invasion biology – Conservation Sense and Nonsense

Life on Earth has saved itself many times without help from humans. It must do so again.

“What exists now can only ever come from what came before.” –Thomas Halliday, Otherlands

The consequences of climate change were more severe this summer than ever before:

Many places around the globe experienced extreme and prolonged heat waves.
Extreme heat caused wildfires in many places around the world.
There were also many severe floods all over the world.
The collapse of a glacier and the bedrock under it killed thousands of people in Nepal and warned of similar cataclysmic events elsewhere in the future.
NOAA is predicting the strongest El Niño on record in 2026-2027. It is expected to cause heavy rain in some places (such as California) and extreme droughts in other places around the world.

America is unwilling to do anything to reduce greenhouse gases causing climate change. In fact, we are developing more sources of fossil fuels and preventing the development of renewable sources of energy that do not contribute to greenhouse gases causing climate change.

Today, I would like to put these radical changes in our planet into some perspective, by revisiting some of the many catastrophic changes on Earth in the 4.6 billion years of its existence. In the 3.7 billion years that life has existed on Earth, 98% of all living species have become extinct. The species that survived those events were best adapted to the changed environment and many more evolved as conditions allowed. There are more species of plants and animals now than ever before, but many are threatened by climate change.

Homo sapiens have lived on Earth for only about 300,000 years. Clearly, humans have had little to do with the appearance of new species or the disappearance of extinct species over 3.7 million years until humans initiated the current round of climate change by burning fossil fuels to power our economy.

We must look to nature to save itself. Humans are not capable of doing so. In fact, we are standing in the way. Today, I am republishing an article that explains how nature has survived for billions of years without the “help” of humans and will do so again if we let it.

Conservation Sense and Nonsense

Let Evolution Lead the Way to Adaptation and Survival of Life

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.

This graph of global mean surface temperature on Earth in the past 485 million years tells us the Earth’s climate has been mild since humans evolved. The graph should help us understand the potential for the Earth’s climate to increase beyond the tolerance for human life.

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 18^th 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.

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 600 genetic tests are required every year 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
https://www.nytimes.com/2024/01/04/science/flower-sex-evolution-bees.html?searchResultPosition=1
https://en.wikipedia.org/wiki/List_of_C4_plants
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

Originally published March 1, 2024

“Ecosystems persist because they are capable of transformation, not because they resist.”

Please join me in welcoming Megan Bonnett to the team of contrarians who don’t believe that native plants are the salvation of nature. Nature will be its own savior, if we let it. With Megan’s permission, we publish one of the articles on her Substack, “Here and There.” Megan takes us, step-by-step through the processes of evolution that enable life on Earth to survive the radical changes that Earth has endured for 3.5 billion years without the “assistance” or interference of humans.

Megan Bonnett is a naturalist, independent ecology researcher, and science communicator whose work explores ecological theory, the history of invasion biology, and the philosophical assumptions that shape modern conservation.

She grew up in central Texas in a family of nature lovers, where countless hours spent outdoors cultivated both a deep affection for the living world and an insatiable curiosity about how it works. She later studied wildlife biology at Texas State University and spent more than a decade working as a naturalist and outdoor educator for organizations throughout the Austin area.

Long before ecology became the focus of her research, Megan developed what she can only describe as a calling to investigate incongruities–to follow the places where accepted narratives and observable reality don’t quite align. Through many challenging experiences in her young life and a propensity for deep observation of the goings-on around her, she became acutely aware of the gap that can exist between what people profess and what they practice. Rather than extinguishing that instinct by outsourcing her intellectual autonomy to the people who professed and practiced different things, she embarked on a path in the sciences and simply redirected it. The same habit of carefully examining assumptions, asking uncomfortable questions, and comparing ideas with evidence became the foundation of her work as a naturalist and researcher.

After another decade as an independent outdoor educator and guide, that curiosity led her to ask why so many aspects of invasion biology seemed internally inconsistent. What began as a handful of questions grew into a years-long investigation of ecological research, the history of the discipline, and the philosophical frameworks that have shaped modern conservation. When the COVID lock downs began and she could no longer teach in the field, she began to communicate her findings by various other means, turning her in-person outdoor education into online science communication.

Today, her work seeks not only to better understand ecological systems, but also to examine the assumptions that guide how humans interpret and manage them. She believes that every scientific discipline benefits from thoughtful self-examination, and that questioning long-held ideas is an essential part of scientific progress. Her writing explores where evidence, philosophy, history, and ecology intersect, inviting readers to look beyond familiar narratives and reconsider the questions themselves.

Conservation Sense and Nonsense

Post-Anthropocentric Ecology

Abstract

Conservation biology has long framed non-native species as symptoms of ecological degradation, positioning extinction, migration, and novel species assemblages as failures requiring correction. This paper advances a post-anthropocentric ecological framework that challenges these assumptions by re-centering ecosystems as self-organizing, adaptive systems operating across deep evolutionary time. Drawing on disturbance ecology, niche construction theory, and emerging work on novel ecosystems, it argues that migration and species replacement are not pathologies but core mechanisms through which ecosystems heal, reorganize, and persist under changing constraints. Extinction, while affectively charged for humans, is reframed as a natural–often necessary–component of systemic adaptation rather than an intrinsic ecological wrong. By interrogating the moral, temporal, and ontological assumptions embedded in invasive species discourse, this critique proposes a shift from origin-based conservation toward functional, process-oriented stewardship grounded in humility, restraint, and trust in the adaptive intelligence of living systems.

Introduction: The Limits of Anthropocentric Conservation

Modern conservation biology presents itself as a science of protection, yet its foundational assumptions remain deeply anthropocentric. Despite rejecting overt human dominance over nature, conservation practice continues to privilege human temporal scales, moral intuitions, and historical preferences when defining ecological harm. Ecosystems are treated as if they possess an optimal past state to which they ought to be returned, and deviation from this state–particularly through the arrival of non-native species–is framed as ecological error.

Nowhere is this framing more pronounced than in “invasive” species discourse. Migrant species are routinely characterized as threats, symptoms of degradation, or agents of collapse, with management efforts focused on eradication and control. Yet this perspective sits uneasily with what ecology itself reveals: that ecosystems are non-equilibrial, historically contingent, and fundamentally shaped by disturbance, dispersal, and replacement (Pickett & White 1985; Wu & Loucks 1995).

This paper argues that the invasive species paradigm reflects not ecological necessity but a residual anthropocentrism- an insistence that ecosystems conform to human concepts of order, identity, and permanence. A post-anthropocentric ecology, by contrast, would evaluate ecological change in terms of process, function, and adaptive emergence across deep time, rather than fidelity to culturally salient baselines.

Ecosystems as Self-Organizing Processes

Ecological systems are not archives of species composition but dynamic processes involving flows of energy, nutrients, organisms, and information. The persistence of ecosystems arises not from stasis but from continuous reorganization under changing conditions. Disturbance is not an interruption of ecological order but one of its primary drivers (Holling 1973).

The historical baseline model of conservation presumes that a particular moment in ecological history–often coinciding with early modern human observation–represents a normative state. Yet paleobiology and disturbance ecology reveal no such equilibrium. Species assemblages have always been provisional, repeatedly dismantled and reassembled through climatic shifts, geological events, and biotic interactions (Benton 2009).

From this perspective, ecological change is not a deviation to be corrected but an expression of systemic responsiveness. Ecosystems persist because they are capable of transformation, not because they resist it.

Migration as an Adaptive Response, Not a Pathology

Species dispersal has been the primary mechanism by which life responds to environmental change throughout Earth’s history. Ice ages, continental drift, mass extinctions, and atmospheric transformations all produced waves of migration and novel assemblages, none of which were constrained by notions of nativeness or historical fidelity.

Contemporary migration is often treated as uniquely pathological because it occurs within human-altered landscapes. Yet this framing introduces a qualitative distinction unsupported by ecological theory. While human activity accelerates change, ecosystems respond to altered constraints in the same way they always have–through redistribution, replacement, and innovation.

The emerging literature on novel ecosystems acknowledges this reality, recognizing that many contemporary ecosystems have crossed thresholds beyond which historical restoration is neither possible nor ecologically meaningful (Hobbs et al. 2006; Hobbs et al. 2013). In such contexts, migrant species often function not as disruptors but as pioneers and engineers facilitating system-level reorganization.

Case Studies in Functional Emergence

Nitrogen-Fixing Trees in Degraded Tropical Landscapes

In post-agricultural and post-mining tropical soils, native forest species frequently fail to re-establish due to severe nutrient depletion. Non-native nitrogen-fixing trees such as Leucaena, Acacia, and Albizia often colonize these landscapes rapidly, restoring nitrogen availability, increasing soil carbon, and facilitating successional processes that would otherwise stall.

Studies in Puerto Rico demonstrate that such species do not necessarily suppress biodiversity long-term, but instead enable the emergence of stable, productive forest systems that differ compositionally from historical baselines yet function ecologically (Lugo 2004). Here, migrant species act as metabolic catalysts, repairing biogeochemical cycles rather than displacing intact systems.

Ariel Lugo overlooking an urban watershed in Puerto Rico. Photo courtesy of Ariel Lugo.

Tamarisk and Riparian Reorganization in the American Southwest

Tamarisk (Tamarix spp.) has long been framed as an invasive villain in the Southwestern United States. However, research reveals that its dominance coincides with dam-altered hydrology that prevents the regeneration of native cottonwoods and willows. In the absence of natural flood pulses, the historical riparian system is no longer viable.

Tamarisk defoliated by intentionally introduced tamarisk leaf beetle along Colorado River, near Needles, California. Source: https://www.al-ipc.org/wp-content/uploads/2017/12/Norelli.pdf

Climate-Driven Mangrove Expansion

Poleward mangrove expansion into salt marsh ecosystems is frequently described as biological invasion. Yet this process reflects climate-driven adaptation rather than ecological breakdown. Mangroves increase coastal carbon sequestration, enhance shoreline stability, and replace marsh functions under warming conditions (Saintilan et al. 2014).

In this context, nativeness dissolves as a meaningful category. What persists is function- coastal protection, productivity, and resilience- carried forward by different species under new constraints.

Mangrove Forest from Above. An aerial view of the dense mangrove forest on Nusa Lembongan, Indonesia. © Joel Vodell

Extinction, Replacement, and the Myth of Ecological Wrongness

Extinction occupies a privileged moral position in conservation discourse, treated as the ultimate ecological harm. Yet extinction is neither anomalous nor avoidable; it is a fundamental mechanism of evolutionary change (Raup 1991; Jablonski 2004). Species that fail to adapt do not disappear suddenly but undergo prolonged decline characterized by starvation, disease, and reproductive failure.

From a systems perspective, artificially sustaining such species through intensive management may delay adaptation while prolonging suffering. Extinction is tragic from a human emotional standpoint, but it is not intrinsically wrong nor necessarily maladaptive at the ecosystem level.

Importantly, extinction does not signify emptiness but transition. Ecosystems respond through functional replacement, niche reconfiguration, and the emergence of new associations–processes observed repeatedly throughout deep time.

Biodiversity, Simplification, and Temporal Bias

Conservation biology frequently equates ecosystem health with high species richness. Yet many naturally occurring ecosystems are characterized by low visible diversity or monodominance, particularly during early successional stages or under extreme conditions.

Migrant species often simplify ecosystems initially, acting as structural or metabolic scaffolding upon which complexity can later emerge. Short-term declines in species richness may therefore reflect transitional dynamics rather than endpoints. The privileging of immediate diversity metrics reveals a temporal bias aligned with human observation cycles rather than ecological reality.

As Davis et al. (2011) argue, judging species by origin rather than effect obscures functional contributions and reinforces static conceptions of nature.

Moral Projection and the Illusion of Ecological Control

As far as we can perceive, nature does not possess moral categories. Concepts such as harm, value, and responsibility arise within human cognition and culture. Conservation biology often obscures this fact by presenting value-laden decisions as scientific imperatives.

The prioritization of native species reflects cultural nostalgia, aesthetic preference, and a desire for control rather than ecological necessity (Chew & Hamilton 2011; Sagoff 2005). Moreover, eradication campaigns justified in the name of conservation frequently involve large-scale killing and system disruption, raising ethical contradictions even within human moral frameworks.

A post-anthropocentric ecology does not deny human values but refuses to universalize them. It calls for ethical humility: recognizing that ecosystems do not require our permission to change, nor our correction to persist.

Toward a Post-Anthropocentric Ecological Framework

A post-anthropocentric ecology rests on several principles:

Function over origin; ecological roles matter more than historical nativeness.
Processes over states; ecosystems are defined by flows, not snapshots.
Deep time over immediacy; adaptation unfolds across evolutionary scales.
Restraint over control; intervention should be exceptional, not reflexive.
Trust over mastery; ecosystems possess adaptive intelligence exceeding human prediction.

This framework does not reject conservation but reframes it as facilitation rather than correction.

This perspective does not argue against conservation action per se, nor does it suggest that all species introductions are benign from a human perspective. In closed or evolutionarily naïve systems, or where extinction risk is acute and replacement processes are deemed unlikely, intervention may, on occasion, be justified. However, in open, heavily altered systems where historical conditions no longer exist, reflexive opposition to migrant species may increase ecological harm. Conservation, in such contexts, must shift from enforcing historical fidelity to supporting functional resilience.

Conclusion: Letting Living Systems Lead

The persistence of life across billions of years testifies to its capacity for self-organization, adaptation, and repair. Migrant species are not ecological errors but expressions of this adaptive intelligence operating under novel constraints.

Post-anthropocentric ecology asks not how ecosystems can be made to resemble the past, but how they are already responding to the present. In an era of rapid planetary change, the most ethical and ecologically grounded response may not be to intervene more aggressively, but to listen more carefully–to learn when healing is already underway, even if it does not look like what we expected.

Megan Bonnett
megan.bonnett@gmail.com

Benton, Michael J. 2009. “The Red Queen and the Court Jester: Species Diversity and the Role of Biotic and Abiotic Factors Through Time.” *Science* 323 (5915): 728–732. https://doi.org/10.1126/science.1157719.

Chew, Matthew K., and Andrew L. Hamilton. 2011. “The Rise and Fall of Biotic Nativeness: A Historical Perspective.” In *Fifty Years of Invasion Ecology: The Legacy of Charles Elton*, edited by David M. Richardson, 35–47. Chichester, UK: Wiley-Blackwell. https://doi.org/10.1002/9781444329988.ch4.

Davis, Mark A., Matthew K. Chew, Richard J. Hobbs, Ariel E. Lugo, John J. Ewel, Geerat J. Vermeij, James H. Brown, Michael L. Rosenzweig, Mark R. Gardener, Scott P. Carroll, Ken Thompson, Steward T. A. Pickett, Juliet C. Stromberg, Peter Del Tredici, Katharine N. Suding, Joan G. Ehrenfeld, J. Philip Grime, Joseph Mascaro, and John C. Briggs. 2011. “Don’t Judge Species on Their Origins.” *Nature* 474 (7360): 153–154. https://doi.org/10.1038/474153a.

Hobbs, Richard J., Salvatore Arico, James Aronson, Jill Baron, Peter Bridgewater, Valerie A. Cramer, Paul R. Epstein, John J. Ewel, Carlos A. Klink, Ariel E. Lugo, David Norton, Dennis Ojima, David M. Richardson, Eric W. Sanderson, Fernando Valladares, Montserrat Vila, Roger Zamora, and Michael Zobel. 2006. “Novel Ecosystems: Theoretical and Management Aspects of the New Ecological World Order.” *Global Ecology and Biogeography* 15 (1): 1–7. https://doi.org/10.1111/j.1466-822X.2006.00212.x.

Hobbs, Richard J., Eric S. Higgs, and Carol M. Hall, eds. 2013. *Novel Ecosystems: Intervening in the New Ecological World Order*. Chichester, UK: Wiley-Blackwell.

Holling, C. S. 1973. “Resilience and Stability of Ecological Systems.” *Annual Review of Ecology and Systematics* 4: 1–23. https://doi.org/10.1146/annurev.es.04.110173.000245.

Jablonski, David. 2004. “Extinction: Past and Present.” *Nature* 427: 589. https://doi.org/10.1038/427589a.

Lugo, Ariel E. 2004. “The Outcome of Alien Tree Invasions in Puerto Rico.” *Frontiers in Ecology and the Environment* 2 (5): 265–273.

Pickett, Steward T. A., and Peter S. White, eds. 1985. *The Ecology of Natural Disturbance and Patch Dynamics*. Orlando, FL: Academic Press.

Raup, David M. 1991. *Extinction: Bad Genes or Bad Luck?* New York: W. W. Norton.

Sagoff, Mark. 2005. “Do Non-Native Species Threaten the Natural Environment?” *Journal of Agricultural and Environmental Ethics* 18 (3): 215–236. https://doi.org/10.1007/s10806-005-1500-y.

Saintilan, Neil, Nicholas C. Wilson, Kerrylee Rogers, Anusha Rajkaran, and Ken W. Krauss. 2014. “Mangrove Expansion and Salt Marsh Decline at Mangrove Poleward Limits.” *Global Change Biology* 20 (1): 147–157. https://doi.org/10.1111/gcb.12341.

Shafroth, Patrick B., James R. Cleverly, Tom L. Dudley, John P. Taylor, Charles van Riper III, Edwin P. Weeks, and James N. Stuart. 2005. “Control of *Tamarix* in the Western United States: Implications for Water Salvage, Wildlife Use, and Riparian Restoration.” *Environmental Management* 35 (3): 231–246. https://doi.org/10.1007/s00267-004-0099-5.

Stromberg, Juliet C., Matthew K. Chew, Pamela L. Nagler, and Edward P. Glenn. 2009. “Changing Perceptions of Change: The Role of Scientists in *Tamarix* and River Management.” *Restoration Ecology* 17 (2): 177–186. https://doi.org/10.1111/j.1526-100X.2008.00514.x.

Wu, Jianguo, and Orie L. Loucks. 1995. “From Balance of Nature to Hierarchical Patch Dynamics: A Paradigm Shift in Ecology.” *The Quarterly Review of Biology* 70 (4): 439–466. https://doi.org/10.1086/419172.

Revising the Eradication Goals of Invasion Biology

It is my pleasure to publish (with permission) Arthur M. Shapiro’s (Professor of Ecology & Evolution Emeritus, UC Davis) review of Ecological Explosions: The History of Biological Invasion and Invasion Science, by Daniel Simberloff (Professor of Environmental Science, University of Tennessee).

Professor Simberloff is a prolific and vociferous adherent to the hypotheses of invasion biology, as well as to the related commitment to eradicating non-native plants. I heard Simberloff speak at the conference of the National Park Service, “Science for Parks, Parks for Science,” at UC Berkeley in 2015. It was a time when critics of invasion biology were emerging and becoming more vocal and visible. Simberloff called out by name Emma Marris, Peter Kareiva and others for their criticism of invasion biology.

In 2020, I heard Simberloff speak at the annual forum of the California Invasive Plant Council. His presentation was similar to his presentation in 2015 in that it was primarily focused on critics of invasion biology whom Simberloff calls “deniers.” Simberloff categorized the criticisms of invasion biology then flipped them off, one by one.

Then, Simberloff’s presentation took an unexpected turn when he was asked this question by the moderator: “Dan, you mention the “futility” argument, but what about the notion that the cost in environmental damage (e.g, pesticide use and nontarget impacts) is too high for some well-established invaders?” Simberloff’s answer to this question was surprising and encouraging to critics of pesticide use to kill non-native species:

“Absolutely, it’s a huge problem, not only on non-target species, but also the fact that evolution of resistance leads to greater use of pesticides before they are useful and leads to greater impact on non-target species. I didn’t talk about this, but yes, of course the cost both economically and ecologically might be too great even if management eradication is feasible. But that’s not what denialism is about. Denialism willfully denies that there are impacts or they confound arguments about values as if it is an argument about science.” Daniel Simberloff

Simberloff’s concern about the costs “both economically and ecologically” of eradicating non-native plants was as much a shock to the Executive Director of the California Invasive Plant Council–which actively champions the use of herbicides to eradicate non-native plants–as it was to me.

Based on that experience, I had a premonition that Simberloff’s recent publication might be another surprise and so it is, as Professor Shapiro explains in his review. Simberloff publishes this exhaustive tome at the age of 84. Perhaps it is his last word. It is a significant revision to the long crusade to eradicate every non-native plant.

One hopes Simberloff’s book will influence the “restoration” industry to be more circumspect when choosing their eradication targets and their methods. If so, it comes at a good time because every effort to reduce pesticide use in the US has been tried and failed.

Last week, the US Supreme Court overturned product liability lawsuits brought by users of glyphosate with cancer, because the Environmental Protection Agency does not consider glyphosate carcinogenic, though it indisputably is. EPA’s determination now over-rides any state determination to the contrary. Earlier, President Trump also signed an Executive Order, promoting the use of glyphosate and Robert F. Kennedy, Jr., Secretary of Health and Human Services, endorsed the Executive Order.

I am deeply grateful to Professor Shapiro for giving me this opportunity to publish his review of Professor Simberloff’s book about invasion biology. I am also grateful to Professor Simberloff for taking a closer look at the consequences of eradicating non-native plants.

Conservation Sense and Nonsense

REVIEW: ECOLOGICAL EXPLOSIONS: THE HISTORY OF BIOLOGICAL INVASIONS AND INVASION SCIENCE. Daniel Simberloff. University of Chicago Press. 2025. 729 pp.

I was fully prepared to detest this book—until I read it.

Dan Simberloff, as E.O. Wilson’s star graduate student at Harvard, was present at the creation of the theory of island biogeography, which used simple mathematical and graphical models to bring order to a vast heap of anecdotal information and in so doing radically transformed ecology—from natural history to analytical science (not everyone was thrilled). Simberloff’s subsequent career can be seen as the application of that approach to the implications of human-mediated changes in the geographic ranges of species generally. Now in his 80s, he has written this doorstop of a book as the envoi to his career. Why, I wondered, would anyone want to read it?

Simberloff and I are contemporaries. My undergrad adviser at Penn, Robert MacArthur, was Wilson’s collaborator on “The Theory of Island Biogeography,” and very much wanted me to do my Ph.D. with Wilson. MacArthur was under the illusion that I had mathematical talent, despite my best efforts to convince him otherwise. I knew it would be a bad fit, and to his frustration never even applied to Harvard. I went to Cornell for my degree, a place more in tune with a natural historian like me. I have often joked that had I gone to Harvard I would have become Dan Simberloff! Both Simberloff and I read Charles Elton’s “The Ecology of Invasions by Animals and Plants” (1958), the book that established invasion biology as a field and gave it its name. In Dan’s case reading that book shaped his entire career. It had many impacts on mine as well; I began observing and studying the adoption of naturalized host plants by native insects, mainly Lepidoptera, and it profoundly affected my teaching (community ecology, biogeography) for the next 50+ years. So it was natural that I, at least, would want to read it.

At the same time I had become disaffected with what I perceived as both the ideological and the faddish turn of invasion biology, and I was apprehensive about what I might find. I needn’t have been.

The first part of the book is a more-or-less chronological history of the development of invasion science, from the earliest observations of European weeds in New England by John Josselyn down to our own time. This is not a catalogue of case histories, but the ones selected are judiciously chosen to be representative of aspects of the field. Most were already familiar to me, but quite a few were not, even after more than five decades.

But the most important chapters for me were at the end. Chapter 18 (“Controversies Abound”) confronts head-on the conflation and entanglement of invasion biology on the one hand and xenophobia and racism on the other—exemplified by the term “native plant Nazis,” referring to those who advocate eradication of non-native species. The use of political and military metaphors (including the word “invasion” itself!) has contributed to such conflation and its undesirable resonances. The conflation has deep roots, which Simberloff explores—consider the New York socialite Madison Grant, a prominent lay conservationist, who authored the scurrilous racist tract “The Passing of the Great Race: or the racial basis of European history” (1916), by no means an isolated case. Simberloff has no patience for the blanket rejection of species solely on the basis of their “native” vs. “non-native” status. He recognizes that each case must be approached contextually and that there is no justification for eradication campaigns except in the most exigent circumstances (pathogens, parasites—the current alarm over the screwworm comes immediately to mind; invaders that pose grave risks to agriculture or to the survival of prized native species and ecosystems). Chapter 19, on the future of invasion science, elaborates on these themes in the context of a world that is changing at an ever-accelerating pace.

Do age and experience confer wisdom on us? Perhaps not inevitably. But this book convincingly demonstrates that they have done so for Dan Simberloff. If you are seriously interested in invasion biology, get and read this doorstop of an envoi: all 729 pages of it.

ARTHUR M. SHAPIRO

University of California, Davis

Eradication: A Fable

The hero of Eradication: A Fable (1) is Adi, a jazz musician and 4^th grade school teacher in an unnamed South American country. He has recently lost his 11-year old son, Jairo, who fell from the roof of their apartment building. Jairo was neuro-divergent, with an obsession with flying paper airplanes. Adi believes Jairo’s fall was accidental, but his wife believes he was pushed by neighborhood boys who habitually harassed Jairo. Adi’s wife, the daughter of a mob boss, insists that Adi kill the neighborhood boys in retribution. When Adi refuses, his wife leaves him. We understand that Adi is no killer.

Adi is bereft about the loss of his family when he notices an advertisement for a job that would send him to an uninhabited island in the Pacific Ocean for 6 weeks to “save the world.” This looks like an opportunity to heal his wounded soul in peace and quiet.

When Adi interviews for the position, he learns that the job is more complicated than camping on a tropical beach in solitude. The woman who interviews him works for a foundation (think Island Conservation) informs him that the job is to shoot and kill about 4,500 goats on the island. The foundation believes the goats are responsible for destroying vegetation on the island and causing rare animals to become extinct.

Goats are used to manage fuel loads in the San Francisco Bay Area and other places. This herd of several hundred goats was browsing trees, shrubs, and grass in an East Bay park in August 2025. They are eating poison oak that was fruiting with berries. Goats are the best way to reduce dry vegetation during our dry season. One of the disadvantages of using herbicides is that they must be used when the grass is green, which produces a flammable dry thatch. Herbicides increase fuel loads. Goats turn the vegetation into tidy pellets of goat poop.

Over one hundred years ago, a pair of goats had been dropped off by whalers at the beginning of their hunt, expecting to pick up more goats to provision their trip home. The goat population initially exploded to about 40,000, but eventually reached a balance with available resources with a stable population of 4,500.

Adi has never shot a gun, nor does he have any interest in learning how to. Although he is woefully unqualified for the job, he is hired because he is the only applicant.

Not a Fable

The scenario is not a fable in the sense that it is not fiction. It is based on actual island eradications that have been done all over the world for over 100 years.

Source: “The global contribution of invasive vertebrate eradication as a key island restoration tool”

A peer-reviewed study published in 2022 reported that 1,550 attempts to eradicate “invasive” vertebrates have been conducted around the world in the past 100 years. The study reports an average success rate of 88% for all vertebrate species. Eradication of ungulates (such as goats) was most successful at 96% and eradication of mice least successful at 73%. The number of eradication attempts increased significantly since the 1980s and peaked in the mid-2000s, according to this study.

In January 2024, the EPA announced the intention of Animal and Plant Health Inspection Service (APHIS) to conduct eradications using rodenticides on 29 islands in US waters in the subsequent 5-7 years. In the case of Hawaii, the list of planned projects says “all islands,” which could apply to 137 individual islands comprising the state of Hawaii. Many of the listed 29 islands are actually complexes of islands, such as those in Boston Harbor. Many of the islands are residential communities, such as Nantucket and Martha’s Vineyard.

The biological evaluation of rodenticides used in these projects was finalized (and made more dangerous by the removal of mitigation measures) in December 2024, shortly before the Trump administration took office. Funding for the agencies responsible for conducting these projects has been drastically reduced and the priorities of the administration favor resource use rather than resource conservation.

There is no public record of these 29 projects moving forward, with one exception. Island Conservation reported the completion of a rat eradication on Wake Atoll on April 14, 2026. As usual, Island Conservation reports a complete success of the recently completed project. The first eradication attempt on Wake Island in 2012 was a partial failure. It failed to eradicate the Pacific rat from Wake and Wilkes islands, allowing populations to rebound.

This is a typical scenario for island eradications. Island Conservation conducted the project in collaboration with US Fish & Wildlife Service and Department of Agriculture and Island Conservation is reporting its success. There is no independent monitor for the project. The public is not allowed to observe, nor do we have access to the island when the project is done. The success is reported shortly after completion of the project and there is no planned independent follow-up monitoring. In other words, the success rate is not credible.

Eradication IS a Fable

A dictionary definition of fable is “a short, fictional story—often featuring anthropomorphized animals, plants, or forces of nature—that teaches a clear moral lesson, typically ending with a concise maxim.” (Wikipedia) At a mere 159 pages, Eradication: A Fable meets the first criterion. What about the “clear moral lesson?” Let’s return to the story to look for a moral lesson.

In challenging physical conditions, Adi manages to kill two goats and wound a third. He feels responsible for killing the wounded goat and pursues him to finish the job. The steep, densely vegetated terrain takes him far afield, where he stumbles into the camp of two drug-addicted criminals who make a meager living selling shark fins that they illegally hack off sharks. (I recommend skipping the grisly description of how sharks die without their fins.)

After Adi observes the shark fin-thieves shooting goats on the hillside from their small boat offshore, as though it’s a shooting gallery at a county fair, he decides it’s time to go home. He has an epiphany. He is doing the same thing as these criminals. It’s not company he wants to be in.

When Adi decides to leave the island and its goats behind, he briefly considers claiming that a serious injury requires him to leave. Then he thinks better of it: “Or maybe he would tell them the truth: that the goats weren’t to blame for what’s become of Santa Flora. That all they had ever done was refuse to stop living. They’d eaten because they were hungry. They’d mated because life is something you pass down. They’d sung because it pleased them, to mark the island with their voices before etching it with their bones. They weren’t a plague or a malignant growth or any of his interviewer’s other fuming metaphors; they weren’t metaphors at all. They were goats, nothing more, and their only crime had been to keep growing where we’d planted them. Santa Flora’s degradation was as much mankind’s doing as if we’d crop dusted with gales of poison or leveled it with bombs or stacked its shores with condominiums. We’d ditched the goats here for our convenience, just as we’d dumped the trash washed up along the windward shore, then ignored them for a century and a half. You could slaughter every last goat but you couldn’t eradicate the truth.” (1)

Several plotlines are not mentioned in my review. There are charming encounters with goats who qualify as a charismatic species. However, the ethical principles articulated by our hero apply to all species, in my opinion. I hope you will read it.

Adi Speaks For Us

When invasion biology was “invented” in the 1950s it started an era of defining conservation as killing. The primary message of Conservation Sense and Nonsense and the clear moral lesson of Eradication is very simple: just stop the killing!

(1) Eradication: A Fable, Jonathan Miles, 2026.

Seeking Peace in Our Gardens

Garden Rant recently published an article by garden-writer, Marianne Willburn, defending gardeners who prefer a diverse garden over an exclusively native garden. This issue has been hotly debated for several decades, generating conflict in gardens and garden societies. These are places where people seek refuge from life’s many challenges. Some mourn the loss of peace in the garden and wish for a return to peaceful co-existence between gardeners regardless of which plants they prefer. As American politics have become increasingly polarized, all the more reason to foster peace in our gardens.

Conflicting Goals in the Garden

The primary goal of home gardeners was beauty prior to the advent of the native plant movement. As the saying goes, beauty is in the eye of the beholder, which is a way of saying everyone has their personal definition of beauty. In the garden, some prefer order and symmetry while others prefer naturalistic chaos and abundance.

The native plant movement brought an entirely different goal to the garden about 30 years ago. Native plant advocates want a garden that they believe will best serve the wildlife that lives in it, from the insects at the bottom of the food web, to the birds that eat insects and beyond, to the top of the food web. Beauty is not their goal. In fact, a beautiful garden is considered by some the antithesis of a native garden, judging by the gardens of some of my neighbors whose gardens look dead half the year in our Mediterranean climate that is without rain half the year.

Dictators in the Garden

Such different viewpoints about the purpose of our gardens could have lived peacefully side-by-side if native plant advocates had respected the opinions of cosmopolitan gardeners, but they didn’t.

To quote the Garden Rant article, the native plant movement “saddles everyman gardeners (whether they wished to grow Hemerocallis [daylilies] or fill a raised bed with herbs) with the burdens of past and present ecological damage to our planet, the saving of species from extinction, and the reversal of climate change.”

Source: Garden Rant image of media article

If you haven’t been on the receiving end of such a moralistic lecture from a native plant advocate, you may think that’s an exaggeration. Here are a few examples of such condescending lectures from native plant advocates about the obligations of gardeners to save the planet:

Gardens planted with non-native plants are “blooming wastelands where the flowers feed nobody at all.”
“The typical suburban yard is actually worse than a wasteland. It’s a death trap.”
Margaret Renkle, NY Times, March 28, 2021

“It turns out I’ve been filling my yard with a mix of ecological junk food and horticultural terrorists.”
“I’m sorry to say that if you have a typical urban or suburban landscape, your lawn and garden are also dooming the Earth.”
Dana Milbank becomes a native plant gardener, Washington Post, April 7, 2023

“’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.’”
Doug Tallamy, Washington Post, June 30, 2023

“…no other “don’t” has been shouted more loudly lately than the list of plants to avoid, the various nonnative, longtime nursery-industry standards that are now understood to cause environmental harm.”
Margaret Roach, NY Times, March 17, 2026

Such dire predictions of ecological collapse are overheard among neighbors, over garden fences, in garden society meetings, and in conferences of the California Invasive Plant Council and the California Native Plant Society. Articles with similar themes are found in garden magazines and in the publications of environmental organizations such as the Sierra Club and the Xerces Society.

If the extravagant claims of advocates about the superiority of native plants received the scrutiny and analysis they need, the native plant movement would not have the power and influence that it presently has. Now let’s turn a bright light on the claims of nativism in the natural world.

Debunking Nativist Myths

Nathan Lambstrom is a botanist and professional landscape designer who has given us an example of how nativist myths persist. He reports that Doug Tallamy supports his claim that insects require native plants by obscuring the many contributions non-native plants make to moths and butterflies. He manipulates his data set to hide the documented contributions of non-native plants, including plants considered “invasive.”

I was introduced to the nativist myth that native plants store more carbon than non-native plants nearly 20 years ago in an undergraduate ecology class at UC Berkeley. The University’s land manager who was responsible for destroying non-native trees on the University’s open space told the class that “carbon storage in non-native trees doesn’t count.” I was horrified that the class as well as the professor teaching the class accepted this nonsensical statement without comment. The truth is that both native and non-native plants and trees store carbon while they are alive that would otherwise be released into the atmosphere, contributing to climate change. As long as native plant advocates continue to demand the destruction of non-native plants and trees, they cannot claim that their projects reduce greenhouse gases that cause climate change.

Academic Ecologists Retreat from Invasion Biology

Recently, Thomas Christopher (one of Doug Tallamy’s co-authors and allies) interviewed James Hitchmough, a British ecologist on his Growing Greener podcast. The title of the podcast suggests that Mr. Hitchmough’s viewpoint “challenges the US Consensus” regarding the relative value to insects of natives compared to non-natives. Mr. Hitchmough’s response was that the claimed preference of insects for native plants was conventional wisdom among ecologists in the past, but that “when they did the [field] work, they changed their view.” He also said that the singular focus on the needs of lepidoptera skews the issues because lepidoptera are only 15% of all insects. Other taxa of insects have less restricted host plant preferences than lepidoptera.

That change in viewpoint has occurred among academic ecologists in the US, but continues to be resisted by many gardeners, such as Thomas Christopher. Professor Emeritus Juliet Stromberg recently published a book about her journey from her graduate education, which was deeply steeped in invasion biology, to her present viewpoint, based on decades of fieldwork and as expressed by the title of her book: The Unruly Wild: Embracing Ecological Change in the Southwest.

Stromberg’s book is representative of the opinions of many academic ecologists today. Change in nature is inevitable and it is usually both good and bad, from the perspective of other members of the ecological community and no matter the geographic origins of plants and animals. When judging the impact of new members of an ecological community, the most likely answer is “it depends.”

Endorsements of Stromberg’s book suggest that she is not alone in her realization of the value of introduced plants, which are adapted to the conditions humans have imposed on them:

“An erudite love story of nature in the American Southwest.”
Fred Pearce, author of The New Wild

“Stromberg has written a masterful treatise on why a knee-jerk response to eradicating nonnative plants is not just misguided but counterproductive.”
Dov F. Sax, co-editor of Species Invasions

“Julie Stromberg articulates, with personal knowledge and deep love, a new way to understand and care for a changing world.”
Erick Lundgren, University of Alberta, Canada

Climate change, human activities, and evolution force us to embrace ecological change. Juliet Stromberg helps us to face this reality without fear, but with hope that nature can continue to cope with the demands that humans have made of it. Our efforts to prevent change are futile and they often cause more damage than the environmental changes themselves.

Restoring Peace to Our Gardens

We encourage gardeners to restore peace to our gardens by respecting our cosmopolitan preferences in our gardens, as we respect the preference of others for native plants.

Obscuring the Contributions of Non-Native Plants

Conservation Sense and Nonsense spends an inordinate amount of time and energy responding to Doug Tallamy’s claim that insects are solely dependent on native plants because his publications are extremely influential with home gardeners and public land managers. A preference for native plants is not in itself a problem. The problem is that the preference results in massive efforts to eradicate non-native plants on public land, using herbicides, which poison the soil, killing life in the soil and making it difficult to grow anything.

When Tallamy’s first book, Bringing Nature Home, was published in 2007, he said that the absence of native plants would ultimately result in “ecological collapse” because insects are essential members of the food web. At the same time, Tallamy freely admitted that his theory was based on his anecdotal observations in his own garden, not on scientific evidence: “How do we know the actual extent to which our native insect generalists are eating alien plants? We don’t until we go into the field and see exactly what is eating what. Unfortunately, this important but simple task has been all but ignored so far.”

So began his research program, which was designed to prove his theory. In 2011, he reported the results of a study by a graduate student under his direction, which compared the amount of insect predation in six gardens with predominantly ornamental plants to six gardens with predominantly native plants. In a chapter in The New American Landscape he said of that study, “the most important result, however, was that there was no statistical difference in the amount of damage on either landscape type.” The graduate student found no evidence that insects ate more native plants than non-native plants. Yet, in the same book in which he reports the study of his graduate student, Professor Tallamy repeats his mantra: “…our wholesale replacement of native plant communities with disparate collections of plants from other parts of the world is pushing our local animals to the brink of extinction—and the ecosystems that sustain human societies to the edge of collapse.”

Today, Conservation Sense and Nonsense publishes an article by Nathan Lambstrom, which reports another example of how Tallamy’s publications obscure the value of non-native plants to insects and entire ecosystems: “Ignoring the contributions that introduced plants make towards supporting imperiled pollinators not only skews our perception of these plants, leading to the commonly held assumption that native plants are the only plants that support pollinators, it causes us to potentially ignore and possibly interfere with the positive contributions that many of these plants, even those labelled invasive, can make,” Nathan Lambstrom.

Nathan Lambstrom. Photo by Caitlin Lambstrom.

Nathan Lambstrom is a plant ecologist, horticulturist, and plant science educator living in Southern Rhode Island. He has a BA in Environmental Studies from the University of North Carolina and an MS in Plant Biology and Conservation from Northwestern University. In addition to teaching landscape professionals, members of the public, and undergraduate students, he is the owner of an ecological landcare company, Lambstrom Garden Ecology. His favorite plant today is bearberry.

Conservation Sense and Nonsense

Counting the Contributions of Non-Native Plants

Deciding what to plant is challenging at every scale, whether working in a home garden or creating a restoration plan. In addition to ensuring that the chosen species will thrive in the given environment, there is now a crisis facing pollinating insects and we should aim to include plants that will provide a high level of support to those insects in terms of food and habitat. The importance of native plants in providing that support is well-understood, but the contributions of introduced (non-native, naturalized) plants to supporting pollinating insects is significant, and we should not discount it.

One subgroup of pollinating insects, lepidopterans (butterflies and moths), often have specific needs: their larvae can often only consume a narrow subset of plant¹. These insects have co-evolved with these plants over the course of millennia and adapted to break down any toxic or anti-herbivory substances the plants may produce. This means that if the egg of a butterfly or moth hatches in an area absent of plants that it can use as a food source (or larval host plant), it will starve.

Fortunately for us (and the insects) primary research has given us better data to help inform these decisions, and also a better understanding of exactly how restricted some host preferences are.

Insects are often not confined to a single native plant species

There is some good news: most of the lepidopterans that need a specific group of plants to survive are limited not to a single species, but to a single genus, a few genera (the plural of genus), or an entire plant family. A good example of this is the Black Swallowtail Butterfly (Papilio polyxenes) native to much of eastern North America. The larvae of the Black Swallowtail feed almost exclusively on plants in family Apiaceae, the dill family². Historically this included mostly native perennials of wet meadows.

Following European invasion of the Americas and widespread introduction of plants from the Old World, intentional or otherwise, the most commonly encountered Apiaceae in most parts of the Black Swallowtail’s range are non-native garden herbs or naturalized plants (e.g. dill, parsley, fennel, and Queen Anne’s lace). Black Swallowtail larvae are able to recognize these plants as food because they are chemically similar to the native plants within Apiaceae that were their historic food source.

Those introduced (non-native, naturalized) plants have become so common they are now the primary host plants for Black Swallowtail larvae. In fact, in Massachusetts there have been no confirmed sightings of Black Swallowtail larvae feeding on native species in the Apiaceae family since 2007 (Stitcher 2013). This may sound like ecological catastrophe, but the abundance of introduced Apiaceae plants is actually good news for the butterfly and causes no harm to the native plants since they do not rely on larval feeding to set seed and reproduce. Information like this is important for gardeners and land managers to keep in mind when making decisions about what plants to keep or remove. Wholesale eradication of naturalized plants like fennel or Queen Anne’s lace could, counterproductively, have a detrimental impact on Black Swallowtail populations.

Which plants can feed the most insects?

The other bit of good news is that we now have access to more information than ever before about how many species of lepidopteran larvae these plants are capable of supporting. The most well-known papers on this subject come from entomologist Dr. Doug Tallamy, who has introduced the idea of pollinator gardening with native plants to a wide audience.

One of his earlier papers demonstrating the ecological value of native versus introduced plants is a meta-analysis that was published in the journal of Conservation Biology in 2009 titled “Rankin g Lepidopteran Use of Native Versus Introduced Plants.” Tallamy and a colleague analyzed thousands of available records of preferred food sources of lepidopteran larvae and concluded that native plants in eastern North America, and particularly native woody plants, support more native lepidopteran species on average than introduced plants or herbaceous plants generally.

We are fortunate to have access to this data, which allows us to make more informed selections and specifically choose those plants that are known to support the most native lepidopterans. The aforementioned paper has an associated dataset (available online), ranking how many native and introduced lepidopteran species use each genus as a host plant. I use this dataset frequently to guide plant selection decisions and encourage others to do so as well. It shows that many of our beloved woody species can support an amazing diversity of native insects: some genera like our oaks (Quercus), birches (Betula), and maples (Acer) support larvae of hundreds of species of butterflies and moths (Fig. 1).

Fig. 1 – top-ranking woody plants and the numbers of lepidopteran species that can use them as host plants.

A closer look at the data

In addition to the tremendous ecological support these plants can offer, there are two things of note in this table. First is that an introduced genus, Pyrus (pear), which has no native species in the region, supports over 100 native lepidopterans—more than some native genera.

Second, the data analysis used in the Tallamy paper may be obscuring the value of non-native plants. Since the data were collected only at the genus level (not the species level), it is impossible from this dataset to determine, for example, whether a native or introduced birch is supporting lepidopteran species, or whether there’s a difference between the two.

In the dataset, plant genera are categorized by origin. If a genus has only native species in the region, it is labeled “native;” if it has only introduced species, it is labeled “alien.” Genera that contain both native and introduced species (oaks, maples, birches, willows, and hundreds of others) are categorized as “both.” Many plant genera in our region include both native and introduced species, and many species that we consider invasive have very close native relatives.

For statistical analysis in the Tallamy paper, however, all genera with “both” native and introduced species were re-classified as “native” only (see the “origin for analysis” column in Fig. 1). The reasoning behind this is not clearly explained in the paper, but it does have significant implications for our interpretation of the findings.

What does this mean in practice?

Consider the barberries (genus Berberis), one of the most common plants labelled invasive on the east coast. This genus includes two introduced species which are quite common on forest edges in disturbed environments (B. thunbergii, B. vulgaris) and one rare native species that is restricted to southwest Virginia (B. canadensis) (Fig. 2).

Fig. 2 – county-level distributions of our three barberry species in eastern North America (adapted from BONAP)

When native lepidopteran larvae feed on non-native, naturalized barberry species (and 11 of them are known to do so), these observations get counted as “native” because the genus also contains a native species. The contribution of the introduced barberry to lepidopterans becomes invisible in the analysis (Fig. 3).

Fig. 3 – many of our most aundant “invasive” plants support dozens of native species of lepidopteran larvae

Another example, clovers (genus Trifolium), are known to support 115 native lepidopteran species. There are over a dozen non-native, naturalized clovers throughout the region (quite common in lawns and post-agricultural environments) and two uncommon native ones restricted to the southeast. Treating clovers (and any other genus that contains both native and introduced species) as native effectively erases the ecological contributions of introduced species to lepidopterans. For the purposes of the Tallamy paper, any time an insect uses an introduced plant from a genus that also contains native species, that positive interaction is credited solely to native plants.

A different story

When we separate out the data by actual plant origin, a more nuanced picture emerges (Fig. 4):

Native woody plants still perform better on average, supporting 64 lepidopteran species (61 native) compared to introduced woody plants supporting 49 species (46 native). The advantage exists, but it’s much smaller than the 14-fold difference reported in the original analysis.
For herbaceous plants, the native advantage disappears entirely. In fact, introduced herbaceous plants support more lepidopteran species on average: 6 species (5 native) for introduced plants versus 5 species (4 native) for native plants.

Fig. 4 – average number of lepidopteran species supported by origin and plant type

The widespread belief that native plants are always dramatically superior to introduced plants is not a reflection of ecological reality. By treating mixed origin genera as entirely native, the ecological value of thousands of introduced plant species is misattributed to native plants, concealing the introduced species’ actual contributions to pollinator support.

Land managers and gardeners using this research to guide their decisions may be removing introduced plants that are, in reality, providing significant support to native insects. When we aim to eradicate naturalized plants based on the assumption that only native plants matter, we may be eliminating valuable resources that insects have already incorporated into their life cycles.

Introduced plants are active participants in ecosystems

Ignoring the contributions that introduced plants make towards supporting imperiled pollinators not only skews our perception of these plants, leading to the commonly held assumption that native plants are the only plants that support pollinators, it causes us to potentially ignore and possibly interfere with the positive contributions that many of these plants, even those labelled invasive, can make.

Primary research has shown us many times that introduced plants, whether in a garden or naturalized in a landscape, can provide food in the form of nectar, pollen, and larval host plants to many of our native bees, wasps, butterflies, and moths (Sax et al. 2022). Not to mention the ecological value they can provide in terms of habitat, erosion control, carbon sequestration, bioremediation, etc.

We know that introduced clovers (Trifolium), in addition to their value as lepidopteran hosts, can serve as a valuable food source for native bumblebees (Harris and Ratnieks 2022). Common buckthorn (Rhamnus) is now the primary food source for an endangered butterfly, Henry’s Elfin (Cech and Tudor 2005). Many of the species that are considered some of the worst “invasives” in eastern North American are themselves able to host the larvae of many native lepidopteran species (see again Fig. 3). We ignore this at our peril in a changing climate.

Native plants are still important

These assertions should not be interpreted to mean that native plants do not matter. Whenever I teach on this subject, I always take pains to point out that native plants are extremely important. We should conserve them, plant them, propagate them, and appreciate them.

But the importance of native plants does not mean that introduced plants have no ecological value. Native plants are extremely important, and introduced plants have ecological value, too. While I find all of this information extremely useful, and use it to make plant selections, I am opposed, to some degree, to a utilitarian ranking of plants based solely on the number of insect species they can support. The natural world is incredibly nuanced and complex. Any overly binary system of understanding will never capture all of its beautiful, messy reality.

I believe every plant has value in its own right, and I still plant and appreciate plants, native or otherwise, that support few or no lepidopteran larvae. Many of our grasses (Bouteloua, Sporobolus, Koeleria), wildflowers (Chrysogonum, Eurybia, Vernonia), and even some of our woody trees and shrubs (Cladrastis, Eubotrys, Itea) support a whopping 0 species of lepidopteran larvae, either native or introduced.

I do not think that means those plants, or any other plant that supports very few pollinators, have no value or that we should ignore them entirely. But I do think we can use information like this to re-evaluate how plants that are often vilified are actually integrating into our ecosystems.

Fig.5 – native Virginia Tiger Moth larvae feeding on an invasive Ampelopsis (Porcelainberry) vine

Do not judge plants solely by their origins

This is a deeply fascinating and thorny topic, and the more we are able to view plant behavior with an eye towards their effects rather than their origins, we will be better stewards of the ecosystems that are under our care. I am hopeful that with more information and context we will all be able to make more informed decisions about the management of wild plants, and have a deeper appreciation of the complex, chaotic interplay of plants and animals that is always around us, native or introduced, but wild nonetheless.

Nathan Lambstrom, MS
nathan@gardenecology.us

References:

Cech, R., & Tudor, G. (2005). Butterflies of the East Coast: an observer’s guide. Princeton University Press.

Harris, C., & Ratnieks, F. L. (2022). Clover in agriculture: combined benefits for bees, environment, and farmer. Journal of Insect Conservation, 26(3), 339-357.

Sax, D. F., Schlaepfer, M. A., & Olden, J. D. (2022). Valuing the contributions of non-native species to people and nature. Trends in Ecology & Evolution, 37(12), 1058-1066.

Stitcher, S. (2013). Black Swallowtail Butterfly. The Butterflies of Massachusetts. https://www.butterfliesofmassachusetts.net/black-swallowtail.htm

Tallamy, D. W., & Shropshire, K. J. (2009). Ranking lepidopteran use of native versus introduced plants. Conservation Biology, 23(4), 941-947.

Addenda by Professor Emeritus Arthur M. Shapiro (UC Davis)

“Leps are hardly unique among insect groups in their degree of host specialization. Coleoptera (beetles) in particular have a great many host-plant specialists (Chrysomelidae and Cerambycidae in particular). Even Orthoptera have their share of host specialists:– the Post Oak Locust (Dendrotettix quercus) of the NJ Pine Barrens is a splendid example; it feeds only on Post Oak (Quercus stellata).”
“The Black Swallowtail is not confined to Apiaceous hosts. It also feeds on the chemically-similar Rue family (Rutaceae), including garden rue (Ruta graveolens) and in warm climates, members of the genus Citrus. I personally raised it on Ruta when I lived back east. Many tropical and subtropical members of the lineage feed on Citrus almost or exclusively, including the Papilio thoas-cresphontes group in the Americas and P. demoleus and P. demodocus in the Old World. Feeding on herbaceous Apiaceae is probably a fairly recent host range expansion for swallowtails (Miocene or Pliocene?).”

The Illusive Definition of “Invasive” Plant

Kollibri Terre Sonnenblume and his writing partner, Nikki Hill, are co-authoring a book tentatively entitled “Don’t Blame the Messenger: A critique of the ‘invasive plant’ narrative.” Kollibri has published a draft chapter of their book on his Substack, “Speaking for the Trees, No Matter Where They’re From.” The chapter is foundational to their book and serves as a teaser for the rest of the book. More chapters of the book will be available to paid subscribers of Kollibri’s Substack, “Speaking for the Trees.”

Many thanks to Kollibri and Nikki for this important contribution to our understanding of invasion biology as an ideology based on many conundrums and contradictions.

Conservation Sense and Nonsense

St. Johnswort. Photo by Kollibri Terre Sonnenblume

What is an “invasive” plant?

What is an “invasive” plant? Colloquially, some gardeners call any plant that thrives and spreads with little or no care “invasive.” They cast the term on both “weeds” and on ornamental nursery plants that have the temerity to spread outside their apportioned area. Such gardeners are seeking to uphold a particular aesthetic and their impulse to design and direct can yield results ranging from elegant to cloying. If this were the only way that people used the word, “invasive,” it would be harmless, and there would be no need for this book. However, the label is applied far beyond this narrow context.

Going to the dictionary for the meaning of “invasive,” Merriam-Webster provides: “relating to, or characterized by military aggression.” The Cambridge Dictionary defines “invade” as: “to enter a country by force with large numbers of soldiers in order to take possession of it; to enter a place in large numbers, usually when unwanted and in order to take possession or do damage; to enter an area of activity in a forceful and noticeable way.” For “invasive” it says: “moving into all areas of something and difficult to stop.”

That’s clear enough. But what is the official definition of an “invasive species,” whether plant or otherwise?

The short answer is that there is none.

The longer answer is that there are many definitions crafted by various policy-makers, non-governmental organizations and advocacy groups. Here are a few:

US federal government: “an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.”ⁱ
The United Nations Environmental Program: “introduced species that become established in a new environment, then proliferate and spread in ways that are destructive to human interests and natural systems.”ⁱⁱ
The International Union for Conservation of Nature (IUCN): “animals, plants or other organisms that are introduced by humans, either intentionally or accidentally, into places outside of their natural range, negatively impacting native biodiversity, ecosystem services or human economy and well-being.”ⁱⁱⁱ
Convention on Biological Diversity: “species whose introduction and/or spread outside their natural past or present distribution threatens biological diversity.”^iv

These definitions might seems straightforward at first glance, but a lot of ambiguity emerges as we unpack them.

The key words—“harm,” “destructive,” “negatively impacting,” “threatens”—beg the question of what constitutes “harm.” As we shall explore in this book, that’s not at all simple to answer in terms of ecological interactions. It’s even more difficult to identify what is “likely to cause” harm, as the feds put it. As invasion biologists have discovered, attempts to predict the results of species introductions based on the attributes of the species, for example, don’t have a very successful track record.

Also, if “harm” is being alleged then the possibility of benefit must also be admitted, a point completely ignored not just in these definitions but in most discussions or media coverage about “invasives.”

Economic concerns or “human interests” are named first by the US and UN, which might surprise people who think of the issue of “invasive” species as solely environmental. But commercial interests have had a strong hand in drafting the official policies that guide the “management” of “invasive” species. As we discuss in a later chapter, Monsanto and other nasty entities played a central role in the shaping US federal policy around “invasive species” because they profit from the sale of toxic pesticides used in their control. As for measuring the bottom line, one might assume that economic harm is readily quantifiable, but that’s also quite tricky, as we explain in the chapter “Lies, Damned Lies, and Statistics.”

“Alien” and “introduced” are synonyms for “non-native” (as are “exotic” and “non-indigenous”). The very concept of a “native plant” is a recent invention, though, and is another subject of contested deliberation, which we detail in “A Brief History of Invasion Biology.”

What is a fairly straightforward question in the Western Hemisphere—was it here before 1492?—is less clear in other regions. In the UK, some point to the Roman invasion of two millennia ago as the cut-off date (perhaps in part because that’s when bed bugs were introduced). In the case of Pacific islands like Hawai’i, some scientists designate species brought by Polynesians before the age of settler-colonialism as “non-native” but others limit it to European-introduced species. British colonization of the Australian continent commenced in 1788 (though the 1606 landing of a Dutch East India Company ship is the first documented European arrival) but some scholars label the dingo, introduced by Aboriginal people 4000 years ago, as non-native.

Political boundaries with no ecological significance can be a basis for defining nativeness, which also highlights the fact that nativeness is a scale-dependent factor. Tropical Milkweed (Asclepias curassavica) is native to North America from Mexico southwards but is called “invasive” in the United States (even though its pre-Columbian native range may have included southern Florida). Yet it’s also accurate to describe the species as “native to North America.” If a climate-induced, natural range shift of a species crosses the border of a country or a province will it be counted as non-native, but not otherwise?

Finally, how far does a species have to travel to be “out of range”? The endangered Monterey Cypress (Cupressus macrocarpa) is, according to journalist Andrew Cockburn, “a frequent target for the chain saws of the San Francisco Recreation and Parks Department—even though two small stands in Monterey, just fifty miles south, are cherished and protected as natives.”^v Meanwhile, a 500 mile drive north of its relict range, a large specimen planted by European settlers near Brookings, Oregon, in the 1850’s is an officially designated “Heritage Tree,” which we personally hope grants it safety because we’ve seen it and it’s majestic.

“Introduced” is shorthand for “introduced by humans either intentionally or accidentally.” It doesn’t include the actions of animals, weather, or other more-than-human agents in transporting species. It also doesn’t usually include indigenous humans, not because their own actions in moving around species haven’t been significant or are considered qualitatively different than those of settler-colonialists, but simply because they are generally not considered at all. This narrative omission is meaningful because it narrows the realm of possibilities for both human activity and human nature, a point we will be returning to in depth in later chapters.

In some cases, the non-native requirement has been dropped entirely. The State of New York includes the native Cup Plant (Silphium perfoliatum), on their “Prohibited and Regulated Invasive Plants” list because they characterize its growth as “aggressive.”^vi

This cursory sweep of these definitions demonstrates that we only need to scratch the surface of what is presented as a black and white issue to reveal a lot of gray area.

As we relate in detail later, similar accusations of “encroachment” by native flora are currently playing out with horrific results in the western US, where healthy woodlands of Pinyon-Juniper—declared a “native invasive” by some^vii—are being razed to expand rangeland for cattle.^viii

Further muddying the picture, the term “noxious weeds” is often used interchangeably with “invasive species” by organizations and individuals alike. The USDA has a list of “Introduced, Invasive, and Noxious Plants.”^ix The designation of “noxious weeds” is typically decided by local government entities in support of conventional farming and ranching, so a particular plant—native or introduced—will be added because of its purportedly negative effect on domesticated crops or animals. Thus, St. Johnswort (Hypericum perforatum) is bad because it can cause phototoxicity in sheep, Chervil (Anthriscus sylvestris) because it might carry a rust fungus that can affect cultivated carrot seed crops, and Pigweed (Amaranthus palmeri) because it grows in cornfields. Note that in the first two cases the plant or animal species supposedly threatened are themselves not native, and are products of a system—industrial agriculture—that is severely detrimental to the environment wherever it is practiced. Though Corn (Zea mays) is native, the ultra-hybridized and genetically-modified varieties grown today are so far from what indigenous people tended in Three Sisters arrangements that one could question if it’s even the same plant anymore. All three of these “weeds” also happen to be edible or medicinal for humans, so it’s a matter of priorities rather than usefulness that they’re slapped with a negative label and their eradication actively pursued. The primary motivation of noxious weed management is economic, not ecological—despite recent glosses of “sustainability” or “conservation” applied by some of its adherents—and more often than not involves pesticides.

What about science? How does invasion biology itself define “invasive?”

Scientists are well-known for disagreeing about definitions, and “invasive” is no exception. One biologist summed up the discussion by stating that there is “no indication that the field [will] be able to achieve uniformity in language in the near future.”^x

These are some of the concepts that have been used or proposed for “invasive”:

a species that successfully establishes itself in a new place
- such a species that establishes and has impact
  - such a species whose impact is negative
a species that, regardless of impact, establishes and spreads rapidly
a species that does any of the above which is non-native and introduced by humans
a species that does any of the above which is non-native, regardless of how it was introduced
a species that does any of the above which is native

These can’t all be true at once, obviously. There are too many contradictions. The science also suffers for dearth of agreement. One researcher noted that the “lack of consensus regarding the definition of invasive alien species (IAS) and vagueness around the demonstration of their impacts limits knowledge and research in this field.”^xi

Whether or not to use the word “invasive” at all is an ongoing debate in invasion biology. Historically, some scientists used the word “invade” and “colonize” to merely describe the movement of a species into a new area, or just the establishment of a species in a recently opened area, like after a fire, flood or landslide. But many scientists now recognize that, these days, the word has indisputably negative connotations which have implications not just within the field but for social discourse. Writes biologist Mark Davis, in his book, Invasion Biology:

I have never liked the term ‘invasion’ and think the field would have been much better off had it never been adopted, along with its accompanying military metaphors. Although the usage of military language may help to attract a group of highly motivated supporters, this same language may help foment a strongly confrontational approach, making it much more difficult to negotiate and resolve conflicts.^xii

More on the discussions within the field of invasion biology about terminology follow later.

A “confrontational approach” has certainly been a feature of too many discussions about introduced plant species. We have both been saddened to watch as native plant forums online, once a place to good-naturedly share photos and get IDs, have become toxic places where the word “invasive” is wielded like a club. Hateful rhetoric is the hallmark of dogma, not reason or thoughtfulness, and unfortunately it has been metastasizing in too many circles. We wonder how different the attitudes would be if “invasive” had never been used and we’d only ever had something neutral like “introduced” or nostalgic like “pioneer.”

**What’s not defined as “invasive” is just as important as what is**

Excluded from virtually everyone’s definition are the hundreds of non-native domesticated plants important to agriculture. This is highly significant given that over one fifth of the land in the lower 48 states of the US is cropland. That’s nearly 400 million acres of what was originally habitat for many, many native plant species. The excuse of “We need to eat!” doesn’t fly here; only 20% of that cropland is devoted to growing food directly for people; the majority of the remainder is for ethanol production, export industries, and livestock feed.^xiii

These stats should put the “invasive” dialogue into perspective. Picture the Midwest’s horizon-to-horizon corn and soy crops, California’s vast rice fields and almond orchards, or Oregon’s expanses of grass seed. These monocrops of non-native plants displaced prairies, forests and wetlands brimming with native flora and fauna. They are maintained with toxic pesticides and fertilizers, unsustainable water use, heavy machinery, fossil fuels, and oppressive labor practices. They dominate more than just their local geographical footprint, sucking in resources from distant places. According to the “invasive plant” narrative, the only “invasives” in these abused landscapes are the weeds coming up in the ditches or between the rows, a perspective we find perverse.

Other exemptions apply to the “invasive” label. As the US Department of the Interior’s Invasive Species Advisory Committee points out: “Kentucky bluegrass would be considered an invasive species in Rocky Mountain National Park in Colorado, but considered non-invasive a mere 60 miles away at a golf course in Denver.”^xiv If anything is “invasive,” how is it not the golf course itself? In the arid Coachella Valley of southern California, over 140 irrigated golf courses represent the complete destruction of the desert habitats that they replaced, and are a significant draw on the region’s precious water.

The topic of golf courses leads us to another big omission: lawns, which in their emerald-green ideal are monocultures of non-native grass. If lawn grass were categorized as an irrigated crop in the US, it would be ranked number one in land area and water use.^xv Yet it is the Dandelion that sprouts up in the front yard that’s “invasive.”

The “invasive plant” narrative is not ultimately about logic or facts. It’s about beliefs and prejudices, so a more relevant question than, “What is the definition of an ‘invasive’ plant?” might be, “What is meant by ‘invasive’?” What does the word signify? From what cultural foundations does it spring and what narrative edifice does it help perpetuate? There’s the narrative—that some plants are bad because they’re foreign—and then there’s the why of the narrative, which we delve into in Part 3, “Culture.”

“Bad plant”

In sum, the term “invasive plant” is thrown around so carelessly these days that, in common usage, it doesn’t really mean anything beyond some vague notion of “bad plant.”

But there are no “bad plants.” There are just particular plants that particular people in particular places at particular times have considered undesirable for particular reasons. That’s a lot of particulars. Too many to brand a whole species of plant with a pejorative label like “invasive” or “noxious” as if that’s its entire, intrinsic nature. Does it make sense to weed a garden? Of course. But that’s no reason to elevate our subjective calls—useful as they might be in a particular place and particular time—to the level of a universal constant, and to manufacture an army of villains in doing so. That just encourages our own misguided tendencies and puts off the day when we resume healthy connection and relating with life on this planet.

A very real invasion commenced in 1492, and with it came what some Anishnaabe tradition-bearers call “invasive land-ethics,”^xvi a concept we explain in “Introduced Plants, Settler-Colonialism, Indigenous Perspectives and Decolonization.” These ethics drove the cutting of forests, draining of wetlands, mining of mountains, plowing of prairies, damming of rivers, and slaughter to near extinction of Buffalo, Prairie Dogs, Beavers, Bears, Cougars and Wolves. These misbegotten ethics are unequivocally real and are active threats to the planet’s environment. Without addressing them, the destruction will only worsen.

In the meantime, the “management” of “invasive plants” routinely has its own negative effects, which we detail in the next chapter.

Kollibri Terre Sonnenblume

Citations:

iExecutive Order 13112 – Section 1. Definitions, February 3, 1999. https://www.invasivespeciesinfo.gov/executive-order-13112-section-1-definitions

iiUnited Nations Environmental Programme. “Invasive Alien Species—A grwoing threat in regional seas” https://wedocs.unep.org/bitstream/handle/20.500.11822/13623/invasive_alien_brochure.pdf

iiiIUCN. “Invasive Alien Species” https://www.iucn.org/our-work/topic/invasive-alien-species

ivConvention on Biological Diversity. “What are Invasive Alien Species?” https://www.cbd.int/invasive/WhatareIAS.shtml

vCockburn, Andrew. “Weed Whackers: Monsanto, glyphosate, and the war on invasive species” Harpers (September 2015). https://harpers.org/archive/2015/09/weed-whackers/

viNew York State Department of Environmental Conservation. NYCRR part 575 Invasive Species Regulation. (September, 2014). https://www.dec.ny.gov/docs/lands_forests_pdf/isprohibitedplants2.pdf.

viiAnsley, R. “Managing Native Invasive Juniper Species Using Fire” Weed Technology 19 (Jul 2005):517-522 DO – 10.1614/WT-04-098R1.1 http://www.bioone.org/doi/abs/10.1614.

viiiFite, Katie. “The Terrible Destruction of Pinyon-Juniper Forests” Counterpunch (December 28, 2018). https://www.counterpunch.org/2018/12/28/the-terrible-destruction-of-pinyon-juniper-forests/.

ixUSDA https://plantsorig.sc.egov.usda.gov/java/noxious?rptType=Federal

xDavis, Mark. “Invasion Biology.” (New York: Oxford University Press, 2009), p. 3.

xiFachinello MC, Romero JHC, Chiba de Castro WA (2022) Defining invasive species and demonstrating impacts of biological invasions: a scientometric analysis of studies on invasive alien plants in Brazil over the past 20 years. In: Giannetto D, Piria M, Tarkan AS, Zięba G (Eds) Recent advancements in the risk screening of freshwater and terrestrial non-native species. NeoBiota 76: 13–24. https://doi.org/10.3897/neobiota.76.85881

xiiDavis, 2009.

xiiiMerrill, Dave and Leatherby, Lauren. “Here’s How America Uses Its Land” (Bloomberg, July 31, 2018). https://www.bloomberg.com/graphics/2018-us-land-use/.

xivUS Department of the Interior Invasive Species Advisory Committee. “Invasive Species Definition Clarification and Guidance” April 27, 2006, p. 3. https://www.doi.gov/sites/doi.gov/files/uploads/isac_definitions_white_paper_rev.pdf.

xvCristina, Milesi & Elvidge, Christopher & C, J. & D, B. & Nemani, Ramakrishna & E, S.. (2012). A strategy for Mapping and Modeling the Ecological Effects of US Lawns.

xviReo, Nicholas J., Ogden, Laura A. “Anishnaabe Aki: an indigenous perspective on the global threat of invasive species,” Sustainability Science (2018) 13: 1443-1452. https://doi.org/10.1007/s11625-018-0571-4.

Environmentalism in the Rear-View Mirror

One year ago, less than a month after Donald Trump was re-elected President, I announced on Conservation Sense and Nonsense my intention to “hunker down and watch the changes [in the federal government] play out.” Although I predicted major changes in federal public policies, I did not foresee the scale and speed of changes in environmental policies that we have witnessed in the past year. The uncomfortable reality is that some of what is being destroyed deserved to be destroyed, but at the expense of some valuable environmental protections.

In describing the changes we have witnessed, I will focus primarily on environmental issues in the following main categories. Please keep in mind that changes in environmental policies are but a small fraction of the changes that have occurred in all aspects of American life and global geopolitics, e.g., education, public health, arts and entertainment, architecture, science, economics, immigration, media sources, judicial system, disaster relief, social safety net, foreign aid, tariffs, etc.

Policy intended to protect endangered plants and animals, included “loss of habitat” as one of the harms that recovery plans must mitigate. “Harm” is now defined by the Endangered Species Act narrowly as only harm directly to the endangered plant or animal. The Trump administration has also proposed significant new limitations on the application of the Endangered Species Act that will remove obstacles to resource extraction that will have a negative impact on endangered wildlife.
Federal agencies that were responsible for protecting the environment in the past have been defunded and their staff drastically reduced. The President calls them “Democrat agencies.” National parks, wildlife refuges and marine sanctuaries have lost both their funding and much of their staff. Places that were protected from unfettered resource extraction, no longer are.
Manufacturers of pesticides are lobbying Congress to prevent product liability lawsuits filed by people who have been harmed by pesticides. Congress is trying to prevent states from regulating the use of pesticides. Supporters of Robert F. Kennedy, Jr. are disappointed that Health and Human Services will not attempt to limit the use of pesticides in the US.
Laws and agency regulations that enabled the protection of the environment, the proverbial teeth in environmental policies, are being repealed:
- USFWS is in the process or rescinding the Roadless Rule, which prohibited new road construction in 60 million acres of national forests since 2001, enabling the expansion of timber operations.
- Bureau of Land Management is rescinding a policy that included conservation as one of many official uses of BLM land.
- Policy intended to protect endangered plants and animals, included “loss of habitat” as one of the harms that recovery plans must mitigate. “Harm” is now defined by the Endangered Species Act narrowly as only harm directly to the endangered plant or animal. The Trump administration has also proposed significant new limitations on the application of the Endangered Species Act that will remove obstacles to resource extraction that will have a negative impact on endangered wildlife.
- The Trump administration has proposed a significant limit on the EPA’s authority to limit pollution in wetlands, rivers and other bodies of water across the country: “These changes could strip federal protections from up to 55 million acres of wetlands, or about 85 percent of all wetlands nationwide, according to the Natural Resources Defense Council…”
- All efforts to reduce greenhouse gas emissions causing climate change have been abandoned. The President made good on his campaign promise to “drill, baby drill.” New commitments have been made to increase oil and gas extraction, as well as coal mining, off-shore drilling, and seabed mining. Corresponding new policies have eliminated commitments to develop renewable energy sources, such as wind and solar. The Environmental Protection Agency is promising to erase the endangerment finding that underpins climate regulations nationwide. The endangerment finding established that greenhouse gases endanger public health and must therefore be regulated to protect the public.

The Trump administration has left the international Paris Agreement, the legally binding treaty adopted in 2015 to limit global warming to below 2 degrees Celsius. The US was not represented at the November 2025 meeting of the UN Conference of the Parties (COP30) to the agreement in Brazil, but the US actively campaigned against the new commitment on the agenda to limit pollution from cargo ships by using fines. According to the New York Times, “…the United States launched a pressure campaign that officials around the world have called extraordinary, even by the standards of the Trump administration’s combativeness, according to nine diplomats on its receiving end.” US diplomats and officials were successful in threatening countries with loss of US port access and other onerous penalties if they voted for the proposal. The Trump administration hasn’t just dropped out of the Paris Agreement. It is also actively engaged in preventing other countries from reducing greenhouse gas emissions that cause climate change. COP30 ended without any new commitments to reduce the sources of greenhouse gas emissions, or even explicit mention of fossil fuels as the primary greenhouse gas.

America Accommodates

Many of these changes have been delayed by legal challenges, but until appeals reach the Supreme Court, the final verdict on most issues is not known at this time. However, the Supreme Court has signaled their intentions with many emergency orders, also known as the shadow docket. These decisions have upheld most of the federal government’s actions, without providing any legal reasoning for doing so. These preliminary decisions foretell the ultimate victory of the actions of the Trump administration.

Other segments of American society are contributing to the control the President has over the implementation of his agenda. At his request, Congress has completely defunded National Public Radio and the Public Broadcasting Service. They are scrambling to find other sources of revenue, while cutting programs and staff as well as closing stations. Associated Press was banned from White House press briefings when they refused to call the Gulf of Mexico the Gulf of America, as renamed by President Trump. Legal challenges have not restored AP’s access to White House press briefings.

Mainstream media has paid multi-million dollar settlements to resolve defamation lawsuits (ABC and CBS) brought by President Trump over perceived slights. One major network (CBS) has changed ownership and is now owned by Trump supporters (Larry & David Ellison). The Department of Defense (now calling itself the Department of War) has restricted access of the press to department staff and now requires department approval of press releases prior to publication. Most members of the Pentagon press corps refused to agree to these restrictions and have left their offices in the Pentagon. Self-censorship is a more insidious threat because the public no longer knows when the media is pulling its punches to avoid retribution, which is the President’s modus operandi.

The legal profession has also been brought to its knees by the President’s threats of punishment if they participate in lawsuits that try to prevent the implementation of the administration’s policies. Many major law practices have been forced to provide pro bono legal services for President Trump after being threatened with access restrictions to the judicial system. Major law practices are refusing to represent plaintiffs who are trying to protect themselves from government prosecution, hoping to stay out of the line of fire.

California Responds

The same day that Americans re-elected Donald Trump in November 2024, California voters passed Proposition 4 , the $10 billion bond that funds climate change mitigation and ecological restoration in California. California’s bond funding will help to compensate for the loss of federal funding of ecological and climate mitigation projects in California. California Natural Resources Agency reported the cancellation of federal funding for these projects in California:

Source: California Natural Resources Agency, July 2025

Does California have enough money to compensate for the loss of federal funding of climate change mitigation and ecological restoration in California? I don’t know, but I do know that federal funding is also being lost for many other purposes that are important to Californians, such as subsidies for health insurance and food assistance needed by many Californians. Some municipalities are responding by raising sales and property taxes to backfill the loss of federal funding in many sectors of the economy. While federal taxes are being cut, California’s taxes may rise.

Meanwhile, California is challenged by related issues such as the need to build more housing in order to reduce the cost and house our growing homeless population. In July 2025, California responded to that issue by revising the California Environmental Quality Act (CEQA), which will remove many obstacles to building new housing and allow more aggressive fire hazard mitigation.

The cost of gas in California has been consistently higher than in most states because of voters’ desire for clean air. Regulations have made drilling for and refining oil in California costlier than in other states, which makes gas more expensive for consumers. Refineries have responded to California’s restrictive regulations by leaving the state, which reduces supply, raises prices further and is expected to restrict availability of fuel. California’s Senate Bill 237, signed into law in September 2025, addressed these concerns by streamlining approval of drilling permits, including idle pipelines, in an “environmentally responsible and safe manner.”

In other words, California has been forced to adapt to new economic and environmental realities. At the same time, California is aggressively fighting back. As of October 1^st, California has filed 46 lawsuits against the 2^nd Trump administration, “contesting the Trump administration’s executive orders, agency decisions and even recent laws that Trump himself signed.”

Americans Shrug

Composite opinion polls reported a persistent negative approval rating of 11% for the Trump presidency until the government shutdown in October, when the approval rating dropped to negative 15% before returning to negative 11% when the government re-opened. Over 40% of American voters still approve of the Trump presidency. Many voters have made up their mind and are not responsive to the daily onslaught of alarming information. I understand and am sympathetic to the public’s dilemma, summarized in a recent social media post: “My desire to be well informed is presently at odds with my desire to remain sane.”

For perspective, consider that President Biden’s composite approval poll on July 6, 2024 was negative 19.3%, just 15 days before Biden dropped out of the presidential race on July 21, 2024.

The demonstrations I have attended are another window into the mood of the American public. The NO Kings demonstration on June 14, 2025 is said to have drawn 5 million people. The second NO Kings demonstration on October 18^th claims to have drawn 7 million people. Although these seem impressive numbers, they don’t add up to a change-making revolt. The lack of young people participating in these demonstrations is dispiriting. The future is in their hands, yet their commitment to democracy is lukewarm compared to my generation, the boomer generation that still feels a strong commitment to the peace and prosperity that democracy has delivered to us.

On the other hand, Democrats aren’t dead yet. In November 2025, moderate Democrats won governorships in New Jersey and Virginia and a Democratic Socialist won the mayoral election in New York City. In response to Republican gerrymandering of congressional districts in Texas, 64% of Californians voted to gerrymander congressional districts in favor of Democratic candidates. A recent Marist poll indicated that registered voters in the US plan to vote for Democratic candidates for congressional seats in 2026 by a margin of 14%.

Changes in the elected leadership of the Bay Area chapters of the Sierra Club are an indication of a change in the public’s commitment to the environment. The San Francisco Bay Area Chapter is now led by activists who want more housing and more active recreational opportunities. The old guard, who were committed to restricting recreational access in favor of native plant restorations in public parks, has been replaced. The Lomo Prieta Chapter, which represents the South Bay, is now undergoing a similar transition to new leadership with new priorities.

Changes in the leadership of the San Francisco Bay Area chapters of the Sierra Club are symptomatic of the Club’s much broader decline on a national scale. According to the New York Times, the Club has lost 60% of the 4 million members it had in 2019. The Times attributes this loss of support to the change of the Club’s advocacy focus from environmental issues, most prominently climate change, to progressive social justice issues such as racial justice, gay rights, labor rights, and immigration rights. In 2019, one of the Board Directors objected to the proposed budget, but was voted down: “I said, ‘We have two F.T.E.s devoted to Trump’s war on the Arctic refuge, and we have 108 going to D.E.I., and I don’t think we have our priorities straight,’” Mr. Dougherty said.

Finally, wealthy American philanthropists are providing clues of a fundamental change in the political climate in America. Bill Gates, former owner of Microsoft and supporter of global health initiatives, recently announced that it is time for a “strategic pivot” in the global climate fight from focusing on limiting rising temperatures to fighting poverty and preventing disease. Gates still believes climate change is a serious problem, but it won’t be the end of civilization because he thinks scientific innovation will contain it. Unfortunately, federal support for finding such scientific innovations has been withdrawn. Gates’ message seems to be that we aren’t able to stop climate change, so we must cope with it. It’s another way of accommodating the environmental policies of the Trump administration.

Looking Ahead

I am deeply troubled by the many threats to America’s treasured democracy. However, many of the changes in environmental policies in the past year are aligned with the mission of Conservation Sense and Nonsense. Since its inception in 2010, the mission of Conservation Sense and Nonsense has been the preservation of our predominantly non-native urban forest, opposition to the use of pesticides on public lands and advocacy for mitigating the causes of climate change. Some of the changes in environmental policy in the past year are consistent with those goals:

Many projects that use pesticides and kill harmless animals and vegetation have been defunded by the federal government. The State of California is trying to compensate for the loss with state funding, but its ability to do so will be challenged by many other new demands on state resources, such as subsidies for health care and food.

When wildlife refuges and marine sanctuaries lost much of their funding and staff, many of their projects were abandoned. Many of those projects may have been beneficial, but the plans to aerially drop rodenticides on the Farallon Islands to kill harmless mice is an example of a project that is better off dead.

Prevailing public opinion that native plants and animals are superior and the corresponding belief that non-natives are a threat to them is unlikely to change in the near-term. I do not begrudge the horticultural preferences of home gardeners. However, native plant advocates will have limited ability to demand that public land managers eradicate non-native plants if there is no public money available to fund landscape-scale “restorations.”
As public money for ecological “restorations” on public land dries up, the “restoration” industry and the jobs it creates will probably dwindle over time. As economic interests in “restoration” evaporate, the advocacy that supports it is likely to as well. College students are likely to make other educational choices with more promising career prospects, which will further reduce the labor force engaged in “restorations.”
When forest “restoration” projects that involve clear-cutting or removing healthy trees are defunded, existing carbon storage is preserved. Every mature tree—native or non-native—sequesters carbon at a time when we need every available carbon sink to compensate for the loss of limits on greenhouse gas emissions causing climate change.
Climate change will accelerate as we abandon our efforts to reduce greenhouse gas emissions that cause climate change. The landscape that survives the changed climate will be best adapted to the changed environment. When the climate changes, vegetation changes or dies. No amount of human intervention can alter that ultimate reality because nature always bats last.

In 2026, Conservation Sense and Nonsense will continue to report major developments relevant to my mission. In other words, I will continue to “hunker down and watch it play out.” Guest posts consistent with my mission and civil comments, both pro and con, are always welcome here. Thank you for your readership.

Happy Holidays and best wishes for a more peaceful year in 2026.

“Instead of ‘controlling’ non-native plants, perhaps we should practice more ‘self-control’”

Julian Burgoff wrote a guest post for Conservation Sense and Nonsense about the undervalued functions of non-native aquatic plants in 2023. Necessary Nuisance explained that non-native aquatic plants perform valuable ecological functions. Attempts to eradicate aquatic plants deprive aquatic animals of valuable habitat. The herbicides used to kill aquatic plants also pollute the water, harming aquatic animals and killing non-target aquatic plants.

Julian Burgoff is an avid bass angler and aspiring fisheries ecologist from western Massachusetts. He recently received a master’s degree with the Massachusetts Cooperative Fish and Wildlife Research Unit at UMass- Amherst where he studied juvenile river herring growth, diets and habitat use in coastal Massachusetts lakes and estuaries. He is passionate about lake ecology and the management of aquatic vegetation in lakes and hopes to work in a field related to lake conservation and warmwater fisheries management in the future.

I am grateful to Julian for giving us another opportunity to publish an article about a specific project that is trying to kill valuable aquatic plants with herbicides. Thank you, Julian.

Conservation Sense and Nonsense

Hydrilla and the Connecticut River: Falling into the “Invasive” Trap

If you spend time on the tidal Connecticut River in summer, you will likely see thick green mats covering its shorelines, coves and backwaters. This is hydrilla — a non-native aquatic plant that’s long been demonized by state agencies and lake managers across the country.

One morning during a summer internship performing fisheries related fieldwork on the river, I saw a young doe on the bank nibbling on a clump of hydrilla exposed at low tide. I laughed to myself — I knew it was good fish habitat, but even deer like the stuff!

The “official” position was that it was choking the river, outcompeting native species, and impeding recreational use of the river. But as a passionate angler and ecologist who studies aquatic ecosystems, I’ve learned that what we (as western scientists) think about non-native species and their impacts — especially in the world of aquatic plants — often turns out to be driven more by ideology than by scientific evidence.

The War on Hydrilla

Hydrilla arrived in the Connecticut River around 2016 and has since spread through the lower mainstem and its tributaries. In response, the Connecticut Agricultural Experiment Station (CAES) and the U.S. Army Corps of Engineers (USACE) have launched an aggressive herbicide campaign that seeks to “restore” native aquatic plant communities and study the efficacy of using a cocktail of various herbicides to treat the areas of the river where the growth of hydrilla is most prolific. Over the past few summers and into next year, private contractors plan to treat hundreds of acres of river coves with a mix of chemicals, including diquat and florpyrauxifen-benzyl.

On paper, this might sound like responsible ecological stewardship — reducing non-native plant stands such that their native counterparts can flourish. But in my view, it’s another example of what resource managers in Minnesota have referred to as “the invasive trap”: the belief that any non-native species must be “harmful”, and that launching management campaigns to kill them must be ecologically and economically beneficial.

The problem is that this assumption is not based on data, but on the dogmatic assumptions of invasion biology that underpin the world view of many western scientists and management agencies.

Unexpected Ecosystem Services: What the Evidence Shows

Across the country, hydrilla has often played the opposite role of what managers might expect. In the Chesapeake Bay and its tributaries, researchers found that hydrilla helped stabilize sediments, clear up murky water, and create habitat for fish and invertebrates — even helping native aquatic plant stands return. In Florida lakes, scientists compared lakes with and without hydrilla and found no major differences in fish, bird, or aquatic plant diversity.

In other words, hydrilla didn’t destroy these ecosystems where it was introduced. It filled open niche space, performed valuable ecosystem services, and is now integrated into the food web, for better or for worse.

That’s not to say hydrilla should be introduced to new water bodies or can’t impact ecosystems in ways that are perceived as harmful. Like many aquatic plants (native and non-native), hydrilla can grow in thick stands that interfere with swimming or boating, alter water chemistry and change physical habitat suitability for aquatic organisms. But many of these impacts are human nuisances, not ecological disasters, and should be managed as such. In large, dynamic systems like the Connecticut River, hydrilla’s role is likely far more complex — and possibly beneficial — than its label as “one of the world’s most invasive aquatic plants” suggests.

The Risks of Herbicide Use to “Restore” Native Plant Communities

Despite the lack of evidence that hydrilla is causing ecological “harm” to the Connecticut River, the proposed management intervention — widespread herbicide use — carries significant ecological risk.

Diquat, one of the main herbicides being applied, is what’s called a contact herbicide: it kills whatever plant tissue it touches (including native plant taxa). Florpyrauxifen-benzyl is a systemic herbicide, meaning it’s absorbed into plants and disrupts their growth. When a large quantity of aquatic plants rapidly die, they decay and release nutrients into the water, which can fuel algal blooms that reduce water clarity. If water clarity is significantly reduced, the very native plants managers aim to “restore” can’t regrow.

Ironically, hydrilla often bounces back first because it’s more tolerant of poor water quality than many native species. This can lock managers into a costly, never-ending cycle: herbicide use → temporary die-off → algal bloom → hydrilla regrowth → more herbicides.

Similar outcomes have been observed in Florida, where researchers found a large-scale florpyrauxifen-benzyl treatment sharply reduced hydrilla abundance in a Florida lake, but the plant regained dominance within a year as reduced water clarity from the treatment hindered native plant recovery.

Cascading Food Web Effects

As primary producers, aquatic plants are essential to the foundation of food webs — sheltering young fish, providing surfaces for invertebrates to live, and supporting wildlife like waterfowl. When herbicides are used to kill aquatic plants, there are often complex indirect impacts to the integrity of aquatic food webs.

Diquat is known to be toxic to not just plants (native and non-native) but invertebrates (the tiny animals that feed fish), such as amphipods. Even at concentrations lower than what’s used in field applications, diquat has the potential to impact these organisms which in turn may reduce available habitat for organisms higher up the food web like fishes.

Diquat also contains bromide, a compound that researchers have linked to a neurological disease killing bald eagles in the southeastern U.S. The disease develops when a particular cyanobacteria grows on hydrilla plants and interacts with bromide — forming a toxin that bio-magnifies as it moves up the food web. Ducks eat the hydrilla, eagles eat the ducks, and the toxin accumulates, damaging the eagles’ brains.

While this phenomenon hasn’t yet been documented in the Connecticut River, applying bromide-based herbicides in a manner that is likely to contribute to algal blooms (including cyanobacteria blooms) is not an ecologically sound management practice.

What We Don’t Know

Despite the confidence behind these large-scale management interventions, there’s little data showing how hydrilla has actually affected biodiversity or water quality in the Connecticut River. To prove that hydrilla is causing ecological “harm”, we’d need long-term monitoring — decades of data on aquatic plants, fish, wildlife, and water quality — collected before and after hydrilla became established. These data likely don’t exist at the scale needed to make an informed, unbiased assessment. Yet herbicide applications in the name of ecological “restoration” are moving forward anyway. The “post-monitoring” required by the project plan mostly focuses on the “efficacy” of the treatment (e.g. how much hydrilla biomass is reduced) not on whether algae blooms occur or how invertebrate and fish communities are affected.

This is a common phenomenon with herbicide treatments: the indirect effects of the management intervention are simply too complex and too costly to quantify. Based on the current “post-monitoring” protocol, if it’s found that hydrilla biomass is reduced and that native aquatic plant communities continue to exist following treatment, the project will be considered a success.

Less is More: Observation Based Management

Sometimes, the most ecologically mindful (and most cost effective) management decision is to pause to let species interactions occur unmolested and find their own equilibrium rather than impose an imaginary concept of what a given ecological community “should” be.

Where hydrilla interferes directly with human activities — say, blocking a boat ramp or clogging a marina — mechanical removal or small, targeted herbicide treatments could be reasonable management interventions. But broad, river-wide herbicide use is neither justified by science nor a long-term sustainable solution to non-native aquatic plant management.

With non-native species introductions, the truth is that there is no going back. Climate change, nutrient loading, and decades of physical habitat alteration via damming etc. have already changed this river beyond what it was a few centuries ago. Plants and animals are constantly being introduced and adapting to a new reality — one where species origins and “native” vs. “non-native” status matter far less than their role in maintaining ecosystem functions.

Rather than pouring more chemicals into the water, perhaps we should pour our efforts into observing, monitoring, and trying to understand why certain plants succeed and how ecosystems adjust to change over time. Instead of “controlling” non-native plants, perhaps we should practice more “self-control” and let nature heal itself without the imposition of the human ego and its desire to constantly fight the expressions of the natural world in the Anthropocene.

Julian Burgoff
Amherst, MA
jburgoff@umass.edu

Ideological vs. Scientific Definition of Biodiversity

Although there is broad agreement that maintaining biodiversity is necessary to achieve conservation goals, there is disagreement about the definition of biodiversity. Some native plant advocates believe biodiversity includes only native plants (example HERE). Most scientists include both native and non-native plants in measurements of biodiversity. I asked Claude.ai about this debate.

Data source: Living Planet Report (2022). World Wildlife Fund (WWF) and Zoological Society of London.

I publish Claude.ai’s answer to my question as a guest post today. Claude.ai now has immediate access to internet sources, which makes answers to such queries more current and comprehensive. Claude.ai has also provided links to the sources of the information provided.

Conservation Sense and Nonsense

The ongoing debate about measuring biodiversity

Claude.ai: Based on the available data, there’s a significant and ongoing scientific debate about whether biodiversity measurements should include non-native species. Here’s what the evidence shows:

Scientific Practice vs. Conservation Ideology

The Reality of Scientific Measurement:

In actual scientific practice, major biodiversity databases and assessment tools often do include non-native species. Research shows that “data used for biodiversity assessments and conservation planning should, initially, include all species” and that “including non-native species into the Biodiversity Intactness Index can lead to a 10% improvement in the index score” NihNCBI.

The Global Biodiversity Information Facility (GBIF), one of the world’s largest biodiversity databases, explicitly includes non-native species, stating that “information is the single most important variable necessary to support research, monitoring and management of alien and invasive species” GBIF.

Standard Biodiversity Definitions

Official Definitions Are Inclusive:

Scientific definitions of biodiversity do not exclude non-native species. As Britannica notes, biodiversity is defined as “the variety of life found in a place on Earth” and biologists most often define it as “the totality of genes, species and ecosystems of a region.” The most common measure is “species richness” – simply “the count of species in an area” BritannicaWikipedia.

The Convention on Biological Diversity (CBD) “emphasises the role of biodiversity in delivering benefits essential for all people and, as a result, seeks to safeguard all life-forms.” Research argues that “the absence of non-native species from biodiversity indices stands in contradiction to the CBD and Sustainable Development Goals {SDGs}” Do non-native species contribute to biodiversity? – PMC.

Scientific Consensus vs. Conservation Advocacy

The Evidence Shows Division:

A 2019 survey of 314 researchers found that “overall, a majority of respondents in our sample supported statements that the species-component of biodiversity should include all species (55%) or some types of non-native species” Diverse views among scientists on non-native species. This indicates significant scientific support for including non-native species in biodiversity measures.

However, there’s strong opposition from some conservation biologists. The IUCN argues it’s “misguided and potentially disastrous to consider native and non-native species as equal from the standpoint of both ecosystem services and conservation goals” Do non-native species count as biodiversity? – Crossroads blog | IUCN.

Practical Measurement Reality

How Biodiversity Is Actually Measured:

Standard biodiversity indices like Shannon diversity, Simpson diversity, and species richness simply count all species present. These indices “do not discriminate between species and communities with very different functionalities” and follow “a leading principle that ‘all species and individuals are considered equal'” 22.2: Diversity Indices – Biology LibreTexts +2.

Research shows that “the introduction of a non-native species increases the local species count (by one!)” and “because of the spread of non-natives, a general trend worldwide is that often local biodiversity (measured by a species count) is increasing even while overall global species numbers are in decline” Understanding and Defending the Preference for Native Species | SpringerLink.

Key Contextual Points

The Complexity of the Issue:

Scientists recognize this is “a broader social debate about what type of nature we need to ensure a good life for present and future generations.” The discussion involves “not only a scientific debate about the contributions of these species to society but also a broader social debate” Do non-native species contribute to biodiversity? – PMC.

Even in conservation contexts, scientists often use the term “alien species” rather than “invasive species” because “‘invasive’ suggests invasion potential and negative ecological effects, which is not necessarily the case for all alien species” Species data for understanding biodiversity dynamics: The what, where and when of species occurrence data collection – Petersen – 2021 – Ecological Solutions and Evidence – Wiley Online Library.

Conclusion

The available data clearly shows that:

Standard scientific practice: Most biodiversity measurements and major databases include all species regardless of origin
Official definitions: Neither CBD nor standard scientific definitions of biodiversity exclude non-native species
Research consensus: A majority of surveyed scientists support including non-native species in biodiversity measures
Conservation advocacy: Some conservation biologists argue for native-only measures, but this appears to be a minority position in the broader scientific community

The claim that “biodiversity only includes native plants” appears to be an ideological position held by some in the invasion biology community rather than the standard scientific practice for measuring biodiversity.