Nativism turns a blind eye to climate change

“Reflexive demonization of alien species ignores the beautiful but complex truth that nature fights to find a way—and for a planet navigating the pressures of climate change and overpopulation, that just might be our saving grace.” – Marianne Willburn, Garden Rant

Margaret Renkl writes an opinion column for the New York Times that I usually enjoy because she frequently writes about nature, often based on observations of wildlife in her own garden.  She lives in her childhood home in Nashville, Tennessee.  Much of her garden was planted with non-native plants and trees decades ago by her deceased mother.  Yet, in a recent column, Ms. Renkl blames non-native plants for a variety of crimes against nature. 

  • She suggests that non-native trees are blooming earlier than native trees, which she says has “skewed our experience of spring.”  She is apparently unaware that spring does indeed arrive earlier than it has in the past because of climate change.  Warmer weather arrives earlier, triggering the blooms of spring, not vice versa.  Both native and non-native plants are blooming earlier than they did in the past. 
  • She suggests that gardens planted with non-native plants are “blooming wastelands where the flowers feed nobody at all,” yet her columns are usually filled with the wildlife that lives in her own garden, with introduced plant species.
  • Although she does not use pesticides in her own garden, she believes that her neighbors’ non-native gardens require them to use pesticides that kill wildlife.  She says, “The typical suburban yard is actually worse than a wasteland. It’s a death trap.” She does not seem to know that most herbicide is used to kill non-native plants, not native plants nor does she seem to realize the contradiction in her indictment of gardening with non-native plants.  If there are more insects living in native gardens than non-native gardens, why would more pesticide be needed in non-native gardens?  If people could learn to love the clover, dandelions, and English daisies in their lawns as much as I do, they would use less “weed killers” on their lawns.

Ms. Renkl’s misperceptions about non-native plants seem to be based on a mistaken belief in their origins.  She says, “Ambulatory and omnivorous, human beings are a migratory species. That’s not true for the vast majority of plants.”  In fact, plants are just as mobile as animals, including humans.  Plants are carried by birds, animals, wind, ocean currents, etc.  They come and go as the climate changes, as it has many times in the past 500 million years that plants have existed on Earth.  Plants now considered non-native existed here in the distant past, in a different climate.  Here are a few examples of such dispersals; most occurred before humans even existed:

The ability to migrate is essential to the survival of plant and animal species.  As the climate changes, this survival strategy is quickly becoming even more important.  When we demand that plants be restricted to their historical “native” ranges, we doom them to extinction because when the climate changes, the vegetation must change.

Where did Ms. Renkl learn these myths?

Ms. Renkl’s cites Doug Tallamy’s Nature’s Best Hope as one of the sources of her mistaken beliefs.  Tallamy considers the existence of non-native plants the root of all evil in nature.  He calls them “ecological tumors.” He blames non-native plants for declining populations of both native plants and insects, and by extension to declining populations of birds that eat insects. 

In Nature’s Best Hope, Tallamy says, “…we must not use climate change as an excuse to do nothing.  Most species of plants and animals are far more resilient to climate variability than we give them credit for.  Besides, increasing the number and biomass of the plantings in our yards and public spaces is one of our most accessible and convenient tools to fight climate change.”  The problem with Tallamy’s dogma is that it inspires the public and land managers to eradicate established landscapes that are not native based on Tallamy’s claims that non-natives are “crowding out” native species and depriving wildlife of food. All native plant “restorations” begin by eradicating non-native plants, usually with herbicides that retard new growth.  In other words, the native plant ideology is causing the loss of vegetation and therefore the loss of stored carbon and the reduced capacity for carbon sequestration in the future.  The native plant ideology is not increasing biodiversity, nor is it “fighting climate change.”  It is more destructive than constructive. 

I’m not looking for “an excuse to do nothing.”  On the contrary, I believe every effort must be made to stop or at least slow down the inexorable advance of climate change.  The most basic effort we can make is to stop destroying functional vegetation, especially trees.  Then, there is a lengthy list of what we should be doing to reduce greenhouse gas emissions, which is another, equally important topic. 

Native plant advocates consider climate change irrelevant because they believe the existence of non-native plants is the sole culprit of all problems in the environment.  They see every environmental issue through the narrow lens of their dogma.  This comment on an article about the value of non-native plants by Marlene Condon published in [Chesapeake] Bay Journal is an example of such a misinterpretation of an environmental issue:

“English ivy is an evergreen, non-native, invasive groundcover that has demolished undisturbed natural areas…In salmon country that’s the difference between clean, cold streams and warmer streams filled with sediment.”

Eradicating ivy on stream banks is likely to produce more sediment because it will take some time for replacement vegetation to cover the ground, especially if herbicides are used to eradicate the ivy. Water is warmer in streams because of climate change and because there is less water due to water diversion and droughts. There are many other reasons for declining populations of salmon, particularly dams that prevent salmon from reaching their spawning grounds upstream.

Treat the cause, not the symptom

The native plant ideology ignores the underlying causes of changing ecosystems. Most changes are caused by the activities of humans, such as agriculture, development, water diversion, and pesticides.  Climate change is the underlying cause of some changes in nature and it will steadily become a more important factor.  Eradicating non-native plants will not reverse any of those changes nor will it prevent changes in the climate.    


  1. Alan de Queiroz, “The resurrection of oceanic dispersal in historical biogeography,” Trends in Ecology and Evolution, 20 No. 2, February 2005

Photo credit for featured photo: Garden Rant, Marianne Willburn

The National Park Service has an epiphany

“We were probably always wrong to think about protected places as static.” – NPS Scientist

During the Trump administration federal agencies were forced to be silent about climate change.  Behind closed doors, many federal agencies were quietly preparing for the day when they would be able to begin the process of adapting to climate change. 

Shortly after the 2020 presidential election, the National Park Service published a natural resources report that announced a radical departure from traditional conservation strategy that was based on an assumption that nature is static and evolution a historical event.  “Resist-Accept-Direct—A framework for the 21st century resource manager” acknowledged that the rapidly changing climate requires a new approach based on the knowledge that nature is dynamic and evolution is a current and continuous event.  Many other federal agencies participated in the preparation of the report, which implies that other federal agencies may adopt the new conservation strategy. (1)

In April 2021, the National Park Service published policy guidance for park managers based on the principles of “Resist-Accept-Direct.” The New York Times interviewed the lead author of the policy guidance, who described the new conservation strategy of the National Park Service:   “The concept of things going back to some historical fixed condition is really just no longer tenable.” 

Acadia National Park, Maine

An ecologist and the science coordinator of Acadia National Park in Maine told NY Times what this new strategy meant to him and his colleagues.  He said that as recently as 2007 protected areas like the national parks were still being thought about as static places that could be preserved forever with the right techniques. “We weren’t being trained on how to manage for change,” he said. “We were being trained on how to keep things like they were in the past.”  That means nearly everyone in his line of work was caught unprepared for the current reality. “You have a whole profession of people having to shift how we think.  We were probably always wrong to think about protected places as static.”

Evolution of National Park Service Policy:  From preservation to restoration

The federal law that established the National Park Service in 1916, defined its mission:

“…which purpose is to conserve the scenery and the natural and historic objects and the wild life therein and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations.”

H.R. 15522, An Act to establish a National Park Service, engrossed August 5, 1916 (1)

Preservation was the original mission of the National Park Service.  In 1963, the mission of the National Park Service was radically changed by the Leopold Report, written by A. Starker Leopold, the son of Aldo Leopold.  The Leopold Report recommended a goal for national parks of maintaining historical conditions as closely as possible to those “of primitive America.”  When the Leopold Report was adopted as official policy by the National Park Service in 1967, it committed NPS to restoring park lands to pre-settlement conditions:

“Passive protection is not enough. Active management of the natural environment, plus a sensitive application of discipline in park planning, use, and development, are requirements for today’ Simultaneously, that edition of NPS policies also described the primary management task as a seemingly simple undertaking: ‘[safeguard] forests, wildlife, and natural features against direct removal, impairment, or destruction,’ and ‘[apply] ecological management techniques to neutralize the unnatural influences of man, thus permitting the natural environment to be maintained essentially by natural agents’” (1)

In 1967, the land management goals of the National Park Service became more ambitious.  The goal of “preservation” was replaced by the goal of “restoring” historic landscapes and ecosystems.  The pre-settlement landscape of 500 years ago on the East Coast and 250 years ago on the West Coast was established as the baseline landscape that NPS was committed to re-creating.  The baseline landscape was presumed to be “pristine” although it had been actively gardened by indigenous people for thousands of years.

The new land management strategy of the National Park Service

The National Park Service calls its new land management strategy the RAD framework, an acronym that summarizes three alternative strategies:  

  1. “Resist the trajectory of change, by working to maintain or restore ecosystem processes, function, structure, or composition based upon historical or acceptable current conditions.
  2. “Accept the trajectory of change, by allowing ecosystem processes, function, structure, or composition to change, without intervening to alter their trajectory.
  3. “Direct the trajectory of change, by actively shaping ecosystem processes, function, structure, or composition towards desired new conditions.” (1)

Every land management decision will choose among these alternatives based on an analysis that will begin with a climate assessment. Instead of looking to the past for guidance, the planning process will assess current conditions and project future climate conditions.  Based on that assessment, the purpose of land management plans will be adaptation to current and anticipated conditions.  Every plan will be designed for a specific place, based on specific current and anticipated conditions.  There is no one-size-fits-all plan, only a framework for devising individual plans tailored for specific parks or ecosystems within parks. 

The new strategy also makes a commitment to monitor the project as plans are implemented and modify the strategy as the environment continues to change and the ecosystem responds to land management.  This is called “adaptive management” and it is essential in a rapidly changing environment. The project doesn’t end, because nature never stops changing.  It’s a process for which there is no end-stage.

It’s a challenging strategy, but one that has the potential to be less destructive than the “restoration” paradigm that always began by destroying plants and animals perceived as intruders without historical precedents.  Precisely what it will mean remains to be seen.  There will probably be pockets of resistance from those who remain committed to the “restoration” paradigm and those who are economically dependent on existing projects.  All the more reason to continue to watch what is being done and participate in whatever public process is available

An example of an NPS project that should be abandoned.

There are undoubtedly hundreds, perhaps thousands of NPS projects that are based on the ambitious restoration goals of the 1963 Leopold Report.  Perhaps some were successful.  My personal knowledge of NPS projects is limited to those in the San Francisco Bay Area, my home.

Point Reyes National Seashore

An attempt to eradicate European beach grass in the Point Reyes National Seashore (PRNS) is an example of an NPS “restoration” project that should be abandoned if the new RAD framework is implemented.  The PRNS project was described by NPS staff at the 2018 conference of the California Invasive Plant Council, a source and a setting that should be considered credible by the most ardent supporters of ecological “restorations.”

About 60% of sand dunes in the Point Reyes National Seashore were covered in European beach grass when the eradication effort began in 2000.  The goal of the project was to restore native dune plants and increase the population of endangered snowy plovers that nest on bare sand.  The project began by manually pulling beach grass from 30 acres of dunes at Abbott’s Lagoon.  The grass grew back within one year, presumably because the roots of the beach grass are about 10 feet long.  Manually pulling the grass from the surface does not destroy the roots. 

A new method was devised that was more successful with respect to eradicating the beach grass.  The grass and its roots were plowed up by bulldozers and buried deep in the sand.  The cost of that method was prohibitively expensive at $25,000 to $30,000 per acre and the barren sand caused other problems.  The barren dunes were mobile in the wind.  Sand blew into adjacent ranches and residential areas, causing neighbors of the park to object to the project.  The sand also encroached into areas where there were native plants, burying them.  The bare sand was eventually colonized by “secondary invaders.”  Different non-native plants replaced the beach grass because they were more competitive than the desired native plants. 

In 2011, the National Park Service adopted a third strategy for converting beach grass to native dune plants.  They sprayed the beach grass with a mixture of glyphosate and imazapyr.  At $2,500 to $3,000 per acre, this eradication method was significantly cheaper than the mechanical method.  However, it resulted in different problems that prevented the establishment of native dune plants.  The poisoned thatch of dead beach grass was a physical barrier to successful seed germination and establishment of a new landscape.  Where secondary invaders were capable of penetrating the dead thatch, the resulting vegetation does not resemble native dunes. 

Presentation at California Invasive Plant Council conference regarding attempt to eradicate European beach grass at Point Reyes National Seashore, November 2018

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

Presentation at California Invasive Plant Council conference regarding attempt to eradicate European beach grass at Point Reyes National Seashore. November 2018

Looking forward, not back

The realization—or perhaps acknowledgement—that the NPS strategy of re-creating historical landscapes is unrealistic was a long time coming.  Over the 50 years that the “restoration” strategy was attempted much unnecessary damage was done.  Useful, functional landscapes were destroyed.  Healthy trees were destroyed solely because they were planted by Europeans.  Animals were killed because they were perceived to be competitors of “native” animals.  Herbicides poisoned the soil, preventing regeneration or germination of new vegetation.  Established landscapes that had not needed irrigation were replaced with native plants that required irrigation.  Stabilizing vegetation was destroyed, resulting in erosion and drifting sand. 

The National Park Service has awakened to the failure of their “restoration” strategy because of the combination of failed projects that were based on mistaken assumptions and the impacts of climate change. NPS led public land managers into the dead end of attempting to re-create historical landscapes. Now NPS will lead public land managers out of that dead end into the reality of a changed environment with a rapidly changing future. Better late than never.


  1. Schuurman, G. W., C. Hawkins Hoffman, D. N. Cole, D. J. Lawrence, J. M. Morton, D. R. Magness, A. E. Cravens, S. Covington, R. O’Malley, and N. A. Fisichelli. 2020. Resist-accept-direct (RAD)—a framework for the 21st-century natural resource manager. Natural Resource Report NPS/NRSS/CCRP/NRR—2020/ 2213. National Park Service, Fort Collins, Colorado. https://doi.org/10.36967/nrr-2283597
  2. Planning for a Changing Climate: Climate-Smart Planning and Management in the National Park Service, NPS, April 2021.  https://toolkit.climate.gov/reports/planning-changing-climate-climate-smart-planning-and-management-national-park-service

Featured Photo from RAD Natural Resource Report.  Photo caption:

“Multiple federal agencies, including the National Park Service (Bandelier National Monument), tribes, and others steward the East Jemez Mountains ecosystem of New Mexico, an ecologically transforming landscape where massive forest die-off is projected to occur more frequently in the future. Piñon pines, normally evergreen, have reddish-brown foliage in October 2002 (left). By May 2004 (right), the dead piñon pines lost all their needles, exposing gray trunks and branches. The photos were taken from the same vantage point near Los Alamos, N.M. Forest drought stress is strongly correlated with tree mortality from poor growth, bark beetle outbreaks, and high-severity fire. Credit: C. Allen, USGS” (1)

The Grand Delusion: Controlling Nature

“This is a book about people trying to solve problems created by people trying to solve problems.”

Elizabeth Kolbert’s earlier book, The Sixth Extinction was ground-breaking, not because it described the consequences of climate change in the 21st Century, but because it put modern climate change into the context of similar events in the past 500 million years of life on Earth.  Although the current episode of climate change is man-made, five previous mass extinctions were natural events.  What past extinction events have in common with the sixth extinction is the inevitable consequence of such changes in climate:  when the climate changes, all life on Earth changes with it.  Plants and animals will adapt, change, or they will go extinct as they have for 500 million years. (1)

Kolbert’s new book, Under a White Sky, turns the page on this cataclysmic event in the Earth’s history to focus on the efforts being made to control nature to address environmental problems, including climate change.  To say that Kolbert is skeptical of those efforts is to understate her critical evaluation of them. 

Controlling Nature

In 1990, I was introduced to the human delusion that we can control nature by John McPhee’s The Control of Nature.  His book had a profound influence on my thinking about nature.  It was the basis for my belief that attempts to turn back the botanical clock to 500 years ago to a pre-settlement landscape, mistakenly believed to be pristine, are futile, misguided, and often damaging.  Kolbert’s latest book is written from the same perspective as McPhee’s seminal work and she gives him credit for his pioneering work.

Map of Mississippi River Delta

McPhee’s book predicted the catastrophic flooding of New Orleans by hurricane Katrina in 2005.  Human engineering of the Mississippi River for over 100 years set the stage for that disaster.  New Orleans sits at the Gulf end of the Mississippi River.  Historically, the river flowed from Minnesota to the Gulf, accumulating sediment along its way and depositing it as it entered the Gulf, fanning out into streams and swamps that created the Mississippi Delta.  The labyrinth of land and marsh created by the sediment deposited by the river created a barrier that protected New Orleans from storms. 

However, the uncontrolled and episodic flow of the river caused periodic flooding that was not convenient for the human inhabitants of New Orleans and the Delta community.  So, the flow of the river was controlled by levees and pumps were used to return water from the land to the river.  Sediment from the river could no longer replenish the land because it was confined to the constrained river, which put the human engineers onto a never-ending treadmill of building higher levees and bigger pumps.  It was inevitable that the river would eventually overwhelm the defenses built by the engineers and so it did during Katrina in 2005.

Kolbert updates this untenable situation in the Mississippi Delta in her new book.  The underlying cause, as told by McPhee is recapped by Kolbert.  Then new manmade environmental issues are added to the catastrophic circumstances that will inevitably doom the human inhabitants.  Rising sea levels caused by climate change are one factor.  The incursion of salt water into fresh water swamps killed vegetation that acts as a buffer during storms. Oil and gas exploration and extraction in the Delta has caused the land to drop further. 

Many Delta communities and some neighborhoods in New Orleans have been abandoned because they are essentially underwater.  Since Katrina, no serious effort has been made to change the approach to the issues.  Bigger, more powerful pumps have been built and levees have been made higher and stronger.  No one is seriously considering the need to relocate New Orleans or surrounding communities to higher ground.  The delusion that humans can outsmart the river continues. 

A comedy of errors

Kolbert introduces the many projects that are trying to solve problems that were created by bad decisions made earlier by other humans with a quote from Albert Einstein: “We cannot solve our problems with the same thinking we used when we created them.”  These wise words from a wise man are clearly not being heeded by the masterminds of the projects Kolbert describes in her book:

Dead carp
  • High on the list of projects in which society is heavily investing is the attempt to prevent carp from entering the Great Lakes from the Mississippi River.  After many different approaches were tried and failed, the current strategy is an electrified fence separating the Chicago River (connecting to the Mississippi River) from Lake Michigan that kills untold thousands of fish every day.  This deadly project is the end stage of previous bad decisions.  A link between Lake Michigan and the Mississippi River was created by a massive engineering project that reversed the flow of the Chicago River in 1887.  Later, carp was introduced to the Mississippi River from China as biological control to address pollution issues.  One species of carp was introduced to control aquatic weeds and another carp species was introduced to consume nutrients in sewage ponds.  Kolbert says such biological controls became popular after Silent Spring was published because Rachel Carson considered pesticides a curse and biological control a panacea. (Which is not to say that pesticides aren’t a curse.) In other words, we traded one problem for another.
  • Island eradications of introduced mammals such as rats and mice are also popular projects (with some people).  Genetic engineering is being aggressively pursued as a possible substitute for the rodenticides that are being used for these projects.  These projects have the potential to drive an entire species into extinction or alter their physiology such that they could become killers or prevent them from being killers.  Kolbert buys a genetic engineering kit for $209 from a young entrepreneur in Oakland that enables her to make E.coli cells resistant to an antibiotic.  E.coli is a deadly bacteria that can be fatal if untreated by antibiotics.  In other words, anyone with $209 can turn bacteria into killers with no special training or equipment.  What could possibly go wrong, Kolbert asks rhetorically.

The promise and threat of geoengineering

Kolbert visits several different geoengineering projects that are trying to prevent the consequences of climate change without reducing greenhouse gas emissions, the underlying cause of climate change.  One such project is turning CO₂ into stone.  Apparently it CAN be done, but to do it on a scale that would actually prevent climate change would be to devote much of the surface of the Earth to that purpose. 

Kolbert visits a project that believes injecting aerosols into the atmosphere to block the sun is the best bet to stop climate change.  The proposal strikes Kolbert as both preposterous and dangerous.  The researcher detects her skepticism and retorts, “People think of all the bad examples of environmental modification.  They forget all the ones that are more or less working.  There’s a weed, tamarisk, originally from Egypt.  It’s spread all around the desert Southwest and has been destructive.  After a bunch of trials, they imported some bug that eats the tamarisk, and apparently it’s kind of working.” 

Tamarisk defoliation along Colorado River, near Needles, California

In fact, the introduced tamarisk beetle is working too well.  It has spread far beyond the regions where it was introduced and produced wastelands of dead trees in Arizona and Southern California.  Since one of the rarest desert birds depends upon tamarisk there isn’t much to celebrate about this over-achiever beetle.

Compounding the problem

Instead of addressing the source of environmental issues, we compound them by creating new problems with our theoretical “fixes.”  The native plant movement, in their zeal to save native plants, sprays herbicides that kill as many native plants as non-native plants and poison the soil while doing so, stunting all new growth, both native and non-native. 

I share Kolbert’s skepticism about the projects she describes for the same reasons she gives.  Every “fix” has the potential to create new problems that could be more disastrous than the problems they are meant to resolve.  And the resources used to develop new techniques such as massive geoengineering projects could be used instead to address the underlying cause of the problem, which is the greenhouse gas emissions causing climate change.  We don’t want to give up our fossil-fuel driven economy, so instead we conjure up even more damaging ways to ameliorate the inconveniences of climate change.  It’s a fantasy that prolongs and exacerbates the consequences of climate change.

Finally, let’s give Kolbert the last word:  “This has been a book about people trying to solve problems created by people trying to solve problems…Geoengineering may be ‘entirely crazy and quite disconcerting,’ but if it could slow the melting of the Greenland ice sheet, or take some of ‘the pain and suffering away,’ or help prevent no-longer-fully-natural ecosystems from collapsing, doesn’t it have to be considered?…But to imagine that ‘dimming the fucking sun’ could be less dangerous than not dimming it, you have to imagine not only that the technology will work according to plan but it will be deployed according to plan.  And that’s a lot of imagining…But let’s just say the record here isn’t strong.”  (2)

Thank you, Elizabeth Kolbert, for calling out the grand delusions of humans who mistakenly believe it is possible to control nature to avoid inconveniencing human society. 


  1. Elizabeth Kolbert, The Sixth Extinction, Henry Holt and Co., 2014
  2. Elizabeth Kolbert, Under a White Sky, Crown New York, 2021

What does this mean: “Nature-based solutions to achieve California’s climate change and biodiversity goals”?

In October 2020, Governor Newsom signed Executive Order N-82-20 “enlisting California’s vast network of natural and working lands – forests, rangelands, farms, wetlands, coast, deserts and urban greenspaces – in the fight against climate change. A core pillar of Governor Newsom’s climate agenda, these novel approaches will help clean the air and water for communities throughout the state and support California’s unique biodiversity.”

The California Natural Resources Agency has invited the public to tell them what you think that means.  They are holding a series of virtual on-line workshops (register here) and they are inviting the public to complete a survey (available here) by the deadline of May 14, 2021.  Recordings of workshops that have already taken place are available HERE.   Email address for feedback and questions is californianature@resources.ca.gov.

Click on picture to see San Francisco Bay Area regional workshop

I attended one of the workshops and I’ve read the material available on their website.  This is what little I can tell you about the project.  There seem to be three elements to this initiative:

  • The Natural and Working Lands Climate Smart Strategy will “expand climate smart land management across California to achieving carbon neutrality and reduce climate risks to communities and ecosystems and build climate resilience across California.”
  • The 30X30 initiative establishes a state goal of conserving at least 30 percent of California’s land and coastal waters by 2030, while “safeguarding our State’s economic sustainability and food security, protecting and restoring biodiversity.” Conservation measures will focus on a “broad range of landscapes, including natural areas and working lands, in partnership with land managers and natural resource user groups while building climate resilience and reducing risk from extreme climate events.”  Projects will also “expand equitable outdoor access and recreation for all Californians.”  Approximately 22% of land in California is presently protected, but only 16% of our coastal waters. 
  • “The California Biodiversity Collaborative will bring together groups and leaders from across our state to take bold action to maintain California’s extraordinary natural richness. This Collaborative was a directive set forth in Governor Newsom’s 30×30 Executive Order and is the next generation of the State’s Biodiversity Initiative.”

I have no idea what these vague commitments mean when they are translated into specific land acquisitions and funded projects, but I know that non-governmental organizations see this as an opportunity to obtain funding for what they want. 

Only 10% of the audience for the San Francisco Bay Region workshop was the general public. Over 50% of the 280 people at the workshop (by far the largest constituency at the workshop) I attended were employees of non-governmental organizations.  The California Invasive Plant Council (Cal-IPC) asked their members to attend the workshops and participate in them:  “This is a critical opportunity to make sure the need for invasive plant management is heard, loud and clear. We encourage you to attend to learn more about 30×30 and share your ideas.”  These are Cal-IPC’s suggestions for participants:  “Several points to consider making: (1) the definition of “protected” — and the metrics used to measure 30×30 success — need to include adequate funding for ongoing stewardship; (2) funding for the Weed Management Area (WMA) program is critical for county collaborations staying on top of high priority invasive plants across jurisdictional boundaries; (3) wildfire fuels reduction should follow best practices, including control of invasive plants, so that habitat is enhanced, not damaged.” California Native Plant Society is also asking its membership to participate in the 30 X 30 public outreach effort in support of CNPS objectives.

If you have your own priorities for how your tax dollars are used, you may want to participate in this public process as well because the projects will have an impact on land management practices throughout the State of California.  Please consider attending a workshop and completing the long, complex, and vague on-line survey by May 14, 2021.  I have no idea if the California Natural Resources Agency will take the public’s input into consideration, but I know this:  If you don’t participate, you will take whatever you get. 

What I WANT it to mean

This initiative is going to be a major public investment and non-governmental non-profit organizations see it as an opportunity to fund their projects.  The disparate goals of this initiative are often in conflict.  If climate change solutions and related wildfire hazard reduction goals conflict with biodiversity goals, addressing climate change hazards must be the top priority because all life is threatened by the consequences of climate change.  The public must understand that when the climate changes, the vegetation changes.  The ranges of native plants and animals have changed and will continue to change in response to climate change.  Native vegetation is not inherently less flammable than non-native vegetation.

On August 18, 2020, the CZU Lightning Complex Fire swept through Big Basin Redwoods State Park, burning over 97% of the land, forested in native redwood trees. (AP Photo/NicCoury published by CA State Parks)

The native plant movement is a form of climate change denial.  We cannot replicate the landscape of 250 years ago, as native plant advocates wish, because it is not adapted to the current and anticipated climate.  Biodiversity is appropriately defined as all species of plants and animals, regardless of their origins.  Forests are major carbon sinks, whether they are native or considered non-native by people with a short-term perspective of nature and evolution.

Over 160 million native conifers have died in California in the past 8 years. They were killed by high temperatures, drought, and native bark beetles. All of these factors are consequences of climate change.

The survey for this project is not user friendly.  Within its constraints, here is a sample of the specific points I was able to make:  “Do not fund projects that use pesticides, including herbicides.  Do not replace established vegetation that does not require irrigation with vegetation that will require irrigation to become established.  Do not fund projects that will require recreational access restrictions. Stop eradicating non-native spartina marsh grass with herbicides because it protects wetlands year around from storm surges.  Where afforestation is possible, plant only trees that are adapted to the current and anticipated climate. Fund projects that protect residential communities from coastal flooding and salt-water incursion into ground water. Fuels management projects must assume that native and non-native vegetation is equally flammable because flammability is unrelated to the origin of plants.  If climate solutions conflict with biodiversity goals, climate solutions should be the top priority because all life is threatened by climate change.  If fuels management goals conflict with biodiversity goals, fire safety should be the top priority.”

Computer models predict the future? Garbage in, garbage out

Computer modeling is an increasingly popular tool used in ecological studies.  The rapidly changing climate is putting pressure on scientists to predict the trajectory of the change and the impacts those changes will have on the environment.  However, a computer model is only as predictive as the assumptions used to build it.  In other words, “garbage in, garbage out.”

That sets the stage for a study published in 2018 that predicted that “grassland may be a more reliable carbon sink than forests in California.”(1) The study was quickly adopted by native plant advocates as a weapon in their battle to destroy non-native trees in favor of grassland they prefer. (2) They prefer grassland because it was the pre-settlement coastal landscape.  They don’t acknowledge that burning by Native Americans and grazing by native ungulates were the primary reasons why grassland did not succeed to shrubs and forests prior to settlement. Pre-settlement grassland was as much a human creation as any modern landscape.

Source: US EPA, 2018

Most carbon storage is below ground, in roots and soil.  That is true of both grassland and forests. If the forest burns, the carbon it has stored in soil remains, just as the below ground carbon sink of grassland remains. 

The study (1) that claims grassland may be a more reliable carbon sink than forests reaches its erroneous conclusion by comparing below ground carbon storage in grassland with above ground carbon storage in forests. It’s a classic case of inappropriately comparing apples with oranges to the disadvantage of forests.  It seemed such an unlikely comparison that I asked the study’s authors to confirm they had compared below ground carbon storage in grassland with above ground carbon storage in forests.  They confirmed that they did, indeed, make that inappropriate comparison.

The study also bolsters its mistaken conclusions by erroneously claiming that forests are more likely to burn than grasses:

“The fire resistance for grasses is 0.5 while that of trees range from 0.1−0.3, making grasses more resistant to wildfires than trees, which is roughly consistent with field-observations since in the event of a wildfire, when compared to trees, a smaller fraction of the biomass of grass is damaged.” (1)

However, the study cited as the source of this statement (3) says exactly the opposite:

“The fraction of individuals killed depends upon the prescribed PFT fire resistance, which represents the PFT survivorship during a fire (see Table 1). In the fire model, grasses and litter are fully consumed.” (3)

Table 1 PFT parameter values for fire resistance
PFTFire Resistance (%)
Woody
Tropical broad-leaved evergreen12.0
Tropical broad-leaved raingreen50.0
Temperate needle-leaved evergreen12.0
Temperate broad-leaved evergreen50.0
Temperate broad-leaved summergreen12.0
Boreal needle-leaved evergreen12.0
Boreal summergreen12.0
Grasses
C3 grass100.0
C4 grass100.0

Table 1 is consistent with this statement in the abstract of the cited study:  “Estimated litter moisture is the main driver of day‐to‐day fire probability.”  (3) Forests retain more moisture in the soil and leaf litter because of the shade provided by the tree canopy.  I wrote to the study author again, asking “where is the source of your statement that grasses are more fire resistant than trees?”  He did not reply.

If a study doesn’t seem to make sense, or it contradicts other sources of information, it is worthwhile to look under the hood.  What is driving the model?  Is it fueled by hot air?  Is it serving an activist agenda? Are cited studies accurately quoted? 

Some truth emerges from the model’s black box

Despite the erroneous assumptions of the computer model used by this study, there is some truth in the conclusions it reaches.  Vegetation type conversions are occurring now and they will continue as the climate continues to change because when the climate changes, the vegetation changes. We are presently witnessing the transition of native conifers at high altitudes to lower altitude hardwood trees. Although these changes will occur gradually and there will be many intermediary transitions, the fact is that grassland is more likely to survive than forests in a warmer, drier climate in the long run. 

The Guardian has published a comprehensive report about the loss of forests all over the world.  In the Rocky Mountains, one-third of places where trees burned 20 years ago are now occupied by shrubs and flowers.  About 15% of forests in the Rocky Mountains are not expected to grow back if killed by fire because the climate is no longer suitable for them.  About half of existing forests in Alberta, Canada are expected to vanish by 2100.  The “megadrought” in south-western US is expected to convert 30% of forests to shrubland or another type of ecosystem.

In the short run, the loss of forests can be mitigated by reforestation with tree species that are better adapted to a warmer, drier climate.  The study (1) acknowledges the potential for mitigation to preserve forest ecosystems:  Factors such as species traits, biodiversity, rapid evolution, and human management intervention could alter our model-based findings from the projections provided here. Consequently, our results indicate the potential direction of change as opposed to predictions that consider the full ensemble of ecological, physiological and management factors that can alter pathways and responses of ecosystems to climate change.”

From the standpoint of carbon storage, it is not good news that grassland is likely to inherit hot, dry lands previously occupied by forests.  Forests and wetlands store more carbon than grasslands, as the above chart in a USDA publication about carbon storage shows.  Sustaining below ground carbon sinks will depend on carbon sequestration by above-ground plants and trees.  Because above-ground carbon sequestration is primarily dependent upon the biomass, forests will always do a better job than grassland in the long run.  In the short-run, grassland will grow back more quickly than forests, but it will never achieve comparable biomass. 

Forests are presently absorbing about one-quarter of all human carbon emissions annually. Forests make a significant contribution to reducing carbon emissions, but planting trees is not a panacea as long we continue to burn fossil fuels to generate energy. The loss of carbon-sequestering capabilities of forests will exacerbate climate change in the long-run.  It’s one of many dreaded feedback loops that are reaching tipping points:  the impacts of climate change are destroying the mechanisms that mitigate climate change. 

The study (1) acknowledges that by the end of the 21st Century, under current climate conditions (warming limited to 0.3⁰ – 1.7⁰ Centigrade) forests will have removed 5 times more net carbon (carbon storage minus carbon loss) per hectare from the atmosphere than grassland in California.  See Table 1 in the study (1).  Thus, the study agrees that forests store more carbon than grassland.

From the standpoint of wildlife, it is not good news that grassland is likely to replace forests in a warmer climate. The insects, birds, and animals that live in the forest will lose their habitat. Forests are home to over 80% of terrestrial species.  We will lose our shade in a warming climate and our windbreak. 

Not an argument for destroying forests

This study (1) is unfortunately being used by the native plant movement to advocate for the preemptive destruction of healthy urban forests that are not more likely than native forests to burn in wildfires.  Virtually all wildfires in California occur in native vegetation. There is no advantage to destroying healthy forests that are expected to live for another 100-200 years.  We don’t amputate our limbs to avoid breaking them.  Nor should we destroy our forests before they die.

(1)“Grasslands may be more reliable carbon sinks than forests in California,” Pawlok Dass, Benjamin Z Houlton, Yingping Wang and David Warlind, 10 July 2018, Environmental Research Letters, Volume 13, Number 7 

(2) “Importance of Grasslands for Carbon Storage,” Yerba Buena Chapter of California Native Plant Council, Quarterly Newsletter, March 2021, page 6. 

(3) “The role of fire disturbance for global vegetation dynamics: coupling fire into a dynamic global vegetation model,” Thonicke K, Venevsky S, Sitch S and Cramer W 2001,  Glob. Ecol. Biogeogr.10 661–77

Migration: Life on the move

Sonia Shah’s recently published book, The Next Great Migration: The Beauty and Terror of Life on the Move, takes a deep dive into the past to trace the ancient history of migrating life on Earth. For as long as life has existed on Earth, life has been on the move, as needed to survive the constantly changing environment in which all plants and animals live.

1 Homo sapiens
2 Neanderthals
3 Homo erectus

Shah’s is an ambitious attempt to tell this story, not confined to human migration, but encompassing plants and animals as well because all of these migrations are connected. Scientists speculate the earliest migrations of human ancestors, some 100,000 years ago out of Africa, were in pursuit of the migrating animals that humans hunted.  On balance, the movements of plants and animals are beneficial to life on Earth because they are necessary to survive. When they aren’t beneficial, the problems are usually short-lived and humans are usually unable to stop them because nature is more powerful than we are.

Click on map for animated movement of animals in response to changing climate conditions.

Migrations are even more frequent at a time of rapid and extreme climate change. As crops fail in the withering heat and drought caused by global warming, farmers are abandoning their farms to find the food they need to survive. Hence, Shah’s prediction that we are about to witness the “next great migration” because of the challenges of climate change. When the climate changes, the vegetation changes. When the vegetation changes, animals must move to find the food they need. Humans wish to put ourselves in a special category that denies our kinship with animals. But we are as dependent upon our food as any animal and the changing climate will challenge our existence as much as other forms of life.

Shah also traces the brief history of human knowledge of migrations about which little was known before the development of the scientific tools to study it.  Paleontology could dig up fossils that would raise more questions than answers about the residents of deep time, but it wasn’t until the development of molecular analysis that fossils could inform scientists of the evolutionary history of and close relationships among plants and animals that reflect migrations in the distant past.  New technology is capable of tracing the movements of animals that were unknown in the distant past, when animals seemed to mysteriously disappear at the end of one season and returned at the beginning of another season.

Invasion Biology is based on ignorance of migration

The fact that animal migration was largely unknown led to some fundamental misunderstandings about nature, including the unfortunate rise of nativism in the natural world that was spawned by the mistaken hypotheses of invasion biology. Shah explained the consequences of inadequate knowledge of migration in a recently published article in New York Times Magazine:

“When scientists considered movements across barriers and borders, they characterized them as disruptive and outside the norm, even in the absence of direct evidence of either the movements themselves or the negative consequences they purportedly triggered…Influential subdisciplines of biological inquiry focused on the negative impact of long-distance translocations of wild species, presuming that the most significant of these occurred not through the agency of animals on the move but when human trade and travel inadvertently deposited creatures into novel places.  The result, experts in invasion biology and restoration biology said, could be so catastrophic for already-resident species that the interlopers should be repelled or, if already present, eradicated, even before they could cause any detectable damage.”

In turn, Invasion Biology spawned pointless and destructive eradication projects

Conservation Sense and Nonsense has followed the destructive and futile attempts to eradicate plants and animals that nativists say “don’t belong here:”

  • Hawaii is an extreme case of attempts to eradicate non-native plants and animals: frogs, owls, egrets, seals, fruit trees, mangroves, parrots, etc.  These eradication projects often do more harm than good.  The “logic” for these projects is muddled, partly because the Hawaiian Islands emerged from the sea as barren volcanoes.  The question of “what belongs there” is a matter of opinion and debate in Hawaii and elsewhere.

Bird migration routes

Migration enables survival

I hope that improved knowledge of migration will help people understand that migration is a natural phenomenon that is essential to the survival of all life on Earth.  Migration enables life to adapt to changes in the environment, facilitating evolution and reducing frequency of extinction.

Doug Tallamy’s Blame Game

The fact that insect populations are declining in many places around the world is well known, but the reasons for the decline are not well known.  Where there is uncertainty, there is speculation and where there is speculation, there is debate.

Doug Tallamy recently stepped into that debate by publishing a review article about insects and their use of plants.  The article is a mind-numbing list of studies that find both positive and negative relationships between insects and non-native plants.

Tallamy contends those studies add up to support for his belief that non-native plants are bad for insects and native plants are good for insects.  He suggests that declining populations of native plants should be considered one of the reasons for declining populations of insects, but then he goes one step further. Tallamy suggests that non-native plants are responsible for declining populations of native plants.  It follows that Tallamy blames non-native plants for the disappearance of insects.

My interpretation of the studies in Tallamy’s review is different.  The studies tell me that there is too much variation in insect-plant relationships to generalize about the relative value of native vs. non-native plants to insects.  A more accurate conclusion would be that sometimes insects make a successful transition from a native to a non-native plant—especially in the absence of a native in the same lineage—and sometimes they don’t…or at least they haven’t yet.

Anise swallowtail butterfly is one of many insects that have made a successful transition from a disappearing native plant to an introduced non-native plant in the same lineage. Prior to that transition, swallowtails were able to lay eggs only once a year, when the native was available. The introduced non-native is available year around, which enables the swallowtail to lay its eggs year around. Courtesy urbanwildlife.org

Since evolution is a process and not a historical event, these insect/plant relationships will continue to change.  There are many studies that document such transitions and Tallamy cites some of them in his review.  Tallamy assumes insects will be forever handicapped, if not killed, by whatever deficiencies there are in the non-native substitute.  I assume the insect is more likely to adapt and eventually evolve to cope with those deficiencies.  Both our assumptions are just guesses.  Tallamy considers nature immutable, while I consider it dynamic.  Where Tallamy sees doom and gloom, I see opportunity.

Professor Art Shapiro’s (Distinguished Professor of Evolution and Ecology, UC Davis) assessment of Tallamy’s review article is less equivocal than mine.  Keep in mind when reading his assessment that he is far more knowledgeable than I am:

  1. “There is little evidence known to me of alien plants (‘invasives’) competitively displacing natives in ‘communities’ except in highly disturbed environments, except in the case of ‘ecological engineer’ species like Japanese honeysuckle, Himalayan Blackberry, climbing fern in Florida, Purple Loosestrife, etc. — things that drastically alter the ground rules for structuring the vegetation by smothering or prompting fire.

  2. “The use of natives and non-natives by insects has a long and venerable history, going back to T.R.E. Southwood and his comparisons of insect faunas on British trees to Godwin’s history of the British flora, Azevedo’s student study at SF State, etc. — demonstrating overall that enemies accumulate in time on naturalized aliens, but it may be a very slow process if there is no phylogenetic or chemical bridge to their colonization. Experiments using haphazardly-selected species to examine acceptability are basically silly, and very easy to ‘stack’ if one knows one’s phytochemistry.

  3. “As I have repeatedly pointed out, ‘weed’ eradication would lead rapidly to the extirpation of nearly all of the non-tree-feeding urban and suburban butterfly fauna in lowland California (and many other places).”

Why are insect populations declining?

A 2017 study revealed a shocking 76 percent decline in the biomass of flying insects over 27 years in protected areas in Germany.  The German study does not offer specific explanations for the significant decline in insects, but it speculates about probable cause: Agricultural intensification (e.g. pesticide usage, year-round tillage, increased use of fertilizers and frequency of agronomic measures) that we could not incorporate in our analyses, may form a plausible cause. The reserves in which the traps were placed are of limited size in this typical fragmented West-European landscape, and almost all locations (94%) are enclosed by agricultural fields. Part of the explanation could therefore be that the protected areas (serving as insect sources) are affected and drained by the agricultural fields in the broader surroundings (serving as sinks or even as ecological traps). Increased agricultural intensification may have aggravated this reduction in insect abundance in the protected areas over the last few decades.”  Presumably “protected areas” in Germany are not landscaped with non-native plants, rendering the use of this study to corroborate Tallamy’s hypothesis irrelevant.

A comprehensive review of 73 reports of declining insect populations around the globe was published in 2019. These studies report the reasons for declining populations: “The main drivers of species declines appear to be in order of importance: i) habitat loss and conversion to intensive agriculture and urbanization; ii) pollution, mainly that by synthetic pesticides and fertilisers; iii) biological factors, including pathogens and introduced species; and iv) climate change. The latter factor is particularly important in tropical regions, but only affects a minority of species in colder climes and mountain settings of temperate zones.” The “introduced species” are usually insects rather than plants.

In a Yale e360 article about Tallamy’s review, one commenter offers his opinion that the over-population of deer and their preference for eating native vegetation is likely a greater threat to native plants than the existence of non-native plants that provide an alternative source of food for deer, thereby reducing predation of native plants.  Tallamy seems to agree that deer are a problem for native plants, while rejecting deer as a greater threat to native plants than the existence of non-native plants.

The list of reasons for declining insect populations is long and will probably get longer as more research is done.  If the existence of non-native plants is on that list, it is unlikely to be higher on a prioritized list than the pesticides that are being used to eradicate non-native plants.  The more herbicide that is used to eradicate non-native plants, the more harm is done to insects.

EPA Biological Evaluation of glyphosate is a black eye for native plant “restorations” that use herbicide

The Environmental Protection Agency has finally published its Biological Evaluation (BE) of the impact of glyphosate products (all registered formulations of glyphosate products were studied) on endangered animals (mammals, birds, amphibians, reptiles, fish, invertebrates) and plants. The BE reports that 1,676 endangered species are “likely adversely affected” by glyphosate products. That is 93% of the total of 1,795 endangered species evaluated by the study. Of the total of 792 critical habitats of endangered species, 759 (96%) were “likely adversely affected” by glyphosate products.  Most of those critical habitats probably contain predominantly native plants that are clearly not benefiting from herbicides used to kill their competitors.

Both agricultural and non-agricultural uses of glyphosate products were evaluated by the BE. Although only endangered plants and animals were evaluated by the BE, we should assume that all other plants and animals are likewise harmed by glyphosate because the botanical and physiological functions of plants and animals are the same, whether or not they are endangered. Herbicides, specifically glyphosate products, are used by the majority of projects that attempt to eradicate non-native plants. As a result, the crusade against non-native plants is undoubtedly a far more important factor in the decline of insect populations than their mere existence.

Why are native plant populations declining?

There are many reasons why native plant populations are declining, but there is little evidence that non-native plants are the cause of declining populations of native plants. Many of the causes of declining insect populations are also causes of declining populations of native plants. A recent study reports that 65 taxa of native plants in the US and Canada are thought to be extinct. The study did not report a single case in which the extinction was caused by the existence of non-native plants. Sixty-four percent of extinct plants were single-site endemics. The same drivers cited by recent insect studies appear on the list of causes of plant extinctions. Nearly half of the extinctions occurred more than 100 years ago, long before introduced plants were considered an issue.

Butterfly bush is a host plant of Variable checkerspot butterflies. It is also an important source of nectar for butterflies and bees. It is being eradicated on public land because it is not a native plant. butterflybush.com

My New Year’s Wish

Nature is too complex to be reduced to a single cause for changes in the environment.  Human knowledge is insufficient to identify all of the causes.  That’s why we make many mistakes when trying to fix a perceived problem in nature.  Our own priorities influence our evaluation of changes in the environment.  We should not automatically assume that a change is a problem or that it must be reversed.

The existence of novel ecosystems is a case in point.  They can as easily be seen as positive as negative.  If a native plant or animal is no longer adapted to changes in the environment, such as climate change, we should be grateful that a non-native substitute is capable of tolerating the change.  Where some see enemies, others see friends.

I wish you all a very happy New Year in 2021.  I can’t wish 2020 a fond farewell.  I can only say good riddance!  I am hopeful for a more peaceful year, one in which we befriend our enemies and work together for a better world for nature and for humanity.  I am grateful for your readership.

Doug Tallamy’s Nature’s Best Hope denies the value of hybridization

In Nature’s Best Hope, Doug Tallamy concedes that there is no evidence of extinctions of native plants being caused by the introduction of non-native plants in the Continental US.  However, he accuses non-native plants of something more nefarious:  “There is one biological phenomenon associated with some plant invasions that is so pernicious, even continental scales are not protecting natives from invasive species.  I speak of…introgressive hybridization, where the invasive species hybridizes with a closely related native, and then through repeated backcrosses and directional gene flow, the gene pool moves closer and closer to that of the invader.” 

Jake Sigg calls this phenomenon, genetic pollution.  Both Tallamy and Sigg consider such hybridization a loss of the native species and, indeed, it can be the end of localized variants of a species.  However, hybridization is often instrumental in the creation of a new species, one that is often superior to its ancestors because it is better adapted to present environmental conditions.

In a recently published study of the evolution of oaks, scientists traced the 56 million year evolutionary history of roughly 435 species of oak across 5 continents where they are found today.  Oaks are wind-pollinated, leaving pollen fossil records of their presence where they may no longer live.  Using DNA analysis of fossil pollen, scientists tell us when and where oaks have lived.  Their presence or absence was determined by changes in climate that created or eliminated land bridges between continents enabling movement of plants and animals, as well as providing the climate conditions in which oaks can survive.

Hybridization was instrumental in the formation of oak species and the ability of oaks to survive in different climate conditions.  The article in Scientific American about the genetic study of oak species concludes:  “A firm grasp of when, where and how oaks came to be so diverse is crucial to understanding how oaks will resist and adapt to rapidly changing environments. Oaks migrated rapidly as continental glaciers receded starting around 20,000 years ago, and hybridization between species appears to have been key to their rapid response. The insights we can gain from elucidating the adaptive benefits of gene flow are critical to predicting how resilient oaks may be as climate change exposes them to fungal and insect diseases with which they did not evolve.”  

In fact, a recent study suggests that assisted species migration and intentional hybridization are necessary to prevent the extinction of plants in Arctic regions, where the climate is warming the fastest.  Intentionally planting species from warmer regions into colder regions in anticipation of climate warming is called assisted migration.  It is not a new concept.  The study acknowledges that intentional hybridization is a radical suggestion that contradicts conventional wisdom:  “Traditionally, hybridization is viewed as negative and leading to a loss of biodiversity, even though hybridization has increased biodiversity over geological times.  This study acknowledges the role that hybridization plays in increasing biodiversity.

In the Bay Area, we are surrounded by examples of hybridization, some intentional and tolerated and some natural, but not tolerated:

Sycamore. Selectree.

  • Sycamores are the most common street tree in the United States and we have many here in the Bay Area. They are a hybrid of London Plane Trees and our native Sycamore.  The California native was intentionally bred with the London Plane Tree to increase its drought tolerance.   Sycamore street trees are one of the most popular because they are extremely hardy and tolerant of challenging conditions in urban settings.  They are also the host trees of one of our native butterflies, Western Tiger Swallowtail.  The Tiger Swallowtail probably used our native Sycamore in the past, but made a seamless transition to the hybrid.

Update:  I learned about the hybrid origins of our local Sycamore street tree in an urban forestry class at UC Berkeley.  Peter Del Tredici has sent me this correction: “The london plane tree, Platanus x acerifolia is generally considered to be a hybrid between the european species, P. orientalis and the eastern species, P. occidentalis. the west coast species, P. racemosa is not part of the mix.”   

Western tiger swallowtail. Wikimedia

  • Spartina alterniflora is a marsh grass that is native on the East Coast. It grows taller and denser than our native marsh grass, Spartina foliosa that also dies back in winter, unlike the East Coast native that does not.  In other words, non-native spartina is superior protection from winter storm surges compared to native spartina.  Yet, non-native spartina is being eradicated using herbicides along the entire West Coast of the country because it hybridizes with the native spartina species.  The herbicide used for that purpose has been sprayed for about 15 years, which is probably why attempts to plant native spartina as a replacement have been unsuccessful.  The result of the eradication project has been bare mud that provides no protection from erosion caused by rising sea levels and more intense winter storms.  In other words, if non-native spartina were permitted to hybridize with native spartina on the West Coast, the result would be a new species that is better adapted to face the threats of rising sea levels and intense storm surges.

Doug Tallamy’s closing photo of his keynote speech to the California Native Plant Society Conference, 2018

Fear of hybridization is akin to fear of mongrelization–the mixing of races–by racists and xenophobes.  It is closely related to the fear of non-native plant and animal species, a short-step away from the fear of human immigrants.  Concern about racial purity is not far from fear of “genetic pollution.”  State laws in the US prohibiting interracial marriage were not repealed until 1967, when the US Supreme Court ruled in Loving v. Virginia that such laws were unconstitutional in the 16 states in which these laws still remained.  These are cultural fears, not grounded in biological science. 

In conclusion

Doug Tallamy’s intended audience is home gardeners.  Although he urges his readers to remove invasive species, he does not endorse the use of herbicides.  Unfortunately, his work is used by public land managers to justify their eradication projects that usually use herbicides.  If Tallamy’s work stayed in its home gardening lane, it would do less damage to the environment.

Eradication of marsh grass on East and West Coasts doesn’t make sense

New York State agencies have been trying to destroy the Piermont Marsh since 2013, because most of the marsh grass is not native. Piermont Marsh is adjacent to the small village of Piermont on the west side of the Hudson River, less than 30 miles north of New York City.

The community of Piermont organized to prevent the destruction of their marsh for two reasons:

  • They believed that the marsh had protected them from the devastating storm surge caused by Hurricane Sandy in 2011. The village sustained damages of $11.8 million in that storm, but villagers believed it would have been much worse without the protection of the marsh.
  • The initial plan to eradicate 200 acres of non-native phragmites proposed the use of herbicides to kill the marsh grass. The villagers were concerned about large quantities of herbicides being sprayed into their waterways.

The Piermont Marsh is also very beautiful.

I have followed the attempt to save the Piermont Marsh because it is nearly identical to our West Coast version of the same issue.  Non-native spartina grass has been nearly eradicated on the entire West Coast using herbicides over the past 15 years.  After witnessing the unintended consequences of the eradication of spartina, I was sympathetic to the community of Piermont and hopeful that their organized resistance might be successful.

Opposition to the proposed project to destroy the Piermont Marsh has accomplished a great deal.  The first round of public comment and negotiation resulted in a reduction in the size of the project from 200 acres to 40 acres.  The Piermont community was also given a commitment to conduct an analysis of the damage done to the village by the destructive storm surge in the 2011 hurricane Sandy to determine the role the marsh played in protecting the village from even greater damage.

The scientist who conducted that study reported the results of the study in July 2020.  He concluded that “the presence of the Marsh is estimated to have avoided $902,000 worth of property damage and loss.” (1) He made other significant observations:

  • The native marsh grass that the project wishes to restore does not provide as much storm protection in the spring: “Typha [the native species of marsh grass] shows far more seasonal variation than phragmites.  Unlike phragmites, which maintains its height and density year-round, Typha is shorter and sparser in the spring.” (1)
  • The scientist predicted that by 2100 the Piermont Marsh will likely be overwhelmed by sea level rise. Whatever vegetation is at the Piermont Marsh, it will be gone within 80 years.

For the moment, the Piermont Marsh project is on hold:  “[The plan] will be redrafted and the new draft should be presented to the public in 2021.” (1) Meanwhile, herbicides will not be used in the marsh and experiments will be conducted to kill marsh grass by covering it with a geotextile that deprives the vegetation of light.  However, project managers have not made a commitment to avoid herbicides in the future.

Based on my experience with opposition to such destructive projects,  delays are often ultimately victories.  Funding priorities often change and more scientific information becomes available to inform a better decision.  For example, the current draft plan contains outdated information about glyphosate.  It claims that “Glyphosate is a non-selective, systemic herbicide that controls weeds by inhibiting a specific pathway for amino acid synthesis that is unique to plants and not present in animals.”

We now know that the claim about a “unique pathway” for glyphosate existing only in plants is not true.  In 2020, plaintiffs in a class-action suit against Monsanto alleging that it falsely advertised that the active ingredient in Roundup only affects plants were awarded $39.5 million.  The settlement also requires that the inaccurate claim be removed from the labels of all glyphosate products: “…[plaintiff] says Monsanto falsely claimed through its labeling that glyphosate, the active ingredient in Roundup, targets an enzyme that is only found in plants and would therefore not affect people or pets. According to the suit, that enzyme is in fact found in people and pets and is critical to maintaining the immune system, digestion and brain function.”

In defense of phragmites

According to a study conducted in 2017, phragmites is playing the same ecological roles as their native predecessors:

“An invasive species of marsh grass that spreads, kudzu-like, throughout North American wetlands, may provide similar benefits to protected wetlands as native marsh grasses. According to new research from North Carolina State University, the invasive marsh grass’s effects on carbon storage, erosion prevention and plant diversity in protected wetlands are neutral… studies have shown that Phragmites may help reduce shoreline erosion in marshlands and store carbon at faster rates than native grasses…The team found no significant differences between ecosystem services of the marshes they studied, indicating that Phragmites’ effect was largely neutral.” 

Land managers and contractors have been trying to eradicate phragmites in the Delaware River and its estuary for nearly 40 years.  Although the contractors are still committed to that project, critics are getting louder and scientists are finding more evidence of the benefits of phragmites.  It is no longer clear that eradicating phragmites is possible, nor is it clear that it would be beneficial.

Rising sea levels as ice melts in warmer temperatures are bringing the benefits of phragmites into focus:  “Some scientists have been arguing that phragmites…could be a key line of defense against rising sea level, particularly in areas like the Mid-Atlantic where land is sinking while water continues to rise… Research from 20 years ago found that phragmites help marshes elevate faster than some other plants…”

The herbicides used to kill phragmites are aerial sprayed from helicopters, killing both native and non-native plants, resulting in barren mudflats that are more vulnerable to erosion:  “The herbicide treatment of phragmites can also mean other native plants become casualties in the process, leaving an unvegetated landscape behind. With no plants to hold sediment in place, an open mudflat can be extremely vulnerable to flooding in the face of storms or unsuccessful regrowth… ‘You know, the Phrag marsh is certainly a whole lot better than no marsh,’ [a Rutgers scientist] said.”

Trying to eradicate phragmites no longer makes sense.  So why is it continuing to happen?  A Rutgers marine biologist explains:   “Well, might I say…there’s a whole army of environmental consultants that get paid to remove phragmites and don’t get paid to leave it alone.”  That is really the heart of the matter.  The projects are designed to create jobs and apply for government funds, not to protect the environment.

The West Coast version of marsh grass eradication

If the word “spartina” is substituted for the word “phragmites” the Piermont Marsh project and the questions it raises apply to similar projects on the West Coast.  For over 15 years, non-native spartina marsh grass has been eradicated using herbicides along the entire West Coast.  The result of spartina eradication projects on the West Coast is also barren mud shoreline that is poisoned with herbicide and miles of coastline that is vulnerable to rising sea levels and erosion.

The Ridgway Rail was collateral damage of the spartina eradication project. The population of this endangered bird plummeted because its nesting habitat was destroyed.

There is another similarity between the East Coast and West Coast versions of eradicating marsh grass.  Like the native typho (cattail) that is the goal of the East Coast project, native spartina that was the goal of the West Coast project is inferior protection of the coastline against storm surges.  The native species of spartina on the West Coast that was the theoretical goal of the eradication project is shorter and less dense than the non-native species.  It also dies back in the winter, unlike the non-native species that persists throughout the year.  In other words, the native species does not provide the same protection for the shoreline that is provided by the non-native species.  In any case, plantings of the native species failed in the poisoned ground, so its benefits claimed by the project are entirely irrelevant.

These eradication projects don’t make any more sense on the West Coast than their mirror image on the East Coast. 


  1. The Piermont Marsh Alliance Report on July 16 Webinar regarding Piermont Marsh

“Restoration” projects in the Bay Area are more destructive than constructive

I began studying the native plant movement and the “restoration” projects it spawned over 20 years ago when I learned about a proposal to change my neighborhood park in San Francisco in ways that were unacceptable to me.  Virtually all the trees in the park were non-native and the original proposal would have destroyed most of them.  The trees provide protection from the wind as well as a visual and sound screen from the dense residential neighborhood.  A treeless park in a windy location is not a comfortable place to visit.

The original plans would have made the park inhospitable to visitors for several other reasons, particularly by reducing recreational access to the park.  The prospect of losing my neighborhood park turned me into an activist.  I eventually learned there were similar plans for most major parks in San Francisco.  My neighborhood organized to prevent the destruction of our park and to some extent we succeeded.  However, we were unable to prevent the city-wide plan from being approved in 2006, after fighting against it for nearly 10 years.

When I  moved to the East Bay, I learned that similar projects are even more destructive than those in San Francisco,  I have spent the last 20 years informing myself and others of these plans, visiting those places, and using whatever public process that was available to oppose the plans.  The following paragraphs are brief descriptions of the projects I have studied for over 20 years.

Tree Destruction Projects in the East Bay

East Bay Municipal Utilities District (EBMUD) is the public utility that supplies our water in the East Bay.  To accomplish that task, EBMUD manages 28,000 acres of watershed land.  Like most open space in the Bay Area, the vegetation on EBMUD’s land is a mix of native and non-native species.  EBMUD destroys non-native trees which it believes to be a fire hazard.  EBMUD uses herbicides to “control” non-native vegetation, but it does not use herbicides on tree stumps to prevent resprouting.  EBMUD reports using 409 gallons of herbicide and 6 gallons of insecticide in 2019.  Of the total amount of herbicide, 338 gallons were glyphosate-based projects.  EBMUD says “minor amounts of rodenticide were applied by contractors.”

The East Bay Regional Park District (EBRPD) approved the “Wildfire Hazard Reduction and Resource Management Plan” and its Environmental Impact Report in 2009.  This plan is removing most eucalyptus, Monterey pine, and acacia from several thousand acres of parkland.  Forests are being thinned from an average density of 600 trees per acre to approximately 60 trees per acre.  These plans are being implemented and funding for completion of the project has been secured.  Herbicides are used to prevent the trees from resprouting and to destroy vegetation deemed “invasive.”

UC Berkeley clear-cut over 18,000 non-native trees from 150 acres in the Berkeley hills in the early 2000s.  UCB applied for a FEMA grant to complete their clear-cutting plans.  The FEMA grant would have clear cut over 50,000 non-native trees from about 300 acres of open space in the Berkeley hills.

Frowning Ridge, UC Berkeley, 2010

In 2016, FEMA cancelled grant funding as a result of a lawsuit and subsequent appeals from UCB were defeated several years later.  In 2019, UCB revised its original plans.  With the exception of clear-cutting ridgelines, the revised plan will thin non-native forests.  Herbicides will be used to prevent the trees from resprouting.

The City of Oakland applied for a FEMA grant in collaboration with UC Berkeley to clear cut non-native trees on over 120 acres in the Oakland hills.  That FEMA grant was cancelled at the same time UC Berkeley lost its grant funding.  Oakland has also revised its plans for “vegetation management” since the FEMA grant was cancelled.  The revised plan will thin non-native forests on over 2,000 acres of parks and open space.  The plan is undergoing environmental review prior to implementation.  Herbicide use to implement the plan is being contested.

Tree Destruction Projects in San Francisco

The Natural Areas Program (now called Natural Resources Division) of the City of San Francisco has destroyed thousands of trees in 32 designated areas of the city’s parks since the program began in 1995.  The management plan for the Natural Areas Program was approved in 2006, after 10 years of opposition.  The plan proposes to destroy an additional 18,500 trees over 15 feet tall and untold numbers of smaller trees that the plan chooses not to define as trees.   Herbicides are used to “control” non-native vegetation and prevent trees from resprouting after they are cut down.

Sutro Forest 2010

University of California at San Francisco (UCSF) began its effort over 20 years ago to destroy most non-native trees on 66 acres of Mount Sutro.  UCSF applied for a FEMA grant to implement those plans based on their claim that the Sutro Forest is a fire hazard.  UCSF withdrew the grant application after FEMA asked for evidence that the forest is a fire hazard.  San Francisco is cool and foggy in the summer, making fires rare and unlikely.

Sutro Forest with resprouts of destroyed trees. November 2019

UCSF’s plans to destroy most trees on Mount Sutro were approved in April 2018.  Many trees on Mount Sutro have been destroyed since the project was approved and more will be destroyed before the project is complete.  UCSF made a commitment to not use pesticides in the Sutro Forest.  Many of the trees that have been destroyed have therefore resprouted.  Unless the resprouts are cut back repeatedly, the forest is likely to regenerate over time.

  Tree Destruction Projects on Federal Lands

The federal government is one of the largest landowners in the Bay Area.  Golden Gate National Recreation Area (75,500 acres), Point Reyes National Seashore (28,800 acres), and Muir Woods National Monument are operated by the National Park Service.  The Presidio in San Francisco is a National Park that is presently controlled by a non-profit trust.  These parks have engaged in extensive tree-removal on the public lands they control.  Information available on their websites does not enable us to quantify the acres or number of trees that have been removed or are planned for removal in the future.  Therefore, we will describe those projects in the broad terms available to us.

There are two main categories of tree-destruction projects on these federal lands.  There are many large-scale “restoration” efforts that have required the removal of all non-native vegetation, including trees.  These attempts to eradicate non-native plants are based on a misguided belief native plants will magically return.  Herbicides are used by National Park Service to destroy non-native vegetation, although specific information is difficult to obtain because NPS is not responsive to inquiries and the federal public records law can take years to respond.

Eradication efforts fail regardless of method used

In “Lessons learned from invasive plant control experiments:  a systematic review and meta-analysis,” scientists analyzed 355 studies of attempts to eradicate non-native plants from 1960 to 2009.  The scientists determined the methods used and the efficacy of those methods.  More than 55% of the projects used herbicides, 34% used mechanical methods (such as mowing, digging, hand-pulling), 24% burned the vegetation, and 19% used all three methods.  The study found that herbicides most effectively reduced “invasive” plant cover, but this did not result in a substantial increase in native species because impacts to native species are greatest when projects involve herbicide application.  Burning projects reduced native coverage and increased non-native coverage. In other words, it doesn’t matter what method is used, eradicating non-native plants does not result in the return of native plants.   We didn’t need a study to tell us this.  We can see the results with our own eyes.

Flammability of plants is unrelated to nativity

The other, larger category of tree-removal projects on these federal lands are the so-called “fuel management projects.”  The flammability of non-native plants and trees is exaggerated in order to justify their destruction.   Native plants are not inherently less flammable than non-native plants.

In fact, native vegetation in California is fire adapted and fire dependent for germination and survival.  The California Native Plant Society recently revised its “Fire Recovery Guide. The Guide now says, “California native plants are not inherently more likely to burn than plants from other areas.”  This statement is the mirror image of what defenders of our urban forest have been saying for 25 years:  “Non-native trees are not inherently more flammable than native trees.”  Both statements are true and they send the same message: flammability is unrelated to the nativity of plants.  “Think instead about characteristics of plants,” according to the CNPS “Fire Recovery Guide.”

There are undoubtedly many other similar projects of which we are unaware.  I report only on projects that I have direct knowledge about and that I have visited.

Why I opposed these projects

The San Francisco Bay Area was nearly treeless before early settlers planted non-native trees.  Non-native trees were planted because they are better adapted to the harsh coastal winds than native trees.  The treeless grassland was grazed by deer and elk and burned by Native Americans to promote the growth of plants they ate and fed the animals they hunted.  Grazing and burning maintained the grassland, preventing natural succession to shrubs and trees.

Native Americans setting grass fire, painting by Frederic Remington, 1908

Modern land use and management policies have suppressed fire and reduced grazing in the Bay Area.  Consequently grasslands are naturally converting to chaparral and scrub.  Although managers of public lands often describe these changes in the landscape as “invasions,” Jon Keeley (Ph.D. biologist, USGS) considers them a natural succession“These changes are commonly referred to as shrub invasion or brush encroachment of grasslands.  Alternatively, this is perhaps best viewed as a natural recolonization of grasslands that have been maintained by millennia of human disturbance.” 

Early settlers planted trees to protect their residential communities and their crops from wind.  The urban forest also provides sound and visual screens around parks that are surrounded by dense residential neighborhoods.  Urban forests are storing carbon that is released as greenhouse gas when they are destroyed. They also reduce air pollution by filtering particulates from the air.

When trees are destroyed, the unshaded ground is quickly colonized by weeds that are then sprayed with herbicide.  Even environmental organizations that support the destruction of non-native trees agree about the results of these projects:

  • The California Native Plant Society predicted the post-project landscape in its written public comment on the Draft Environmental Impact Statement (DEIS) of the FEMA project in the East Bay hills with this rhetorical question: “What mechanism is being instituted by FEMA in this DEIS to guarantee a commitment of money and personnel for management of greatly increased acreages of newly created annual weedy grassland?”
  • The Audubon Society predicted the post-project landscape in its written public comment on the DEIS: “There is no support for the conclusion that native vegetation will return on its own.  This plan may not result in an increase in native trees and plants…Heavy mulching will delay or prevent the growth of native species.”

To summarize:  I am opposed to destroying our urban forests because they perform many important ecological functions, including providing habitat for wildlife.  Furthermore, the herbicides used to destroy the forest and control weeds that thrive in the absence of shade, damage the soil and create unnecessary health hazards to humans and other animals.