to reproduce in the absence of bees by self-pollinating.
What evolution has accomplished in the past can be undone. In this case, our indiscriminate use of pesticides such as neonicotinoids has decimated bee populations. Some plants will adapt to the loss of bees by self-pollinating, but not without some loss of genetic diversity provided by sexual reproduction and consequently the long term fitness of plants to face challenges in the future.
There’s another trade-off for both plants and bees. Producing nectar and attracting bees with colorful flowers is a big energy expense for plants. Plants therefore save energy by reducing flower size and color, when they can rely solely on self-pollination for reproduction. Obviously, self-pollination ultimately results in a loss of food for bees and may accelerate the decline in bee populations, a negative feed-back loop, if you will.
This example is a reminder that evolution is neither positive nor negative. It is simultaneously both positive and negative. It is what it is: an inexorable force for change.
Evolution of grasses
Grasses and grasslands are late comers to the Earth’s plant kingdom. Grasses evolved from angiosperms about 70 mya, during the Age of Dinosaurs that abruptly ended 66 mya when an enormous asteroid collided with Earth. Grasses are wind pollinated and their seeds are dispersed by the wind, which enables them to spread rapidly and widely.
Grasslands became dominant ecosystems about 30 mya, replacing many forest ecosystems. With the optimal combination of fuel, heat, and oxygen, wildfires were a factor in the transition from forests to grasslands in many places. Once again, wildfires in conifer forests are presently playing a role in converting forests to grasslands, suitable to a warmer and drier climate.
The development of enhanced photosynthesis by C4 grasses gave them a competitive advantage in hot, dry places where photosynthesis is suppressed. C4 grasses are more drought tolerant and they store more carbon than their predecessors, C3 grasses. There are only about 60 groups of C4 grasses, including several important food crops, such as maize, sugarcane, and sorghum. They are found in tropical and sub-tropical regions of Africa and South America and some deserts. California’s native grasses as well as introduced grasses considered “invasive” are not C4 grasses, according to a list of C4 grasses available on Wikipedia. (3)
Because of their potential to improve drought tolerance and increase productivity and carbon storage, there is great scientific interest in converting C3 grasses to C4 grasses. Despite decades of effort, agricultural science has not been able to duplicate what the natural forces of evolution have accomplished, reminding us that evolution is more powerful than we are.
The transition from forests to grasslands had a corresponding impact on the evolution of animals. Some browsers of woody plants learned to be grazers, if they could, while others went hungry, and the diversity and abundance of grazers increased.
Native plant advocates in California have selected grassland as their preferred ecosystem because it was the dominant ecosystem prior to the arrival of Europeans at the end of the 18th century. They have consistently failed to convert non-native grassland to native grassland in California. Nor is it clear that there would be any benefit to the environment or to its inhabitants to return to the treeless landscapes of California that existed prior to settlement in the late 18th century.
Where populations of native grazers of grassland were reduced by the activities of humans, many grasslands in California naturally succeeded to shrubs and trees. “Restoration” projects attempt to prevent succession of grasslands. Some of these projects destroy native trees and shrubs (e.g. Douglas fir, coyote brush, juniper, etc.) mechanically and with pesticides to maintain ecosystems as grassland.
Nativists also want to reintroduce the grazing animals of the pre-colonial period to replace domesticated animals humans introduced because nativists see them as competitors of native animals they consider superior. Where top predators have been killed, these herds of grazing animals outgrow available vegetation unless their numbers are controlled as domesticated animals are.
A recent meta-analysis of 221 studies of the impact of megafauna on plant abundance found, “no evidence that megafauna impacts were shaped by nativeness, “invasiveness,” “feralness,” coevolutionary history, or functional and phylogenetic novelty. Nor was there evidence that introduced megafauna facilitate introduced plants more than native megafauna. Instead, we found strong evidence that functional traits shaped megafauna impacts, with larger-bodied and bulk-feeding megafauna promoting plant diversity. Our work suggests that trait-based ecology provides better insight into interactions between megafauna and plants than do concepts of nativeness.” (4)
The author of Otherlands agrees that the concept of nativeness is not a useful way to understand the environment or conduct conservation because: “Where an animal or a plant from one part of the world appears in another, some might use the language of invasion, of a native ecosystem despoiled and rendered lesser by newcomers…In reality, species do move, and the notion of ‘native’ species is inevitably arbitrary, often tied to national identity…There is no such thing as a fixed ideal for an environment…To look into deep time is to see only an ever-changing list of inhabitants of one ecosystem or another…The concept of native that we so easily tie to a sense of place also applies to time…We must avoid putting our own ahistorical spin on what was, although certainly dangerous and unlikely, a journey guided entirely by chance.” (1)
Migration
The history of evolution is also a history of migration. The oscillation of the Earth’s climate between freezing cold and blistering heat created and destroyed land bridges that enabled or blocked migration as sea levels rose and fell. When North America and South America were connected by Central America as a result of lower sea levels and geological events about 3 mya, the plants and animals of those continents were mixed by migration. Likewise, aquatic life of the Pacific Ocean was separated from the Atlantic Ocean by the Central American land bridge until the Panama Canal was built in 1914.
Geological events also created or destroyed the same opportunities for migration. The opening and closing of the Strait of Gibraltar is a case in point. The Mediterranean Sea exists because the Strait of Gibraltar exists. When the narrow Strait is open, the Atlantic Ocean flows into the Mediterranean Basin, creating the Mediterranean Sea, which is an obstacle for migration of plants and animals between Europe and Africa.
About 6 mya the Strait of Gibraltar closed because the African tectonic plate moved north, colliding with the European tectonic plate. The Mediterranean Sea slowly evaporated, concentrating ocean salt from the Atlantic Ocean, laying down a sea bed of salt in the Mediterranean Basin and ultimately creating a migration corridor between Africa and Europe. There is every reason to believe that the Strait could close again. The Earth’s tectonic plates are in constant motion and there is no reason to believe they will stop moving.
The obsession with “where plants belong” seems to be based on ignorance of the history of dispersal and migration. Much of China and North America have been in the same latitude since the evolution of angiosperms. As a result, many of our plant species considered native in Eastern North America are also considered native in China. These paired species in the same genus are called disjuncts. There are many woody disjuncts in China and North America (magnolias, persimmons, hickory, catalpa, dogwood, sweetgum, tuliptree, tupelo, sassafras, Virginia creeper, etc) as well as many herbaceous disjuncts (ginseng, lopseed, mayapple, skunk cabbage, etc.). (5) They are different species because they have been separated long enough to change as a result of genetic drift, but are in the same plant lineage, therefore chemically similar and presumably used by the same insects. The study of these disjuncts says, “Most scientists do not consider long-distance dispersal to have played much of a role. The prevailing view is that most disjuncts are remnants of genera that were once widely distributed in the northern temperate zone during the Tertiary period [66 mya to 2.6 mya per Wikipedia]. These broad distributions in the northern hemisphere were made possible by recurring land bridges.” (5)
Lateral migration patterns of the past are changing in response to contemporary patterns of climate change. The temperatures at different latitudes are becoming more similar because Polar Regions are warming at a much faster pace than temperate and tropical latitudes. Plants and animals escaping extreme heat and associated changes in vegetation are moving to higher latitudes in the Northern Hemisphere and lower latitudes in the Southern Hemisphere. The increasing similarity of the Earth’s climate is changing wind and ocean currents and contributing to the extreme weather events of our changing climate. Although there are lessons in the events of deep time, we cannot assume that events in the past are entirely predictive of future events because of the complexity of natural processes and our limited understanding of them.
Of all the nonsensical conservation strategies humans are presently using, perhaps one of the most damaging is the futile attempt to stop migration. It is one of few survival strategies of plants and animals needed in a rapidly changing climate and it cannot be stopped.
The project that proposes to shoot barred owls in the Pacific Northwest is an example of a “conservation” project that does not deserve that honorific. Barred owls have migrated from the East to the West Coasts of North America via the boreal forests of Canada. This is another instance in which large contiguous stretches of land at the same latitude facilitate the migration of life because there is less variation in climate at the same latitude.
Source: USFWS
Specialists vs. Generalists
Barred owls are more adaptable than their closely related relative in the same genus, spotted owls. Barred owls have a more varied diet, they are willing to nest in less dense, second-growth forest, and they have greater reproductive success. They are therefore perceived as competitors of endangered spotted owls. Instead of letting natural selection identify the winner of that competition, the US Fish & Wildlife Service intends to shoot 500,000 barred owls in the next 30 years based on their belief that spotted owls will benefit. They do not expect to eradicate barred owls and they made a commitment to continue shooting barred owls in perpetuity. While we continue to log old-growth forests in which spotted owls live, we will kill barred owls with no expectation that they can be eradicated.
This project is typical of American “conservation” projects that attempt to save a specialist species by killing a generalist species. This strategy was enshrined in American law by the Endangered Species Act, which is now 50 years old. Like many 50-year-old public policies, we now know that this conservation strategy is not working because it is inconsistent with evolutionary principles. Change in nature is inexorable. Legal mandates are not capable of stopping evolution. If we had a functional political system, we could stop the greenhouse gas emissions causing climate change, but we don’t. Therefore, we must rely on evolution to cope with the changes in the environment that we have caused.
The most recent mass extinction occurred 66 mya when an asteroid hit the Earth, ending the Age of Dinosaurs. About 80% of all plant and animal species became extinct. The species that survived were the most versatile and the most mobile. Flying dinosaurs were the only dinosaurs that survived, as birds, perhaps because they were the most mobile. “Of the specialized insects, 85% were lost and it was the generalists that survived.” (1)
Mass extinctions have created many vacant ecological niches that are opportunities for experimentation, creating new species. Some were better adapted than others. Natural selection determined the winners of competition within ecological niches. The end of the Age of Dinosaurs created the opportunity for the Age of Mammals, as well as bony fish, marsupials, and lizards.
In other words, our outdated conservation strategy is wasting our limited resources to save specialized species that are probably doomed to extinction. And we are doing so at the expense of generalist species that might survive if we would quit killing them. Keep in mind that 99% of all life forms that have existed on Earth have gone extinct. At a time when the climate is changing rapidly, the goal of saving every endangered species seems both unrealistic and wasteful of limited conservation resources.
Hybridization
Hybridization is one of the tools of evolution. Closely related species, usually in the same genus and even family often mate and their offspring often survive to eventually give rise to new species. Successful hybridization is a means of increasing biodiversity. Hybridization is sometimes a means of improving adaptability and therefore survival.
Unfortunately, nativists see hybridization as a loss of biodiversity rather than an opportunity to improve adaptability and increase biodiversity. Their “conservation” projects often attempt to prevent hybridization by killing hybrids. For example, the plan to kill 500,000 barred owls includes all hybrids of barred and spotted owls. Because barred owls are more versatile, hybridization with spotted owls could even the playing field with barred owls by expanding food sources and nesting habitats of spotted owls.
The Spartina eradication project is another example of the pointless eradication of hybrids. In the case of Spartina, the non-native species grows more densely and it doesn’t die back in winter. Non-native Spartina provides better storm protection and better habitat for nesting birds. The Invasive Spartina Project has been spraying hybrid Spartina with herbicides for over 20 years, without total success. The hybrid looks so similar to native Spartina that hundreds of genetic tests are required to confirm their identification as hybrids before they are sprayed. The Invasive Spartina Project is a waste of limited conservation resources and it serves no useful purpose.
Evolution vs. Conservation
Otherlands should be required reading for those who are engaged in the “restoration” industry. Some of the methods and goals of conservation are at odds with the mechanisms of evolution that have ensured the survival of life on Earth for nearly 4 billion years.
The use of pesticides by “restoration” projects is antithetical to the goal of conservation because they do more harm than good.
Migration is a means of species survival. Natural migration of plants and animals cannot and should not be stopped.
Humans cannot duplicate the forces of evolution. Natural selection is the most powerful, efficient, and effective method of determining the winners of competition.
Hybridization has the potential to improve adaptability of closely related plants and animals. Hybridization cannot and should not be stopped.
Resources being wasted in the attempt to stop the natural forces of evolution should be redirected to reducing greenhouse gas emissions causing climate change. Such efforts are appropriately called “conservation.”
Thomas Halliday, Otherlands, A Journey Through Earth’s Extinct Worlds, Random House, 2023
Erik Lundgren et.al., “Functional traits—not nativeness-shape the effects of large mammalian herbivores on plant communities,” Science, February 2, 2024
David Yih, “Land Bridge Travels of the Tertiary: The Eastern Asian-Eastern North American Floristic Disjunction, Arnoldia, 2012
The Endangered Species Act requires that the Environmental Protection Agency (EPA) conduct biological evaluations (BE) of the impact of pesticides on threatened and endangered species protected by the ESA. For example, when the EPA published its final evaluation of glyphosate in 2021, it informed us that glyphosate is “likely to adversely affect” 93% of legally protected endangered and threatened plants and animals.
Source: EPA Biological Evaluation for Glyphosate
The EPA published a draftof a biologicalevaluation (BE) of 11 rodenticides in November 2023, which is a free gift to the island eradication industry. The deadline for making comment on this draft is February 13, 2024. Public comment can be made HERE.
The EPA’s biological evaluation for rodenticides reached the conclusion that rodenticides used in island eradications have “no effect” on any aquatic plant or animal, including birds in the aquatic food web and amphibians with a fully aquatic lifestyle. They made this “no effect” determination without evaluating any of those species, based on their claim that the Product Label for the rodenticide used in island eradications prohibits its use in water, which is not true. EPA also extended this “no effect” determination to all species under the jurisdiction of National Marine Fisheries Services. (1)
In fact, the standard Product Label for brodifacoum does not explicitly prohibit the use of the product in water. It merely warns of the deadly consequences for aquatic species if used in water: “This product is extremely toxic to birds, mammals, and aquatic organisms. Predatory and scavenging mammals and birds might be poisoned if they feed upon animals that have eaten bait. Runoff may be hazardous to aquatic organisms in water adjacent to treated areas. DO NOT contaminate water when disposing of equipment wash water or rinsafe.” The standard Product Label also explicitly allows aerial broadcast of rodenticides for island eradications.(2) In other words, it’s dangerous to apply rodenticides to water, but, in fact, it often happens during island eradications. The biological evaluation asks the public to believe the EPA’s claim that rodenticides are not used in water despite ample evidence that rodenticides land in water during aerial broadcasts on islands.
Although the standard Product Label acknowledges the potential that rodenticide runoff “may be hazardous to aquatic organisms in water adjacent to treated areas,” EPA’s biological evaluation dismisses that possibility by claiming that “use patterns preclude spray drift and runoff exposure.” EPA’s biological evaluation provides no evidence in support of that claim and that claim is explicitly contradicted by the EPA in its evaluation of the proposed island eradication on the Farallon Islands as well as the considerable record of contamination of the aquatic food web during completed island eradications, as explained below.
Supplemental Product Labels are required for island eradications because they require greater quantities of rodenticide bait than allowed by standard Product Labels and modifications in application methods. The Supplemental Product Label required for island eradications explicitly permits the use of brodifacoum on water (3):
Elevated and floating bait stations are allowed in intertidal zones above the mean low tide mark and below the mean high tide water mark.
Broadcast applications are allowed in coastal areas above the mean high tide water mark. Conversely broadcast applications are prohibited below the mean high tide water mark.
The cited Supplemental Product Label for Wake Island was recently published in preparation for a second attempt to eradicate rats on Wake and 2 adjacent islands. The first attempt in 2012 was a failure. Here is a photo of this complex of islands:
Wake Island. Source: NASA
As you can see, Wake Island is a narrow strip of land surrounding a lagoon that is open to the ocean. Two-thirds of the island is surrounded by sandy, tidal beaches. Scrub vegetation is in the intertidal zone. A portion of the island’s vegetation is wetland. It defies belief that it is possible to aerial broadcast rodenticide from helicopters (or float bait boxes in the intertidal zone) on Wake Island without getting rodenticide in the water.
The published study about the failure of the first attempt to eradicate rats on Wake Island was written by the organizations that conducted the project. It reports that rats were found on the island less than a year after the aerial broadcast and supplemental hand-applications were done. The study makes no mention of non-target deaths of any animals. The study speculates that the failure of the attempt was the result of not applying the rodenticide everywhere rats were living. They will soon try again, using the same methods. Rodenticide bait will surely end up in the water. More non-target animals will undoubtedly be killed. But the public will not learn about either of those issues, because the monitoring and reporting is entirely controlled by the perpetrators of these projects. (4)
Keep in mind that there are 239 taxa living in the intertidal zone around the Farallon Islands, according to Appendix J of the Final Draft of the Environmental Impact Statement for the proposed Farallon Islands. No Supplemental Product Label has been granted yet for the proposed island eradication on the Farallon Islands, but the Farallones are included on the list of 29 island eradications (below) in the EPA’s biological evaluation, which the BE says will be done within the next 5-7 years.
Source: EPA Biological Evaluation of Rodenticides
Contamination of the aquatic food web during island eradications is inevitable
EPA made a public record of its concerns about contaminating the aquatic food web during island eradications in its letter of December 9, 2013 regarding “EPA comments on the Revised Draft Environmental Impact Statement for the South Farallon Islands Invasive House Mouse Eradication Project.” (5) In response to the claims of the DEIS for the proposed island eradication that “the bait deflector will minimize, and in several places, prevent bait drift into the marine environment,” the EPA said, “The EIS should be clear that bait drift would occur.”
The EPA’s letter of December 9, 2013, goes on to report previous experience with aerial broadcast applications on Palmyra Island and states: “For future operations, the potential for bait to enter the marine environment must be a factor in the aquatic risk assessment and further methods to minimize the amount of bait entering the marine environment should be fully explored. The amount of bait that enters the aquatic environment from an aerial broadcast depends on shoreline configuration, island topography, overhanging vegetation, bird activity affecting flight lines, wind strength and direction, weather conditions, and pilot experience. On islands where these factors increase the potential for bait to enter marine environments, additional mitigation measures may be needed to protect sensitive marine environments.” (5)
Based on those concerns about contamination of the marine food web, the EPA’s letter of December 9, 2013 expresses these specific concerns about the proposed aerial broadcast application on the Farallon Islands: “Discuss and consider the factors that increase the potential for bait to enter marine environments that are identified above. Especially relevant are the irregular shoreline, the excessive bird activity from gulls, and the proposal to fly steep areas a second time (shorelines on the Farallones are steep) to increase the application rate in these areas.” (5)
Given the EPA’s explicit admission that aerial broadcast of rodenticides on islands have contaminated the marine food web in the past and are likely to do so in the future, the EPA is not in a position to now categorically deny that “use patterns preclude spray drift and runoff exposure,” as it attempts to do in the draft biological evaluation. Nor is the EPA in a position to categorically deny that aquatic species will be adversely affected by rodenticide bait that will inevitably land in the water surrounding the Farallon Islands, as it attempts to do in the draft biological evaluation.
Farallon Islands, NOAA
The deadly track record of island eradications
The aerial application of rodenticide to kill rats on Anacapa Island in 2001-2002 was the first of its kind in North America. The project was complicated by the need to spare a population of endemic native mice on Anacapa. Over 1,000 native mice were captured before the aerial application of rodenticide and released back on the island after the poison was no longer effective. Clearly, mice aren’t considered a problem on islands, unless they have the bad luck of being non-native. Whether native or non-native, they are prey for many bird species.
Most of the raptors on Anacapa were removed before the rodenticide drop. Of those that were left behind, 3 barn owls, 6 burrowing owls, and a kestrel likely died from rodenticide bait or eating poisoned mice. 94 seed-eating birds were also found dead after the poison drop. The study says that these collateral kills were consistent with other similar projects.
Bird scavengers such as gulls, vultures, and condors are also vulnerable to secondary poisoning by poisoned rodents. Shortly after the Anacapa poison drop, dead seabirds washed up on the shore near the Santa Barbara harbor. UC Santa Barbara’s daily newspaper said, “…a strong correlation exists between the National Park Service’s most recent airdrop of pesticide on Anacapa Island and the dead birds.” These deaths weren’t reported by the study of the success of the poison drop. As usual, the study was done by supporters of the project, with little interest in finding more collateral death from the drop. The public is not allowed to observe island eradications. Therefore, the public’s only source of information is those who are directly involved in the aerial application of rodenticides.
“In October 2008, two helicopters dropped approximately 46 metric tons of Brodifacoum 25-W bait on Rat Island’s 2800 hectares, supplemented by hand application of bait around the island’s freshwater lakes. This rodenticide is known to be highly toxic to birds. Some nontarget mortality was expected, but the actual mortality exceeded the predicted mortality. Forty six Bald Eagles died (exceeding the known population of 22 Bald Eagles on the island); toxicological analysis revealed lethal levels of brodifacoum in 12 of the sixteen carcasses tested. Of the 320 Glaucous winged Gull carcasses, toxicology tests implicated brodifacoum in 24 of the 34 tested. Carcasses of another 25 bird species were found; of these 54 individuals, three were determined by necropsy to have died of brodifacoum poisoning.” (6)
Palmyra Atoll was aerially broadcasted twice with brodifacoum rodenticide in 2011 as well as a follow-up hand broadcast application. The study of that project reported: “We documented brodifacoum residues in soil, water, and biota, and documented mortality of non-target organisms. Some bait (14–19% of the target application rate) entered the marine environment to distances 7 m from theshore. After the application commenced, carcasses of 84 animals representing 15 species of birds, fish, reptiles and invertebrates were collected opportunistically as potential non-target mortalities. In addition, fish, reptiles, and invertebrates were systematically collected for residue analysis. Brodifacoum residues were detected in most (84.3%) of the animal samples analyzed. Although detection of residues in samples was anticipated, the extent and concentrations in many parts of the food web were greater than expected.”
These published studies are helpful to understand the scale of water contamination and collateral deaths of non-target animals, including aquatic animals. However, they are just the tip of the toxic iceberg because little monitoring and testing is done on the many marine animals that have been killed in proximity of these projects. Robert Boesch is a retired pesticide regulator for the EPA and the Hawaii Department of Agriculture. Presently, he is Visiting Colleague at University of Hawaii at Manoa. He has written an unpublished discussion paper (7) that reports:
Strandings of whales, some hemorrhaging, occurred within 60 days following anticoagulant bombardment.
Unusual mass strandings of hemorrhaging dolphins occurred in San Diego and Hawaii years after anticoagulant bombardment.
There is very little known about the fate of anticoagulant residues in the oceans.
Source: Robert Boesch discussion paper available HERE .
The documented deaths of non-target animals caused by island eradications are direct poisonings by eating bait on the ground or by secondary poisoning by eating poisoned rodents. The EPA biological evaluation attempts to dismiss the potential for secondary poisonings by citing a study (Baldwin 2021) that claims most rodents die in their burrows after eating the poison, making them unavailable to be eaten by other animals. This study is not relevant to island eradications because it was conducted on ground squirrels (not rats or mice), it used a first generation rodenticide (diaphacinone) which is not used in island eradications, and most applications were burrow baits, rather than aerial broadcast.
What’s at stake?
About 1,200 island eradications have been done all over the world over the last 30 years, with mixed success. The EPA’s biological evaluation announces the intention to approve 29 new island eradications in US waters within the next 5-7 years, including the Farallones. In the case of Hawaii, the list says “all islands.” Many of the listed islands are actually a complex of islands, such as those in Boston Harbor. Many of the islands are residential communities, such as Nantucket and Martha’s Vineyard. As presently drafted, the biological evaluation will make it possible to approve those projects without addressing the considerable evidence that these projects are killing thousands of birds and animals and contaminating the ocean surrounding island eradications.
The Bottom Line
The draft biological evaluation is unacceptable because it gives the public the false impression that island eradications with rodenticides are harmless, when they clearly are not. It confers EPA’s blessing on island eradications by refusing to evaluate endangered species that may be harmed by island eradications. It ignores the evidence that rodenticide applications have killed many terrestrial and aquatic animals and contaminated the water.
The biological evaluation must be revised to correct these flaws in the present draft:
Exposure to rodenticides during island eradications must be based on Supplemental Product Labels for island eradications, not standard Product Labels that do not apply to island eradications.
The revised biological evaluation must evaluate all legally protected animals exposed to rodenticides during island eradications, including aquatic animals. Both bioconcentration and bioaccumulation must be considered in the determination of exposure to rodenticides. “No effect” cannot be assumed without such evaluation.
The revision must provide evidence in support of the claim that there is no drift or run-off of pesticide from aerial broadcasts done on islands or delete that claim, which is contradicted by actual experience with island eradications.
The revision must remove the claim that rodents die in their burrows after eating rodenticide bait (Baldwin 2021) because the study was done on a different animal, using a different rodenticide, and a different application method.
“The more we know about plans to eradicate harmless mice on the Farallon Islands with rodenticide, the less sense it makes.” – Conservation Sense and Nonsense
Plans to eradicate mice on the Farallon Islands with rodenticide were approved by the California Coastal Commission (CCC) two years ago, on December 16, 2021. Although CCC approval was contingent on a few conditions intended to reduce the inevitable death of non-target birds and marine animals, it is unclear if CCC will be able to enforce the conditions. Plans seem to be moving forward behind closed doors, so Conservation Sense and Nonsense continues to be concerned about this project.
First a brief reminder of the project and our objections to it. House mice were introduced to the Farallon Islands over 100 years ago by ships visiting the island. There is no evidence that mice harm birds on the Farallons. The mice are an integral part of the food web, eating primarily vegetation and supplementing that diet with insects during summer months when vegetation is sparse. The mice are also the prey of hundreds of thousands of birds that live on the islands as well as birds that stop over on their migratory routes. The mouse population varies throughout the year, dwindling during winter months and increasing in the fall. When the mouse population declines, food sources for their predators also decline. That’s when burrowing owls are said to prey on the nestlings of ashy storm petrels. Though the mice are blameless, the project proposes to kill them all based on the assumption that burrowing owls will not overstay their migratory stop over if food sources are significantly reduced. The project is expected to kill hundreds—perhaps thousands—of non-target birds who will eat poisoned pellets directly and/or poisoned mice.
The project has always seemed absurd and nothing we’ve learned about it in the past 2 years has made it seem otherwise. Our last article of 2023 will report new information learned since the project was approved.
Contamination of the food web
Robert Boesch is a retired Pesticide Regulator for the Environmental Protection Agency, region 9 and the Hawaii Department of Agriculture. Presently, he is Visiting Colleague at University of Hawaii at Manoa. Based on his research and experience, he has written a discussion paper about island eradications using rodenticides, which he has shared with the California Coastal Commission and many other agencies and organizations. This entire discussion document is available below as a footnote and this is his summary of “Eradication Programs Eliminating Invasives and their Predators and Scavengers!”
Eradication programs for mice and Polynesian Rats are planned for the Farallon Islands, Midway and Wake Island.
Brodifacoum, a potent, persistent and bioaccumulative anticoagulant poison is the toxicant. [This is the rodenticide that will be used on the Farallon Islands to kill mice. There are no rats on the Farallons.]
Brodifacoum residues have been detected in almost all fish that were collected following treatment of Palmyra, and trace levels were found in 10 percent of the fish after treatment of Wake.
Brodifacoum residues in fish caught at Wake increased from trace levels to detectable residues over 3 years.
Diphacinone is a greater threat of secondary poisoning to mammals than brodifacoum.
Strandings of whales, some hemorrhaging, occurred within 60 days following anticoagulant bombardment.
Unusual mass strandings of hemorrhaging dolphins occurred in San Diego and Hawaii years after anticoagulant bombardment.
There is very little known about the fate of anticoagulant residues in the oceans.
Our knowledge of contamination of the food web caused by rodenticide drops on islands is limited because monitoring is usually short-term and frequently done by the same contractors who implemented the project, with little motivation to report the extent or persistence of contamination. For the same reasons, we have limited knowledge of how successful the projects are.
Track record of island eradications
About 1,200 island eradications have been done all over the world over the last 30 years. Our evaluation of the proposed project on the Farallon Islands is based on the success or failure of those projects.
The aerial application of rodenticide to kill rats on Anacapa Island in 2001-2002 was the first of its kind in North America. The project was also unique because it was complicated by the need to spare a population of endemic native deer mice on Anacapa. Over 1,000 native mice were captured before the aerial application of rodenticide and released back on the island after the poison was no longer effective. Although post-project monitoring reported successful eradication of rats, they were not confident that all of the mice that were left on the island had been killed. (1)
Attempts to eradicate mice have been consistently less successful than attempts to eradicate rats. A study of 139 attempted eradications of animals on 107 Mediterranean islands in eight countries found that eradication projects targeted 13 mammal species. The black rat was the target of over 75% of the known attempted eradications in the Mediterranean Basin. The most widely used technique was poisoning (77% of all eradications), followed by trapping (15%) and hunting (4%). Techniques were largely target-specific.
The average failure rate of the projects was about 11%, but success was defined only as the death of animals living on the islands at the time of the project. However, this percentage varied according to species. The failure rate of house mouse eradication was 75%. Reinvasion occurred after 15% of eradications initially considered successful. (2)
Island eradications considered initially successful, are often failures in the long run. A recent visitor to Anacapa Island has reported seeing two dead rodents as her escorted group was leaving the island. One was identified as a deer mouse. The other rodent was not identified. Have rats returned to Anacapa? Are native deer mice still being killed by residues of rodenticide? (3)
The eradication of rats on Anacapa Island is relevant to the planned project on the Farallon Islands because rats were killed, but mice were saved. Although the Anacapa project considered rats a threat to birds, it did not consider mice a problem. Rats were killed, but mice were saved by trapping and removing them from the island before the rodenticide was dropped. Mice on the Farallon Islands are not a threat to birds. They will be killed only because they are non-native.
Mice are members of the food web
Mice on the Farallon Islands are as much a part of the food web as they are on Anacapa Island. They are prey of the birds and they are mainly predators of vegetation. On the Farallon Islands, mouse predation of vegetation is considered a problem, but on Anacapa Island it is not considered a problem. On the Farallon Islands, the study of the diet of mice reports that mice also eat insects when vegetation becomes scarce in the fall. (4)
The study of the mouse diet on the Farallons also reports that 63%-80% of the vegetation on the Farallons is non-native. That’s why Roundup (glyphosate)has been used on the Farallon Islands every year since 1988. Between 2001-2005, an average of 226 gallons of herbicide were used annually (5.4 gallons per acre per year), according to the annual report of the Farallon National Wildlife Refuge. (5)
I took this photo on Santa Cruz Island in 2010, while visiting with an escorted group.
The Farallon Islands have never been inhabited and there has been no public access to the islands for over 100 years. Non-native plants were not brought to the Farallons by humans. Their seeds were brought by birds in their stomachs, in their feathers, on their feet and by wind and ocean currents. Non-native plants dominate vegetation on the Farallons partly because non-native plants are eaten by birds. The plants are members of the food web and their eradication is depriving birds and other animals in the ecosystem of food. If non-native plants were not being eradicated with herbicides, it probably would not be necessary for mice to eat insects, which are not their preferred food. We can safely assume that herbicides are harmful to the animals that consume plants that have been sprayed. (6)
Consequences of fiddling with the food web
There were also feral cats on the Farallons before they were killed. Predictably, the population of mice increased after the cats were killed. When 6,000 feral pigs were killed by sharp shooters on Santa Cruz Island, Golden Eagles substituted for that plentiful food source by preying on the rare, native Channel Island Fox. Golden Eagles were captured and relocated to the mainland. The fox population was restored to the island by a captive breeding problem. The same could be done on the Farallons to eliminate the only known threat to ashy storm petrels. The small population (approximately 6-10) of burrowing owls that are the only known predators of the petrels could be trapped and removed to the mainland as the Golden Eagles were on Santa Cruz Island.
Restoration plans for any ecosystem should begin with a thorough analysis of the food web. Plucking single species of plants and animals out of complex ecosystems without understanding their role in the food web results in unintended and harmful consequences.
The Farallons project is based on mistaken assumptions
The Farallons project is based on the mistaken assumptions of invasion biology. Most of the vegetation on the island is being killed with herbicide because it is non-native. The vegetation is clearly essential to all the animals living on the island, but invasion biology asks us to believe that it is not, solely because it is non-native. If the mice are killed on the island, it is only because they are non-native, not because they are harmful to birds. They are an important source of food for the birds, but invasion biology asks us to believe they are not, solely because they are not native. These assumptions are wrong, yet 50 years of nativist ideology still has a death grip on our public lands.
This deadly dogma is losing its grip, but apparently too slowly to prevent the destruction of the food web on the Farallon Islands. I always attend the conferences of the California Invasive Plant Council (Cal-IPC) and the California Native Plant Society (CNPS) to give native plant advocates every opportunity to convince me of their ideology. Consistently, I find more support for my contrarian viewpoint than I do for invasion biology. A presentation about the salt marsh harvest mouse at the Cal-IPC conference in October 2023, is an example.
California Department of Fish and Wildlife collaborated with UC Davis to study the food preferences of salt marsh harvest mouse (SMHM), an endangered native animal that lives in the wetlands of the San Francisco Bay. It has always been presumed to be entirely dependent on native pickleweed for food and habitat. The legally mandated recovery plan is based on that mistaken assumption.
Presentation to California Invasive Plant Council conference in October 2023
The study reported to Cal-IPC shows clearly that SMHM is NOT dependent on pickleweed for either food or habitat. SMHM is an extreme omnivore. SMHM ate 39 species of native and non-native plants as well as insects in empirical trials. In fact, it ate EVERY plant it was offered. A fecal study of SMHM living in the wild confirmed that finding. Fecal analysis found SMHM had eaten 48 native and non-native plant genera as well as some insects.
Presentation to California Invasive Plant Council conference in October 2023
SMHM have no preference for native plants for either food or nesting habitat. The most SMHM’s captured in the study were found where there was less than 10% pickleweed.
This was an absurdly simple experiment in which SMHM were captured and fed a variety of plants. It could have been done by anyone with little knowledge or fancy equipment. Why does this foolish mistake, caused by nativist bias, matter? Because “restoration” projects all around the San Francisco Bay have been eradicating non-native plants, claiming it would benefit the endangered SMHM.
Nativism in the natural world is not benefiting wildlife. Rather it seems to benefit only the army of “restorationists” who earn their living killing harmless plants and animals. As long as they continue to receive public funding for their projects, they have job security because they have spent over 20 years trying to do something that cannot be done. Evolution moves inexorably forward. The puny efforts of humans to regress landscapes to arbitrarily selected historical standards cannot change the forward trajectory.
There were two presentations about difficulties with native plant restorations on Anacapa and Santa Rosa Islands at the CNPS conference in October 2022. More than 20 years after non-native iceplant, rabbits, and rats were killed on Anacapa, native flora and fauna are still described as degraded, “Due to the cumulative and severe impacts to the soil and native seedbank, native vegetation communities have not recovered on their own…” On Santa Rosa Island the “restoration” community has installed artificial fog fences to replicate a historical cloud forest to improve survival of native chaparral plants. (7)
Alternatives to rodenticide drop on Farallon Islands
It is not necessary to kill mice on the Farallon Islands because they are not harmful to birds. If non-native vegetation weren’t killed with herbicides, there would probably be enough vegetation for omnivorous house mice as well as birds. Both mice and vegetation are being killed only because they are non-native. If the nativist ideology were removed from the agenda, dumping rodenticides on mice and herbicides on non-native vegetation would not be necessary.
If the protection of ashy storm petrels really were the goal of the proposed project on the Farallon Islands, the most obvious solution would be to remove the small population of burrowing owls that are the only known predators of the petrels. Keep in mind that ashy storm petrels are not considered threatened or endangered and that two applications for protected status have been denied. (8)
There is a non-lethal alternative to reducing populations of rodents using rodenticides that kill non-target birds and other animals. Academic scientists at Arizona State University have developed birth control for rodents that can be used on the Farallons to reduce the population of mice. (WISDOM Good Works)
In Summary
Killing house mice on the Farallon Islands with rodenticide is unnecessary and will be harmful to the ecosystem and its inhabitants because:
Aerial dropping 1.5 tons of rodenticide will poison the entire ecosystem, killing hundreds of non-target birds and marine animals.
House mice on the Farallon Islands do not need to be killed because they are food for birds and they are harmless.
If burrowing owls are killing nestlings of ashy storm petrels, they could be removed and relocated.
The nearly 40-year attempt to kill non-native vegetation with herbicide should be stopped because the vegetation is a vital element in the food web of the Farallon Islands.
In June 2023, Washington Post published an opinion piece advocating for the use of herbicides to kill non-native plants, in which Doug Tallamy was quoted as saying that spraying herbicide on non-native plants is “chemotherapy,” equating non-native plants with cancer and pesticides with medical therapy. Tallamy. and more broadly his viewpoint, received some blowback from Conservation Sense and Nonsense and others.
Thomas Christopher and Doug Tallamy collaborate on their shared mission of promoting the use of native plants and the closely related goal of eradicating non-native plants they consider a threat to native plants and insects. In October 2023, Tom Christopher (TC) gave Doug Tallamy (DT) an opportunity to respond to criticism of native plant dogma on his Growing Greener podcast that is available HERE. Christopher also invited listeners to send him feedback on the podcast. Professor Art Shapiro, whose work was central to the interview, has responded separately and his response is available as a footnote. Conservation Sense and Nonsense (CSN) sent Christopher an email, which I hope he shared with Tallamy. The following is an excerpt from that email.
Hi Tom, Thanks for the air time for opposition to eradicating non-native plants in your interview with Doug Tallamy and for this opportunity to respond. I’m flattered that criticism of native plant dogma has attracted some attention on the East Coast. I’ve transcribed most of your interview with Doug Tallamy as best I can and provided some feedback to Tallamy’s viewpoint. I sent Art Shapiro the podcast and he has responded separately.
TC: Some people say that non-native plants are just as effective as natives in supporting food webs. For example, buddleia that is spreading throughout the East and West is used by butterflies.
CSN: Buddleia davidii is on California’s list of invasive plants, but it is not considered invasive in California. It was put on California’s list because it is considered invasive elsewhere, making the point that invasive plant behavior varies depending on local conditions, such as climate. Sweeping generalizations about invasiveness are rarely accurate. If gardeners are concerned about the potential for invasive behavior, they can plant a cultivar of buddleia that does not reproduce.
DT: We shouldn’t call all insects pollinators. Just because an insect visits a flower for nectar doesn’t mean it’s pollinating that flower. There are more visitors to flowers than there are pollinators. Butterflies visiting buddleia are just there to sip nectar.
Variable checkerspot. Photo by Roger Hall
CSN: Buddleia davidii is native to Central China. Non-native buddleia is used by a butterfly species that is native to California and other states in the Western US.
The first actual observation of checkerspot butterflies breeding spontaneously and successfully on buddleia was in Mariposa County, California in the Sierra Nevada foothills. Checkerspot bred there successfully on buddleia in 2005 and in subsequent years. This colony of checkerspot on buddleia was reported in 2009: “We conclude that buddleia davidii [and other species of buddleia] represents yet another exotic plant adopted as a larval host by a native California butterfly and that other members of the genus may also be used as the opportunity arises.” (1)
In 2017, a gardener in Mendocino County, California also reported the use of buddleia as the host plant of checkerspot: “By now I am questioning how it was that butterfly larvae were using my butterfly bush as a host plant, completely against everything I’d ever heard. How was this possible? I emailed Art Shapiro, a very well-known butterfly expert and author, sending him a pic. He wrote back to confirm they were butterfly larvae, but added, ‘These are not mourning cloak butterflies. They are checkerspots. And the only time I’m aware this has happened [like, ever, except one in a lab in 1940…] is in Mariposa County.’” (2)
Buddleia is available as the host plant of checkerspot butterflies with a native range from Alaska south along the Pacific Coast through California and Arizona to Baja California and Mexico; east to Montana, the Dakotas, Wyoming, Colorado, New Mexico. This is a clear case of a widespread native butterfly choosing a non-native plant as its host.
Arthur M. Shapiro and Katie Hertfelder, “Use of Buddleia as Host Plant by Euphydryas chalcedona in the Sierra Nevada foothills, California,” News of the Lepidopterists’ Society, Spring 2009
DT: Most bees that people see in their gardens are honeybees that are there to get pollen and sometimes nectar. These are generalist bees but specialist bees that require pollen from particular plants (always native plants) can’t be supported by those at all.
Squash bee. USDA public domain
CSN: Specialization of insects is exaggerated by Tallamy. For example, he would probably call a squash bee a specialist. As its name implies, its host plant is squash plants in the squash family, with 98 genera and 975 species. The squash bee is considered an excellent pollinator of zucchini and butternut squash, both native to Central and South America. However, they do not usually visit melon plants, according to Wikipedia. Again, we are reminded to avoid broad generalizations when describing the complex and diverse natural world.
Likewise, the native alkali bee is a particularly effective pollinator of alfalfa, which is native to the Mediterranean region. Alkali bees also pollinate members of the large legume family with over 16,000 species that are native all over the world. If you are interested in such associations, you can find an exhaustive list of native butterflies and their many non-native host plants in Art Shapiro’s butterfly guide for Central California and the Bay Area. It is not true that bees Tallamy considers “specialists” require pollen from only native plants.
DT: Sometimes butterflies adopt a new host plant as a caterpillar host. For example, black swallowtail butterflies caterpillars eat carrots or parsley or dill. What’s going on? There are two different kind of hosts: 1) The caterpillar has not adopted a new host at all because it was already adapted to that particular host. 2) Actual host switching from one plant to another is very rare. It happens on a time-scale of thousands of years. It requires a mutation or an adaptation to chemical defenses of new host plants.
CSN: Tallamy tries to make a distinction to avoid acknowledging that insects make use of introduced plants because they are chemically similar to the native plants they have used in the past, which in some cases are no longer available. The butterfly has, in fact, adopted a new host, a plant that wasn’t there before and is now hosting the caterpillar. There are many cases of rapid evolution that enable such transitions, but both cases are clearly transitions from native to non-native plants. If the original native host is still available, it isn’t necessarily abandoned in favor of a non-native. Such transitions are useful because they increase the population of available insect hosts and are essential if the original native host is no longer available.
TC: Pushback from California cites research of Professor Art Shapiro reporting that spontaneous spread of non-native plants has benefited native butterflies. He reports that 82 of 236 California native butterfly species (34%) are laying their eggs on introduced plant taxa, so caterpillars feed on them and many more butterflies use introduced plants as nectary sources.
DT: Great! These are host range expansions. Agriculture in California has eliminated the host plants of a lot of butterflies and it’s a good thing we had close relatives of natives so butterflies could expand their host range and use them. But if 34% of native butterflies are using introduced plants that means 66% are not. If all plants were introduced, we would lose 66% of butterflies in California. This is not the direction I want to go. I would choose 60% rather than 34%.
CSN: Christopher and Tallamy seem to have read one sentence in the abstract of Shapiro’s study without reading subsequent sentences: “Interactions with introduced plant taxa are not distributed evenly among butterfly species. Alpine and desert butterflies interact with relatively few introduced plants because few exotic plant species have reached and successfully colonized these habitats. Other California butterfly species are specialists on particular plant families or genera with no exotic representatives in California and have thus far failed to recognize any introduced plants as potential foodplants. Some California butterflies have expanded their geographic ranges and/or extended their flight seasons by feeding on exotic plants.” In other words, where there are more introduced plants and some are closely related to native plant hosts, more native butterflies use introduced plants.
TC: What do you say to the claims that introduced plants stay greener longer than native plants adapted to wet or dry seasons so that introduced plants give rise to extra generations of caterpillars?
DT: This is only true if caterpillars can use those plants and in host range expansions they can. Shapiro is also right about extending availability of nectar. For example, monarchs that migrate need forage along the way. The minus is that we’ve been so hard on native flora. These insects were doing just fine before we brought in non-native plants. It’s a Band-Aid we’re putting on an environment that has been ravaged by taking out native species that were here before. Let’s put native species back too.
CSN: The claim that non-native plants are driving native plants to extirpation or extinction goes to the heart of the controversy. Native plant advocates believe that accusation, although there is little evidence to support it. The greatest threat to native plants and insects is habitat loss, particularly converting wildlands to agricultural fields. The second greatest threat is the pesticides that are used by agriculture. Remember that Tallamy is an enthusiastic promoter of herbicides to eradicate non-native plants. He calls it “chemotherapy” in a recent opinion column in the Washington Post. Pesticides kill both plants and the animals that feed on them, they are anathema to biodiversity and the food web that Tallamy believes he is supporting.
Marcel Rejmanek (UC Davis) is the author of the most recent report on plant extinctions in California, published in 2017. At that time there were 13 plant species and 17 sub-species native to California known to be globally extinct and another 30 species and sub-species extirpated in California but still found in other states. Over half the globally extinct taxa were reported as extinct over 100 years ago. Although grassland in California had been converted to Mediterranean annual grasses by grazing domesticated animals decades before then, most of the plants now designated as “invasive” in California were not widespread over 100 years ago.
Most of the globally extinct plant species had very small ranges and small populations. The smaller the population, the greater the chances of extinction. Most of the globally extinct plants were originally present in lowlands where most of the human population and habitat destruction are concentrated. Although there are many rare plants at higher altitudes, few are extinct. Plants limited to special habitats, like wetlands, seem to be more vulnerable to extinction. The primary drivers of plant extinction in California are agriculture, urbanization and development in general. Non-native plants are the innocent bystanders to disturbance.
“Invasive species” are mentioned only once in the inventory of extinct plants published by California Native Plant Society and only in combination with several other factors. However, the identity of this “invasive species” is not clear. Rejmanek suggests that the “invasive species” rating refers to animal “invasions” by predators and grazers. He says, “Indeed, one needs quite a bit of imagination to predict that any native plant species may be driven to extinction by invasive plants per se.” (Marcel Rejmanek, “Vascular plant extinctions in California: A critical assessment,” Diversity and Distributions, Journal of Conservation Biogeography, 2017)
TC: 90% of all insect species are specialists that have evolved in concert with only one or a few plant lineages. How can they cope with the loss of native plants?
DT: Native plants are adapting in evolutionary time. Specialization is a continuum. Few insects are confined to a single plant species, some are confined to one or two genera, and others are confined to one or two families of plants. But if you are looking at the number of plants available to them, only about 7% of plants they are adapted to are available to them. 93% of available plants are not viable hosts for insects. Everything is a specialist on one level of another.
CSN: That sounds like an argument for a diverse garden, with many plant species that offer more food sources for insects. That doesn’t seem a sound argument for eradicating non-native plants.
TC: I understand that some native plants are more useful to insects than others?
DT: These are the keystone species. Many native plants don’t support insects because plants are well-defended against them. Keystone species are making most of the food for the food web. Just 14% of native plants across the country are making 90% of food that drive the food web. 86% of the native plants are not driving the food web. Insect food comes from the big producers, like oaks, black cherries, hickories, and birches.
CSN: That is a mind-boggling admission!! Earlier Tallamy complained that non-native plants are hosting only 34% of butterflies in California. Now he says that only 14% of native plants are useful to insects. He asks home gardeners to plant only native plants as well as limit our plantings to a small subset of native plants.
Tallamy’s ideology is antithetical to the goal of biodiversity, which could be the salvation of ecosystems in a changing climate. Since we can’t predict the climate of the future, biodiversity provides more evolutionary options, which increases the chances that some species will survive. Tallamy asks us to put a few eggs in the huge basket of our ecosystems, reducing their ability to survive the challenges of our changing climate.
For example, in Oakland, California, where I live, there were approximately 10 species of native trees prior to settlement. In 1993, there were 350 tree species in Oakland. (David Nowak, “Historical vegetation change in Oakland and its implications for urban forest management,” Journal of Arboriculture, September 1993) The recently published draft of Oakland’s Urban Forest Plan reports that there are now over 500 tree species in Oakland. I can’t fathom why Oakland would want to limit the planting of trees to only 10 native species.
I agree with Tallamy that many native plants are not useful to insects. I attend the annual conference of California Invasive Plant Council to give native plant advocates every opportunity to convince me of their viewpoint. At the most recent conference at the end of October, Corey Shake of Point Blue Conservation made a presentation about his project to “Evaluate native bee preference for common native and exotic plants.”
He designed 16 hedgerows around agricultural fields in Yolo County to determine if native bees have a preference for native plants or exotic plants, by controlling for availability of native plants compared to exotic plants. Here is his abstract:
“Farm edge restoration monitoring in Sacramento Valley highlights native bee use of some exotic plant floral resources. Corey Shake. Point Blue Conservation Science. cshake@pointblue.org
“Research of native bee preference for native versus exotic plant floral resources in California’s Sacramento Valley has shown mixed results. No studies have demonstrated a preference for exotic plants by native bees there, but some have highlighted the importance of exotic plant floral resources in plant-pollinator networks and expressed concern that rapid removal of exotic plants without restoring native plant populations could have negative impacts on native bees. We have been collecting native bee flower visitation, plant species, and floral abundance data on 16 farm edge restoration projects in Yolo County, California since 2019, which will allow us to assess bee preferences for some key native and exotic plants relative to their floral abundance. In our preliminary analysis, we see some important trends: (1) relative to their floral abundance in our plots, some native plant species are more frequently visited by native bees than other native plants that are infrequently or rarely visited, and (2) there is significant native bee visitation to some exotic plants relative to their floral abundance. We will further evaluate these data as well as our butterfly diversity and abundance data to provide plant-species specific insights to restoration practitioners and weed management specialists to help them reduce harmful impacts to native pollinators when executing restoration projects and managing weeds.”
In other words, not all species of native plants are useful to native bees and some species of non-native plant species are useful to native bees. Tallamy’s sweeping generalizations about the usefulness of native plants to insects are not supported by empirical or field studies. Although the characteristics of plants vary widely, the variation is unrelated to the national origins of plants.
From Micro to Macro Perspective
I recognize my voice in the questions Tom Christopher asked of Doug Tallamy, as well as Art Shapiro’s. Speaking for myself, not for Art, this interview misses the point of my criticism of native plant ideology. I like native plants as much as I like any plant and I encourage everyone to plant whatever they prefer. I only object to the pointless destruction of harmless non-native plants that thrive because they are best adapted to the conditions where they have naturalized. Non-native plants do particularly well in the wake of disturbance. Where they have replaced native plants, the natives were destroyed by disturbance, not by the hardy non-native plants that can tolerate disturbance. Non-native plants are a symptom of change, not the cause.
I object to destructive eradication projects because they poison the soil with herbicides, making it even less likely that non-native plants will be replaced by fragile native plants. I object to the loss of biodiversity which is a hedge against extinction in a rapidly changing climate. We don’t know which plants will be capable of surviving in the changed climate. We should not be taking cards out of the deck while we gamble with the future of the environment and everything that lives in it.
Unfortunately, native plant advocates take offense when anything positive is said about introduced plants. A positive statement about a non-native is routinely interpreted as a negative statement about native plants. It shouldn’t be. The emphasis on the negative assessment of introduced plants results in harmful land management decisions. The pros and cons of all plants should be considered before we condemn non-natives with a death sentence. Like our justice system for human society, all plants should be presumed innocent until proven guilty.
Thanks again for airing this debate on your podcast. I hope you will forward my email to Doug Tallamy
Juliet Stromberg is a plant ecologist who specialized in wetland and riparian ecosystems of the American Southwest. Her friends call her Julie and I will presume to do the same. She has retired from her position at Arizona State University, but her husband, Matt Chew, is still teaching ecology from a historical perspective at ASU. He is very much her partner in their 20-year project to restore 4-acres of dead citrus grove and an 80-year old Spanish colonial house, long abandoned and derelict. The property came with water rights, without which their project would not have been possible.
In her recently published book, Bringing Home the Wild: A Riparian Garden in a Southwest City, Julie tells us how she and her partner transformed—with the help of natural processes–this dead patch of land in South Phoenix, Arizona into the oasis that it is today. The first step was to restore the irrigation system, which immediately brought much of the dormant seed bank back to life.
Julie & Matt’s garden is in the center of this aerial view
Using the riparian vegetation of the Salt River—the source of their water—as her reference, she chose a half-dozen tree species as the foundation of their garden, such as Fremont cottonwood, Gooding’s willow, and velvet mesquite. Twenty years later, there are now 300 trees, sheltering a community of plants and animals. How did they get there?
The seeds of some trees such as blue elderberry and mulberry were brought from neighboring gardens by birds and small animals. Julie and Matt have seen 157 species of birds in their garden, so we can assume birds have done some of the planting. The seeds of some plants are aerodynamically shaped and were blown in by the wind, adding to the diversity of the garden.
Tropical milkweed seeds ready to be launched by the wind from a neighbor’s front yard. Conservation Sense and Nonsense, Oakland, CA, October 2023
Many of the trees are American in origin, but others are not. Regardless of the method of dispersal, most introductions are welcome in Julie’s garden. She spares her readers the tedious recitation of which plants are considered native and which are not. The Southwestern desert is not an ecosystem with which I am familiar. I was glad to have a tour of Julie’s garden without irrelevant information about the nationality of every plant. For the same reason, I like to travel in distant places where I can’t distinguish natives from non-natives. Everything looks great to me and nothing brings me down more than a guide who wants to inform us of what “belongs” and what doesn’t.
Julie and Matt also planted a fruit orchard and a vegetable garden that bring more birds, insects, and animals to the garden as well as providing food for their table. Eating the fruits of our labors in the garden deepens our respect for what plants do for us and establishes our working relationship with the land.
Managing a wild garden
In keeping with Julie’s opinion that ecological restoration is a form of “glorified gardening,” she actively manages her garden. A few plants that annoy members of her community of plants and animals—such as puncture vine and tumbleweed—are not welcome.
When the delicate balance between predator and prey becomes unbalanced, some protective measures are necessary. If coyotes and dogs can’t keep up with the rabbit population, it’s sometimes necessary to put vulnerable plants into cages to protect them. The root balls of some plants are covered in wire mesh to protect them from hungry gophers.
Plants also assist in their own defense. Where mesquite is grazed by cattle, the tree responds by growing longer thorns to repel the cattle. When plants are attacked by plant-eating insects, some emit a toxin to render themselves inedible. The scent of the chemical wafts to neighboring plants, alerting them to the arrival of predators. These natural defenses are an important line of scientific inquiry that has potential to substitute nature-based solutions for synthetic chemicals.
The population of roof rats in Julie’s home is kept in check with liquid birth control, lest they chew on electrical wires or build nests in car engines.
Gardening with the help of friends
Julie’s is not a manicured garden, but it requires constant pruning to keep trails clear and provide light and space for plants to thrive. The annual scouring of the flood plain by spring floods is one of the natural processes that Julie and Matt could not use to restore their land because irrigation water is channelized and confined by concrete. Julie has come to appreciate the flies and other insects who are the decomposing crew, helping to reduce the accumulation of debris in the absence of annual scouring floods. Sixty-six species of flies assist with decomposition as well as pollination in Julie’s garden.
Julie is happy to have coyotes in her garden, but her dogs disagree. Violent and fatal confrontations between these closely related species required building a wall that confines dogs close to the house at night, while coyotes safely roam most of the garden.
Dogs are an important part of Julie and Matt’s life. Early in the book’s introduction Julie warns readers that they should put her book down “NOW!” if they don’t want to hear dog stories. Julie has walked thousands of dogs in a nearby animal shelter. In addition to her own 4 dogs, there are also occasional foster dogs who need to recover from traumatic experiences to be adoptable. In Julie’s refuge, these traumatized dogs learn to trust again.
Peaceful co-existence
Julie is a recovering academic scientist. Before she retired, she felt that her focus on the accumulation of data needed for scientific analysis was causing her to lose track of the big picture. She needed to stop and smell the flowers, so to speak.
She received her graduate education during the heyday of invasion biology. Julie slowly shifted away from native purism based on her experiences in the field. She has rejected that doctrine, and regrets teaching her students to fear “those who came from somewhere else.”
Julie has a vivid memory of the first step she took on that journey to her gardening ethic of peaceful coexistence. She had been instructed to pull tree tobacco from land along the Salt River that was being restored. The nicotine in the plant was making her feel sick, which seemed to bring her to her senses. She began to wonder what she was doing, “following orders to kill creatures she barely knew.”
Fly on desert tobacco. Photo courtesy Juliet Stromberg
Part of Julie’s skepticism about such eradication projects is based on her understanding of how little we know. She realizes that the harm done by non-native species is exaggerated and their benefits are underestimated. Given the limits of our knowledge, we should be obligated to give introduced plants the benefit of the doubt before killing them. She now appreciates the beauty of tree tobacco, which also feeds birds, fixes carbon, and stabilizes the soil. Its seeds were naturally dispersed to Julie’s garden and tree tobacco is welcome there.
Imperatives imposed by climate change
Julie says, “The preoccupation with provenance diverts conservationists and gardeners from critical issues,” such as climate change, food security, and extinction (which, studies show, are not caused by introduced plants). Living in the Southwest, Julie has a front row seat on climate change. It’s always (within the context of our lifetime) been hot there, but now it is blisteringly hot during summer months. She watches hummingbirds in her garden seek shelter in the shade, close to the irrigation drip. She watches dogs panting, birds gasping for breath and plants wither and die in the heat. And she knows that both native and non-native plants store carbon that would otherwise contribute to greenhouse gases causing climate change. Carbon storage varies according to certain plant characteristics, but those characteristics are unrelated to the nationality of plants.
Those who insist on replicating the landscape that existed 200-400 years ago in America are depriving nature of the evolutionary opportunities that will enable survival. We don’t know what life will be capable of living in the climate of the near-future. Nature needs as many alternatives as possible to find the species that can survive. Plants and animals are blameless in this struggle of survival of the fittest. The least we can do is to get out of their way as natural selection finds the life that is adapted to the current and future climate.
Showing respect for nature
Julie does not use any pesticides in her garden….no herbicides, fungicide, or insecticide. She is concerned about the pesticides used by her neighbor across the road who grows cotton. She notices the blue cotton seeds scattered on the ground and surmises that they were coated in insecticide or herbicide that will infuse pesticide into the plant as it grows. The poisoned seed can kill seed-eating birds and other animals and the plant itself will be poisonous as it grows. The dust from the cotton field blows into her property when the field is plowed and after the cotton is harvested because no cover crops are grown to tamp down the dust and prevent the loss of carbon stored in the soil. Julie can see firsthand the damage caused by industrial agriculture and is confirmed in her commitment to avoid using pesticides.
Julie shows her respect for everything living in her garden by her choice of pronouns to describe them: “who” not “what,” “she/her” not “it.” She asks her readers to show the same respect for plants and animals, regardless of their nationality. Avoiding the use of pesticides in our gardens is another way to show our respect for the plants and animals on which we depend, with the added benefit of not poisoning ourselves.
Thank you, Juliet Stromberg, for telling us about your garden and congratulations for what you have accomplished and learned from the experience of nurturing it back to life with the help of nature.
Dana Milbank is a political commentator for the Washington Post. Like many city dwellers, Milbank moved his family from Washington DC to the Virginia countryside during the Covid pandemic.
His new home inspired him to become a native plant advocate with the usual corresponding hatred of non-native plants. He announced his new hobby of killing non-native plants in April 2023, as described in this response to his article by several defenders of the natural world as it exists, rather than as some might wish it to be.
In a more recent article, Milbank expressed his frustration at the failure of his early efforts to destroy non-native plants on his property without using herbicides: “When last I wrote about my battle of the brush, I was losing, badly, to the invasive vines and noxious weeds that had turned forest and field at my Virginia home into an impassable jungle. I’d cut them back, but they would return in even greater numbers.”
He justifies poisoning both his property and the Shenandoah National Park near his home by turning to advisors who tell him what he wants to hear, people who make their living using herbicides to eradicate non-native plants.
Of course, renowned native plant guru, Doug Tallamy, is one of his advisors. Although Tallamy advised residential gardeners against using herbicides in his book, Nature’s Best Hope, published in 2020, he has now changed his mind about herbicides. In Milbank’s article, Tallamy says that herbicides are an “essential tool:” “‘I think of it as chemotherapy,’ said Doug Tallamy, a University of Delaware entomologist and guru of the native-plant movement. ‘We have ecological tumors out there. If we don’t control them, we have ecological collapse. We have the collapse of the food web.’”
Poisoning the soil
Milbank admits that glyphosate (Roundup) is toxic and he wears protective gear when applying it, including a respirator (which is not required for glyphosate applications by California’s pesticides regulations). He describes his application technique: “My preferred technique is ‘hack and squirt.’ With my hatchet, I cut gouges around the circumference of the invading tree, then spray the poison inside. For smaller invaders, I can chop the whole thing down and apply the chemical as a ‘cut stump’ treatment.
I read most of the over one thousand comments on Milbank’s article to determine the public’s reaction. Although many commenters express reservations about the use of herbicides, the majority of commenters are supportive of the use of herbicides. The manufacturers of pesticides are definitely winning the public relations battle regarding chemical safety. When supporters reply to doubters of herbicide use, they defend Milbank’s application technique as “surgical.”
Cut stump and hack and squirt application methods are less likely to disperse chemicals in the air, but they increase soil contamination. These application methods work by applying herbicide shortly after the woody plant is cut, while the cambium layer (between the bark and the heart wood) is still functional. The cambium layer delivers the herbicide to the roots of the plant to kill the roots. The application may appear to be “surgical” from the standpoint of above-ground contamination, but the damage is being done in the soil, the plants growing in the soil, and the animals that eat those plants.
There are many consequences of poisoning the soil:
Because the roots of plants are intertwined as well as connected to one another by fungal networks in the soil, non-target plants are harmed and often killed. It is not possible to poison one plant without poisoning others. HERE is an example of a forest of native trees that was damaged by spraying herbicide under the trees.
Herbicides kill beneficial microbes and fungi in the soil that contribute to plant health. (1) For example, fungal networks that are killed by herbicides transport moisture and nutrients from the soil to the plants. Whatever vegetation remains or is planted in the future is handicapped by the loss of this living support system.
Glyphosate binds minerals in the soil, preventing essential nutritional minerals such as iron and manganese in the soil from being taken up by plants. (2) Glyphosate is so widely used that it is found in the blood and urine of most of the population, including children. Could glyphosate be a factor in widespread iron-deficiency anemia in adolescent girls and young women? (3)
Glyphosate is a well-known anti-microbial agent. These effects raise concerns regarding glyphosate’s influence on human health and behavior through secondary means, such as our gastrointestinal microbiome, given what is now known regarding the gut microbiome and its influence on human health and disease. (4,5)
Milbank repeats his accusation that those who believe the threat of non-native plants is exaggerated, are climate change deniers. He turns to the Executive Director of the federal Invasive Species Council for confirmation, who calls the threats of non-native plants “settled science.” Science is, by definition, never settled. Science is a process, not a conclusion. Every scientific hypothesis is constantly tested and usually refined or overturned as new knowledge and methods are available. Many scientists are testing the hypotheses of invasion biology and questioning their validity in a changing climate.
The only issue about invasion biology that is “settled” is that it has created a multi-billion dollar “restoration” industry that relies on and benefits the manufacturers of pesticides, as well as creating vested interests that perpetuate the industry.
Milbank also quotes one of his advisors who claims that native plants are better adapted to the changed climate than non-native plants: “The natives have the best ability to adapt — they’ve been adapting for tens of thousands of years in these areas — so they’ve got the ability to change as the climates and the landscapes have been changing.” This statement seems comical, given that the topic is the extreme difficulty of eradicating non-native plants and the fact that they are out-competing native plants. There is zero evidence that native plants are better adapted to the changed climate than the non-native plants that have replaced them. 500 million years of geologic history on Earth has informed us that when the climate changes—as it has many times–the vegetation changes.
All plants, whether native or non-native, convert carbon dioxide to oxygen and store carbon. Destroying them contributes to greenhouse gases causing climate change by releasing their stored carbon into the atmosphere and reducing the capacity of the landscape to absorb more carbon in the future.To deny that fact, is to be a climate change denier.
Reality trumps unrealistic hopes
Milbank describes the landscape he hopes to achieve with the help of herbicides. It is the landscape that existed in the distant past, in a different climate, before the environment was altered by the activities of humans. I am reminded of one of the presentations at the most recent conference of the California Native Plant Society, an event where the audience hopes and the speakers douse the audience’s hope with the reality of their unsuccessful efforts. The presenter described a 20-year effort at the Santa Rosa Plateau Ecological Reserve to convert non-native annual grassland to native grassland, using annual (sometimes bi-annual) prescribed burns. Many different methods were used, varying timing, intensity, etc. The abstract for this presentation reports failure of the 20-year effort: “Non-native grass cover significantly decreased after prescribed fire but recovered to pre-fire cover or higher one year after fire. Native grass cover decreased after prescribed fire then recovered to pre-burn levels within five years, but never increased over time. The response of native grass to fire (wild and prescribed) was different across time and within management units, but overall native grass declined.” The audience was audibly unhappy with this presentation. One person asked if the speaker was aware of other places where non-native grass was successfully converted to native grass. The speaker chuckled and emphatically said, “NO. I am not aware of any place where native grasses were successfully reintroduced.”
Dana Milbank is a political columnist for the Washington Post. He broke out of his political mold on April 7, 2023 to write an article about gardening published by the Post, which repeats every myth of the nativist ideology.
A team of dismayed critics of invasion biology has responded to excerpts of Milbank’s column:
Marlene A. Condon is a garden writer based in Virginia and the author of The Nature Friendly Garden. She has a degree in physics. Her entire critique of Milbank’s column is available on her website. Her comments address the reader.
Carol Reeseis a retired Extension Horticulture Specialist who conducted her 27 year career from the University of Tennessee’s West Tennessee AgResearch and Education Center in Jackson, where a large and diverse display garden gave her the opportunity to observe biodiversity in action on an enormous range of plant species from other parts of the world. She describes herself as a farm raised country girl tomboy who has looked at the natural world in hundreds of settings and landscapes, natural and manmade, and read countless books and articles. She has written for several magazines, newspapers, articles for Garden Rant as well as university publications. Her speaking engagements around the country have allowed her to engage with many other green industry professionals. Dana Milbank’s column prompted her to email him directly with her concerns, directly addressing some of his assertions. I publish some excerpts here from her emails sent directly to Milbank.
Conservation Sense and Nonsense is the webmaster of this website. I have studied invasion biology and the native plant movement it spawned for over 25 years. I’ve watched forests of healthy, non-native trees in California be destroyed and replaced by weedy grassland. I have used what I have learned to advocate for a less destructive approach to restoration, a word I am reluctant to use to describe projects that use herbicides to eradicate harmless plants and trees. My comments are addressed to the reader.
What follows are excerpts from Dana Milbank’s column with responses from Marlene Condon, Carol Reese, and Conservation Sense and Nonsense, just three of many skeptics of invasion biology. To summarize the point of our criticism:
Insects are not dependent on native plants. They are just as likely to use related non-native plants in the same genus or even plant family with similar chemical properties and nutritional value.
While some non-native plants have potential to be harmful, many are beneficial. There are pros and cons to both native and non-native plants and that judgment varies from one animal species to another, including humans. For example, we don’t like mosquitoes, but they are important food for bats and birds.
All plants, whether native or non-native convert carbon dioxide to oxygen and store carbon. Destroying them contributes to greenhouse gases causing climate change.
When the climate changes, vegetation must also change. Many non-native plants are better adapted to current climate and environmental conditions in disturbed ecosystems.
Conservation Sense and Nonsense
“I’m no genius about genuses, but your garden is killing the Earth” By Dana Milbank Washington Post, April 7, 2023
Milbank: I did almost everything wrong.
Reese: I’m so sorry you thought this!
Milbank: For 20 years, I found the latest, greatest horticultural marvels at garden centers and planted them in my yard: sunny knock-out roses, encore azaleas, merlot redbud, summer snowflake viburnum, genie magnolia, firepower nandina
In between them flowed my lush, deep-green lawn. I hauled sod directly from the farm and rolled it out in neat rows. I core-aerated, I conditioned, I thatched, I overseeded, I fertilized. I weeded by hand, protecting each prized blade of tall fescue from crabgrass and clover.
In this season, a symphony of color performs in my yard. The fading daffodils, cherry blossoms, saucer magnolias, hyacinths and camellias meet the arriving tulips, lilacs, creeping phlox and azaleas, with the promise of rhododendrons, peonies, hydrangeas, day lilies and roses to debut in the coming weeks.
But this year, the bloom is off the rose. And the hydrangea. And the rhododendron. And all the rest. It turns out I’ve been filling my yard with a mix of ecological junk food and horticultural terrorists.
Condon:When Mr. Milbank posits that he’s “been filling his yard with a mix of ecological junk food and horticultural terrorists,” he’s channeling the kind of words Bringing Nature Home author Doug Tallamy loves to employ: Biased expressions that implant negative images in the reader’s mind so he will become yet another minion of this scientist. Nowadays you can’t read a garden or environmental column without being accosted with the same words or variations thereof, as if everyone has become a mouthpiece for Doug Tallamy, which I’ve never seen done more obviously than in this column by Dana Milbank.
Conservation Sense and Nonsense: Milbank’s lengthy list of “bad” plants in his garden paints with too broad a brush. For example, instead of identifying a particular species of hydrangea and rhododendron, Milbank condemns an entire genus. Both hydrangea and rhododendron genera have several native species within the genus. Most (all?) species of phlox are also native to North America.
Milbank: When it comes to the world’s biodiversity crisis — as many as 1 million plant and animal species face near-term extinction because of habitat loss ― I am part of the problem. I’m sorry to say that if you have a typical urban or suburban landscape, your lawn and garden are also dooming the Earth.
Reese:YIKES! This is pretty extreme, and dare I say inaccurate? No, home gardeners are part of the solution, no matter the plants in their garden. Doom will come from lack of diverse green space. Doom will come from climate warming as a result, as well as from pollution, tillage, factory farming and development.
Milbank: I came to understand the magnitude of my offenses after enlisting in nature boot camp this spring. I’m in “basic training” with the state-sponsored Virginia Master Naturalist program. While others sleep in on rainy weekend mornings, my unit, the Arlington Regional Master Naturalists, has us plebes out in the wetlands distinguishing a yellow-bellied sap sucker from a pileated woodpecker.
I’m no genius with genuses, but I know a quercus from a kalmia, and because of my gardening experience, I began the program with confidence. Instead, I’ve discovered that all the backbreaking work I’ve done in my yard over the years has produced virtually nothing of ecological value — and some things that do actual harm.
A few of the shrubs I planted were invasive and known to escape into the wild. They crowd out native plants and threaten the entire ecosystem. Our local insects, which evolved to eat native plants, starve because they can’t eat the invasive plants or don’t recognize the invaders as food.
Anise swallowtail on non-native fennel. Courtesy urbanwildness.org “Papilio zelicaon, the anise swallowtail, typically has one to two generations in the mountains and foothills of California where it feeds on native apiaceous hosts. However, along the coast, in the San Francisco Bay Area and the urbanized south coastal plains and in the Central Valley, P. zelicaon feeds on introduced sweet fennel, Foeniculum vulgare, and produces four to six or more generations each year… the use of exotics has greatly extended the range of P. zelicaon in lowland California.” SD Graves and A Shapiro, “Exotics as host plants of the California butterfly fauna,” Biological Conservation, 2003.
Reese:It sounds so logical, but is sooo inaccurate. Ask any entomologist that has spent their careers “fighting pests” on valued crop or ornamental plants. Remember Pangea [when all continents were fused into one]? More recently, have you thought about the exchange of plants and animals across Berengia when we were still connected to Asia? We can trace those relationships/kinships of our plants to Asian/Eurasian plants now through DNA. They eventually differentiated into species (a continuum of change caused by climate and geologic pressures until we [Man] declare it as a different species, though biologically it is still basically the same nutritional makeup)
Condon also dissects Milbank’s statement:
“They crowd out native plants and threaten the entire ecosystem.” Read virtually any description of where you find so-called invasive plant species and you will find the word “disturbed.” This tells you the soil profile has been negatively impacted by people, animals, or weather, and usually means the topsoil is gone. Only very tough plants—known as colonizers—can grow in disturbed areas because the soil is nutrient-poor and is typically compacted. Consequently, these areas may fill with a mix of native and nonnative plants, or mainly one or the other—but every single plant is a colonizer that is working to rehabilitate the land for the benefit of the native plants that require topsoil in which to grow. “Invasiveness” is nothing more than a derogatory word used by people with contempt for alien-plant colonization. Conclusions: Alien plants can’t “crowd out” native plants because once the soil is disturbed and thus degraded, most of our native plants can’t grow there and thus are not there to be crowded out. As for “threatening the entire ecosystem,” to the contrary, alien colonizers are helping to restore it.
“Our local insects, which evolved to eat native plants, starve because they can’t eat the invasive plants or don’t recognize the invaders as food.” This oft-repeated distorted premise comes straight out of Bringing Nature Home, in which Doug Tallamy deceptively writes about “an excellent demonstration of how restricted a specialist’s [an insect with particular food preference] diet is.” Tallamy tells the story of Eastern Tent caterpillars on a cherry tree denuded of its own leaves but hosting a Japanese Honeysuckle vine. He writes that the caterpillars didn’t recognize the honeysuckle as food (sound familiar?) But, of course, they didn’t because this species of insect can only eat plants in the Rose Family, which does not include honeysuckle. What Doug Tallamy doesn’t tell the reader is that the tent caterpillars could certainly have eaten the so-called invasive Multiflora Rose, which I’ve documented in the photo below. Conclusion: Native insects did not evolve to eat only local (native) plants, but rather can typically feed upon dozens, if nothundreds or thousands, of plants related to each other by family classification, even though they grow in other countries.
Tent caterpillar on multiflora rose. Photo by Marlene Condon.
Milbank: This in turn threatens our birds, amphibians, reptiles, rodents and others all the way up the food chain. Incredibly, nurseries still sell these nasties — without so much as a warning label.
Reese:As I read, I also watch the many birds on my lawn, the fence lizards on my decks, the insects humming among the flowers in my diverse collection of native cultivars and introduced plants.
Hummingbird in eucalyptus flower. Eucalyptus blooms from November to May. It is one of the few sources of nectar and pollen for birds and bees during the winter months when little else is blooming. Courtesy Melanie Hoffman
Eucalyptus leaf litter makes excellent camouflage for this garter snake. Courtesy Urban Wildness
Milbank: Most of my other plants, including my beloved lawn, are ecological junk food.
Reese:Now, now! Many (most) natives do not supply useful forage either. All plants supply some benefit. They provide shelter, create, improve and anchor soil, cleanse air and water, make oxygen and cool the planet. The plant must be judged on benefits versus detriments in each situation. If a nonnative plant is the only thing that will flourish in bombed out rubble, or contaminated soil, if it is providing many benefits, shall we rip it out because caterpillars won’t eat it? If we let it get established, will it ready the site for other species with more benefits to become established? Shall we get out of the way and let nature do what she does, which is heal herself?
Milbank: The trees, shrubs and perennials are mostly “naturalized” plants from Asia or Europe or “cultivars,” human-made varieties of native plants bred to be extra showy or disease resistant but lacking genetic diversity or value to animals. I, like other gardeners I know, planted them after mistaking them for their native cousins. They’re not doing harm, but neither are they doing anything to arrest the spiral toward mass extinction.
Reese:Please know that the most influential native plant botanical garden in the country (Mt. Cuba Center) has trialed the cultivars of native plants for their ecological benefits and found as should be expected, that each cultivar must be judged on its own merits. Some are better than the straight native as in the coneflowers where ‘Fragrant Angel’ scored tops for pollinators and many others were very close to being as good as straight species. These cultivars were even better than the other species of Echinacea tested. BTW, I grow E. purpurea, pallida, paradoxa, tennesseensis and laevigata as well as many cultivars. Remember that cultivars should also be judged on not just nutritional value, but other factors that increase benefits, such as length of bloom period, numbers of blooms, drought resistance, heat tolerance, hardiness, ease of production (cost) and durability. Please ask to speak to Sam Hoadley there as he leads the research on beneficial cultivars and has completed and undertaken several studies of different native species. Great guy and great speaker.
Please be aware that many cultivars originated as naturally occurring deviations in seedling populations, and as we know this actually diversifies the genetic pool, allowing Mother Nature to select the better form. We sometimes agree with her, and other times we may move along that diversifying form by crossing it with others that are demonstrating genetic variance. Logically, this actually furthers the cause of a broader genetic pool that can help in today’s crisis in showing which can cope and flourish.
Milbank: To get a sense of my missteps, I asked Matt Bright, who runs the nonprofit Earth Sangha, a native-plant nursery in Fairfax County (and a lecturer on botany for my nature boot camp) to walk through my yard with me.
He took aim at my day lilies: “I would remove them all. Those have also become badly invasive.”
He spied my creeping jenny on a slope: “Another nasty invasive.”
He condemned to death my rose of Sharon shrubs (natural areas “have really been torn up by these guys”) and my innocuously named summer snowflake viburnum.
Worst was my row of nandinas — “heavenly bamboo” — along the foundation. “You definitely want to remove it,” he advised. Its cyanide-laced berries poison birds.
Condon:This tactic is typical of the followers of Tallamy who want folks to perceive supposedly invasive plants as “bad” even though no evidence exists to support their accusations, especially in this instance. Mr. Milbank and Mr. Bright, who obviously supplied this information, have misspoken here. A study out of the University of North Carolina, Chapel Hill, published in 2022, explains that Cedar Waxwings are the only birds that might be poisoned, and that’s only going to happen if someone grows so many nandinas that these birds consume large numbers of fruits in a single feeding bout. If you grow just one or even a few plants, you are not going to poison waxwings.
Conservation Sense and Nonsense: Here in California, most berry-producing, non-native plants are considered “invasive” based on the assumption that birds eat the berries and spread the plants. Nandina was briefly on the list of invasive plants in California until knowledgeable people informed the California Invasive Plant Council that birds don’t eat the toxic berries. Nandina was removed from the invasive plant inventory long ago.
Bumblebee on Cotoneaster, Albany, CA. Cotoneaster is one of many berry-producing non-native plants on the list of invasive plants in California. Himalayan blackberries are another target for eradication in California. They are frequently sprayed with herbicide in public parks where children and other park visitors eat the blackberries.
I also have personal experience with nandina and cedar waxwings. Flocks of waxwings visited my holly trees in San Francisco every year. They did not touch my three nandina plants.
California buckeye (Aesculus californica) is an example of a native tree that is toxic. Its flowers are toxic to honeybees and its big brown seeds for which it is named were used by Indigenous people to stun fish to make them easier to catch. The bark, leaves, and fruits contain neurotoxic glycoside aesculin. Every negative characteristic attributed to some non-native plant species is equally true of some native plant species. No one mentions buckeye’s toxic characteristics because it’s a beautiful native tree. Photo Sacramento Tree Foundation
Condon: I’ve had a Rose of Sharon (Hibiscus syriacus) growing in my yard since I moved to my home in Virginia almost 40 years ago. In all this time, only one seedling from the plant I brought here has ever “volunteered” to become a second yard denizen. During the past 37 years, pollinators have fed at the original plant and then also at its offspring. What I’ve found by experience in my yard is that few plants can successfully move into a space that’s already filled with other plants. (Proving what physics tells us–that no two physical objects can occupy the same space). I’ve brought home numerous so-called invasive plants, only to have them disappear or simply stay put where I planted them. That’s because hundreds, if not thousands, of plants fill my yard.
Conservation Sense and Nonsense: Virginia is one of only four states in which rose of Sharon is considered invasive. Condon’s experience with rose of Sharon in Virginia suggests that lists of “invasive plants” are either inaccurate or are serving another purpose (perhaps both). The longer the list of “invasive plants” the more work is created for the “restoration” (AKA eradication) industry.
Rose of Sharon is not considered invasive in California. This is a reminder that the behavior of plants varies because of the wide range of climate and environmental conditions. Nearly one third of the plants on California’s list of invasive plants are not considered invasive in California. They are on the list because they are considered invasive in Hawaii, a state with a warmer, wetter climate than California. In naming rose of Sharon as a dangerous invasive, a media resource with a national readership has made a generalization that red-lines more plants than necessary. They become targets for eradication with herbicide and they deprive us of the biodiversity that is particularly important in a changing climate in which biodiversity ensures resiliency.
Milbank: Bright did praise two “good” species I have that contribute to biodiversity: a sycamore and a catalpa as well as a “great” American elm and a “phenomenal” dogwood. (I couldn’t take much pride in them, though, because all four were here long before I arrived.) And Bright assured me I wasn’t a particularly egregious offender; my one-sixth acre lot in town is typical of the urban/suburban landscape.
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Lawns, and those useless, ubiquitous cultivars of trees, shrubs and perennials sold by the major garden centers, aresquelching the genetic variety nature needs to adapt to climate change.
Reese:It’s actually the opposite. We need more plants in the mix. We need “the tumult of nature” to decide. We aren’t the jury, and we continue to interfere with our well-intended assumptions that we know best.
Lawns are full of wildlife when management is minimal. Mow. That’s all. Mow judiciously when “lawn weeds” are blooming. Watch birds feed on the many insects in the lawn including lepidopteran larvae. Realize that many moths pupate underground. Think of your lawn as haven for them and for the grubs birds relish as millions of acres across our country are being tilled for factory farms. Remember that the best habitat is mixed. Open areas bordered by wooded areas and most species love the borders. Our suburban landscapes are ideal if we just stop killing things.
Milbank: The resulting loss of native plants in our fragmented urban and suburban landscapes deprives both plants and wildlife of the contiguous habitats they need to breed and, over time, to migrate in response to climate change.
The deck is stacked against nature in this fight.
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If possible, you should remove the nastiest of the invasive plants if you have them: burning bush, Japanese barberry, Asian bush honeysuckle, English ivy, callery (Bradford) pear and a few others.
But leave the rest of your plants alone, for now. Tallamy ultimately wants to cut lawn acreage in half, but “there is room for compromise,” he said. Think of your noninvasive plants and cultivars as “decorations.”
Janet Davis, who runs Hill House Farm & Nursery in Castleton, Va., has a similar message for the purists who make you feel bad about your blue hydrangea. “Don’t give me crap about something that’s not native but not invasive,” she said. “I’m never going to tell you you can’t have your grandmother’s peony.”
Thus absolved, I shed my guilt about my yard full of ecological empty calories. I kept my hydrangeas, azaleas and roses but pulled out the truly bad stuff. I dug up the nandinas and replaced them with native winterberry holly, red chokeberry and maple-leaf viburnum. I removed the rose of Sharon and substituted American hazelnut and witch hazel. I uprooted the invasive viburnum and planted a native arrowwood viburnum in its place.
I also took a small step in the painful task of killing my beloved lawn. I used landscape fabric to smother about 400 square feet of turf. In its place, I planted a smattering of canopy trees (two white and two northern red oaks), understory trees (ironwood, eastern redbud), shrubs (wild hydrangea, black haw viburnum) and various perennials and grasses (Virginia wild rye, blue-stemmed goldenrod, American alumroot, woodrush, spreading sedge).
My 38 plants cost $439 at Earth Sangha. But these natives, adapted to our soil and conditions, don’t require fertilizer, soil amendments or, eventually, much watering. Over time, I’ll save money on mulch and mowing.
Reese:This one is so oft repeated and so very wrong. It depends on the plant, and it depends on the site. Plants in the wild require no input to succeed whether native or not because we have not messed up the soil and we have let the natural cycles of plant debris/decay improve the soil as it was meant to, creating a live, moist, interaction of microorganisms that work symbiotically to support the plant, which, btw has also been selected by nature for that site. It has absolutely nothing to do with origins. In fact, why would nonnative plants become “invasive” if they did not adapt as well or better than the native plants? I want to snort with laughter!
Milbank: Right now, my seedlings look pretty sad. Where once there were healthy lawn and vibrant shrubs, there is now mud and scrawny sprigs poking from the ground every few feet. I put up chicken wire to keep the kids (and me) from trampling them. The carcasses of my invasive plants lie in a heap on the gravel.
Condon: This statement supports my contention that ridding your yard (and, in the case of government, natural areas and parks) of “invasive” plants destroys habitat, leaving our wildlife high and dry. Follow the advice of Doug Tallamy, via Dana Milbank (and many others) and you make the environment far less hospitable to our wildlife by removing plants that supplied habitat NOW when our critters need it to survive.
Conservation Sense and Nonsense: This description of Milbank’s ravaged garden is consistent with my 25 years of observing native plant “restorations” on public land. They all begin with destruction, usually accomplished with herbicides. The first stage of these projects is often described as “scorched earth.” Years later, there is rarely habitat comparable to what was destroyed. Colored flags usually outnumber plants.
This is what a native plant garden on Sunset Blvd in San Francisco looked like after two years of effort: more colored flags than plants. The sign claims it is “pollinator habitat.” Since when do pollinators eat flags?
Milbank: But in a couple of seasons, if all goes well, my yard will be full of pollinators, birds and other visitors in need of an urban oasis. Years from now, those tender oak seedlings, now 6-inch twigs, will stretch as high as 100 feet, feeding and sheltering generations of wild animals struggling to survive climate change and habitat loss.
Conservation Sense and Nonsense: Destroying harmless vegetation contributes to climate change by releasing carbon stored in the living vegetation and reducing the capacity to sequester more carbon. Above-ground carbon storage is proportional to the biomass of the living vegetation. Destroying large, mature plants and trees releases more greenhouse gases in the atmosphere than the young plants and trees can sequester. Meanwhile, the climate continues to change and the native plants that Milbank prefers are less and less likely to be adapted to conditions. Native plant ideology is a form of climate-change denial.
A small forest of non-native trees was destroyed in a San Francisco park to create a native plant garden. Nine months later, this is what the project looked like: a tree graveyard.
Milbank: I won’t be alive to see it. Yet even now, my infant oaks give me something the most stunning cherry blossom never could: a sense of hope.
Conservation Sense and Nonsense: I feel bad for Dana Milbank. He has been successfully guilt-tripped into believing he has damaged the environment. He hasn’t, but destroying his harmless garden WILL damage the environment.
We hope he will find his way back to a less gloomy outlook on nature, which will outlast us all in the end. Altered perhaps, but always knowing best what it takes to survive. The way back from the cliff he is standing on is through a study of evolutionary change through deep time to appreciate the dynamic resilience of nature, which may or may not include humans in the distant future. Our message is “Embrace the change because change will enable survival.”
Suggested reading for those standing on the steep cliff created by nativism in the natural world:
California’s Department of Pesticide Regulation (DPR) has published a draft of a policy that would replace its Integrated Pest Management policy with a Sustainable Pest Management (SPM) policy that is different in name only. SPM makes a commitment to continue using pesticides in California until 2050, and by implication, beyond. It makes NO commitment to reduce pesticide use or reconsider the current targets of pesticide applications. It claims that the health hazards and damage to the environment will be reduced by identifying “Priority Pesticides” for possible substitution or “eventual elimination.” It doesn’t commit to identifying any specific number of dangerous pesticides nor does it provide specific criteria for selecting these dangerous products. It claims that increased testing and development of new products will result in safer products and puts these judgments into the hands of “stakeholders” with “experiential and observational knowledge” rather than scientists with expertise in soil science, endocrinology, toxicology, epidemiology, biology, botany, horticulture, etc. The “stakeholder” committee that wrote the SPM proposal for urban areas included the manufacturer of pesticides and other users and promoters of pesticides.
That’s not an exhaustive list of the many faults of SPM and the dangers that lurk in it. I hope you will read it yourself and consider writing your own public comment by thedeadline on Monday, March 13, 2023, at 5 pm. The document is available HERE. It’s less than 100 pages long and it is a quick read because it is basically a collection of bullet-points.
This is how to comment: “DPR is accepting public comments to inform the prioritization and implementation of the Roadmap’s recommendations through March 13, 2023 at 5 p.m. Comments can be shared in writing to alternatives@cdpr.ca.gov or by mail to the department at 1001 I Street, P.O. Box 4015, Sacramento, CA 95812-4015.” Please note that Department of Pesticide Regulations is not offering revisions, only “prioritization and implementation.”
My public comment on California’s “Sustainable Pest Management Roadmap”
A summary of my public comment is below. A link to the entire comment is provided at the end of the summary:
Public Comment on “Sustainable Pest Management Roadmap” (AKA “Pathway to poisoning the environment for another 25 years”)
My public comment is focused on pesticide use in urban areas because of my personal experience and knowledge of pesticide use where I live. These are the broad topics I will cover in detail with specific examples later in my comment:
Since glyphosate was classified as a probable carcinogen by the World Health Organization in 2015 and the manufacturer of glyphosate settled 100,000 product liability lawsuits by awarding $11 billion to those who were harmed by glyphosate, public land managers have been engaged in the process of substituting other, usually equally or more dangerous herbicides for glyphosate to deflect the public’s concerns. The Sustainable Pest Management Roadmap (SPM) formalizes this process of substitution without addressing the fundamental problems caused by pesticides.
SPM endorses the status quo that exists now. Affixing the word “Accelerating” to SPM is an extreme case of double-speak that deliberately obscures, disguises, distorts, or reverses the meaning of words. SPM ensures that toxic pesticides will be used in California for more than 25 years, to 2050, and likely beyond. SPM therefore accelerates the damage to the environment that is occurring now. Given that climate change will enable the movement of more pests into areas where they are now suppressed by weather, greater use of pesticides should be anticipated so long as the underlying issue is not addressed.
The underlying issue is that pests have been identified for eradication that in some cases cannot be eradicated and in other cases should not have been identified as pests either because they are innocuous or because of the valuable ecological functions they perform. The key question that SPM does not address is whether pesticide use is truly necessary in the first place. Unless we focus on whether a pesticide is actually necessary, all other issues are merely window dressing for perpetual pesticide use.
SPM proposes to identify “Priority Pesticides” for possible substitution without any clear definition of “Priority Pesticides,” a process that is ripe for manipulation. Given the substitutions that are occurring now, we cannot assume that further substitutions would be less toxic. SPM puts the classification of “Priority Pesticides” into the hands of “stakeholders” without clearly identifying who stakeholders are. SPM says “stakeholders” were involved in the development of the proposed policy. Those stakeholders included only users and promoters of pesticide use. There was no representation on the Urban Sub-Group of organizations such as Californians for Pesticide Reform, California Environmental Health Initiative, Beyond Pesticides, Center for Environmental Health, Environmental Working Group, etc. Nor was there any visible expertise in the fields of science that are capable of analyzing and evaluating the impact of pesticides, such as soil science, endocrinology, toxicology, entomology, botany, biology, or horticulture. SPM ensures that this exclusion will continue during the implementation phase by suggesting that “experiential and observational” knowledge should be represented on an equal footing with undefined “science.” The word “science” is being used and abused by advocates for pesticide use who dangle it as a magic talisman, conferring fraudulent credibility.
Conservation Sense and Nonsense 