Looking for Godot: Finding achievable restoration goals

There are chemical and non-chemical approaches to native plant restoration. Neither succeeds.  Non-chemical methods are labor-intensive, which makes them prohibitively expensive.  Chemicals are cheaper and they kill non-native plants, but they don’t restore native plants because they kill them and damage the soil. Either strategy must be repeated continuously to be maintained. This article is the 25-year story of reaching the conclusion that neither chemical nor non-chemical approaches are capable of restoring native plants on a landscape scale.  Where do we go from here?

In 2014, the California Invasive Plant Council (Cal-IPC) conducted a survey of land managers to learn what methods they were using to control plants they considered “invasive.”  The Cal-IPC survey reported that herbicides are used by 94% of land managers and 62% use them frequently.  Glyphosate was the most frequently used herbicide by far. In 2014, no other eradication method was used more frequently than herbicides.

Frequency of herbicide use by land managers in California to kill “invasive” plants. Source California Invasive Plant Council, 2014

We have learned a great deal about the dangers of herbicides since 2014. 

  • The World Health Organization has categorized the most frequently used herbicide—glyphosate—as a probable carcinogen.
  • The manufacturer of glyphosate, Monsanto-Bayer, was successfully sued by terminally ill users of glyphosate.  These product liability lawsuits resulted in multi-million dollar awards for damages. The awards were reduced on appeal but ultimately upheld.  Monsanto has agreed to pay more than $10 billion to settle close to 100,000 product liability claims. 
  • The US 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 is93% of the total of 1,795 endangered species evaluated by the study. 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. 

How have land managers responded to the dangers of herbicides?

San Francisco’s Recreation and Park Department has increased the use of herbicides in public parks every year since 2016.  In 2020, herbicide use increased significantly from 243 applications in 2019 to 295 applications in 2020.  SF RPD has been spraying herbicides on non-native plants for over 20 years.  They have been using hazardous herbicides on some 50 target plant species year after year. The longer they use them, the more resistance to the herbicides the plant develops.

Herbicides used by Natural Resource Division of San Francisco Recreation and Parks Department. Source San Francisco Forest Alliance based on public records of pesticide use

Chris Geiger, director of the integrated pest management program at the San Francisco Department of the Environment, told San Francisco Public Press that although the city has reduced its use of glyphosate outside parks, it won’t ban glyphosate because it hasn’t found a more efficient or safer alternative for controlling some weeds. He said, “In habitat management, there are certain plants you cannot remove from a natural area by hand.”

San Francisco’s IPM program recently published  “Pest Prevention by Design Guide” that illustrates the bind they are in with respect to promoting native plants while trying to reduce pesticide use.  On the one hand, the Guide promotes the use of native plants in landscape design plans by making the usual claim that “Native species are generally best suited to supporting local insect populations and ecosystems.”  On the other hand, the Guide recommends the use of “pest resistant” species that are not eaten by insects and grazing animals and are capable of outcompeting weeds.  Can’t have it both ways, folks!!  

East Bay Regional Park District has made a commitment to phase out the use of glyphosate in developed areas such as parking lots, playgrounds and picnic areas.  However, EBRPD remains committed to using glyphosate and other herbicides to eradicate non-native plants on undeveloped park land. In 2020, no glyphosate was used in developed areas, but about 23 gallons of glyphosate were used to eradicate non-native plants on undeveloped park land. Twenty-one gallons of triclopyr were also used to eradicate non-native shrubs and to prevent non-native trees from resprouting after they were cut down. They continued the 15-year effort to eradicate spartina marsh grass with imazapyr. A few other selective herbicides were used on other eradication projects. (2)

In the San Francisco Bay Area, most land managers are still committed to using herbicides, particularly in so-called “natural areas,” regardless of the damage herbicides do to human health, wildlife, and native plants.  In fact, the City of Oakland is planning to begin using herbicides on 2,000 acres of public parks and open spaces for the first time to implement its vegetation management plan.  The vegetation management plan is both a fuels reduction program and a “resource protection” program, which is a euphemism for native plant “restoration.”

Given what we now know about the dangers of herbicides, why are public land managers still committed to using herbicides?  The City of Oakland explains in the EIR for its vegetation management plan why it is proposing the use of herbicides where they were prohibited in the past:

“It is estimated that if the City were to rely on hand removal and mechanical treatments in place of herbicide, it would cost the City up to 40 times more to treat these areas than under the VMP. The cost for herbicide treatments, not including any associated physical treatments, is approximately $250-$500 per acre. This reflects a range of potential vegetation conditions, vegetation types, and densities. The cost for hand removal and mechanical treatments is estimated at approximately $1,000-$4,000 per acre, using the same range of site-specific conditions.” (page 5-9)

In other words, herbicides are the preferred method of killing non-native plants because it is the cheapest method.  However, there is another reason why herbicides are preferred to non-chemical methods.  There isn’t a non-chemical method that is more effective than using herbicides.

Looking for an alternative to herbicides

As we should expect, new information about glyphosate has increased the public’s awareness of the dangers of pesticides.  California Invasive Plant Council has responded to the public’s growing awareness and concern about the herbicides to which they are exposed in our public parks and open spaces.  They recently published a comprehensive 300-page brochure entitled “Best Management Practices for Non-Chemical Weed Control.”  (1) Many highly qualified land managers participated in the preparation of this credible publication.  The Cal-IPC brochure is credible because it frankly admits that no method of eradication is without problems.  Irrigation and intensive planting are required for good results, but without continuing regular maintenance the results are only temporary.  Few land managers have the resources needed for success.

If you wonder why herbicides are the preferred method of eradicating non-native plants, reading Cal-IPC’s brochure about non-chemical methods will tell you why.  There is no non-chemical method that achieves better results than using herbicide. 

Herbicides are not a magic bullet

Herbicides are the most frequently used method of killing non-native plants, but using herbicides does NOT result in a native landscape.  “Lessons learned from invasive plant control experiments:  a systematic review and meta-analysis,” analyzed 355 studies published from 1960 to 2009 to determine which control efforts were most effective at eradicating the target plants and which method was most successful in restoring native plants. The analysis found that “More than 55% of the studies applied herbicide for invasive plant control.” Herbicides were most effective at reducing invasive plant cover, “but this was not accompanied by a substantial increase in native species,” because, “Impacts to native species can be greatest when programs involve herbicide application.”  It’s not possible to kill non-native plants without simultaneously killing native plants and damaging the soil.

Reaching a dead—and deadly—end

Public land managers in the San Francisco Bay Area have been trying to restore native landscapes for over 25 years.  Every project begins by eradicating non-native plants, usually with herbicides.  Our public parks have been poisoned repeatedly, but native landscapes have not replaced the plants that were killed.  Meanwhile, we have learned that herbicides are dangerous to our health and animals who live in our parks. 

Oyster Bay is a park in San Leandro that was built on a former garbage dump on landfill in the San Francisco Bay.  The garbage was capped with barren soil and many acres were planted with native bunch grass, as shown in these photos.  This “restoration” method is called competitive planting. The bunch grasses did not survive and the ground was quickly colonized by weeds that were then sprayed with herbicides. 

The only viable alternative to using herbicides to “restore” native plants is to change the goals for native plant restorations such that herbicides won’t be required: 

  • An exclusively native landscape cannot be achieved where native plants have never existed, such as the many parks along the bay waterfront that were built on landfill.  It is an unrealistic goal.
  • Given that no effective method of achieving this unrealistic goal has been found after 25 years and the most popular method is poisoning our environment, it is time to stop trying.
  • Smaller, achievable goals must be set.  Landscape scale projects should be abandoned and replaced with small scale projects where native plants already exist. 
  • Smaller areas can be managed without using herbicides because they will be affordable to manage with labor-intensive methods that are more expensive.
  • If smaller projects are more successful, they will be less controversial.  The projects are unpopular partly because they aren’t successful. 

The native plant movement in the San Francisco Bay Area has bitten off more than it can chew.  Native plant advocates need to back out of their dead end and regroup with plans that are less destructive and more realistic.  As the Economist magazine said in 2015, “you can garden in a garden, but you can’t garden nature.”


(1) California Invasive Plant Council is offering free video training for non-chemical methods of killing “invasive” plants on May 4, 2021, 1-5 pm.  Sign up HERE. 

(2) 2020 IPM Report, East Bay Regional Park District available HERE.   

Nobody cares where a pretty wildflower is from

The feel-good ending of the local news broadcast on Channel 7 (ABC) on February 17, 2021, featured this video of a huge field of oxalis (Bermuda buttercup, Oxalis pes-caprae) blooming on the roadside of Highway 1 in Santa Cruz County.  People were stopping along the road to admire the bright yellow blooms of spring and photograph them.  No one said anything about where the plant “belongs,” and no bad words were spoken about this useful plant that native plant advocates love to hate.

Click on the picture to activate the video

Despite its beauty and utility, oxalis is sprayed with one of the most toxic herbicides on the market in public parks and open spaces in the Bay Area.  San Francisco’s Recreation and Parks Department has been spraying oxalis in several public parks for over 15 years.  San Francisco Forest Alliance (SFFA) published a brilliant article about this pointless and destructive crusade that was republished by Conservation Sense and Nonsense in 2015.  That article about the many benefits of oxalis is one of the most popular articles on this blog; it has been viewed by over 10,000 readers and many more on the SFFA website.  We invite you to visit it and we summarize it briefly here:

  • Oxalis blooms briefly in early spring and dies back before summer begins, leaving the ground to other plants. It does not kill other plants, rather it co-exists briefly during its annual bloom.
  • Oxalis is very useful to pollinators and its tuberous roots (bulbils) are eaten by ground dwelling animals such as gophers.
  • Oxalis is called sour-grass because of its pleasant-tasting tang and it is often eaten by children.
  • Triclopyr is the active ingredient in the herbicide that is used on oxalis during its blooming season. It damages the soil by killing beneficial fungi and microbes, and it is toxic to many animals.

The annual poisoning of oxalis on Mount Davidson was recently videotaped by Ron Proctor and published by the San Francisco Forest Alliance. A crew of 5 men was hired to do the deed.  Ironically, this spraying of oxalis on Mount Davidson in San Francisco was taking place at the same time that tourists were admiring oxalis in a neighboring county.

Click on picture to activate the video.

Oxalis is not an isolated example of a non-native plant that is admired by the public, but hated by native plant advocates and public land managers who do their bidding.  As a member of the Sierra Club, I receive emails alerting me to opportunities to advocate for the protection of the environment.  The most recent email featured a picture of a yellow wildflower in the foreground of a photograph of a Bay Area landscape:

The yellow wildflower in the foreground is Black Mustard (Brassica nigra).  I responded to the Sierra Club’s email:

“The plant in the foreground of your photograph appears to be Brassica nigra:  ‘Brassica nigra, or black mustard, is an annual plant cultivated for its black or dark brown seeds, which are commonly used as a spice. It is native to tropical regions of North Africa, temperate regions of Europe, and parts of Asia.’ Wikipedia

“I hope the use of this photo in this Sierra Club email to its members means that the Sierra Club is finally prepared to accept the reality of the presence of non-native plants in our public parks and open spaces.  The Sierra Club’s support for unnecessary and destructive eradication projects has been regrettable, particularly because they require the use of harmful herbicides.  I hope this email is an indication that the Sierra Club is finally ready to reconsider this futile crusade.”

I received this disappointing reply from the Sierra Club:  The staffer who puts together our newsletter isn’t a plant buff and wouldn’t have known the difference. But I am a plant buff and review the newsletter and know the difference between a mustard and a native plant. I somehow just overlooked that photo entirely. Thanks for bringing it to my attention. I’ll be more careful in my review of the newsletter in the future (look more carefully at the photos). And we’ll change the online version.”

The beauty and resilience of weeds

Dandelion by Mona Caron. Click on the picture to see more murals by Mona Caron.  Mona is a Swiss artist who became a muralist in her adoptive hometown San Francisco, California.  She is best known for her multi-story murals celebrating the rebellious resilience of weeds.

 The Bottom Line

The general public doesn’t care where plants came from.  The public recognizes and values beauty wherever it is found.  Unfortunately, our public lands are in the death grip of the native plant movement and environmental organizations that should be objecting to the use of herbicides in our public parks and not promoting that destructive agenda.  The crusade against non-native plants has been responsible for spraying our public lands with dangerous pesticides for over 20 years.  They have little to show for their toxic crusade, perhaps because the herbicides damage the soil and make the survival of native plants even less likely.


The featured photo at the top of this article was taken in Glen Canyon, another public park in San Francisco where oxalis has been sprayed annually for many years.  The copyright photo of a coyote in a field of oxalis was taken by Janet Kessler and is shown with her permission.

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.

Final chapter for Oakland’s Vegetation Management Plan? Maybe not.

The draft Environmental Impact Report (DEIR) for Oakland’s Vegetation Plan (OVMP) has been published.  When the DEIR is approved and funding is identified, implementation will finally begin after a process that began four years ago.  The plan and its EIR are available HERE.  The deadline for public comments on the DEIR is January 22, 2021.  The email address for submitting public comments is DEIR-comments@oaklandvegmanagement.org

The primary purpose of the plan is to reduce fire hazards in High Fire Hazard Zones in Oakland by reducing fuel loads on about 2,000 acres of public land and 300 miles of roadside.  Although there were many issues, the primary battle lines were drawn by these issues at the beginning of the process and they remain:

  • On one side, some people were concerned by the scale of tree removals that were considered and the herbicides that would be needed to control the resprouts of the trees after removal. If the plan as proposed is approved, herbicides will be permitted in places where they were prohibited in the past.
  • On the other side, some survivors of the 1991 Oakland wildfire and native plant advocates who are their allies, want all non-native trees to be destroyed and replaced with native plants. They are not satisfied with plans to thin trees around structures and roadsides.

The consequences of destroying Oakland’s urban forest

The survivors of the 1991 fire in Oakland asked that the OVMP be radically revised at a public hearing about the OVMP DEIR on December 16, 2020.  They called their version of a vegetation management plan Alternative 5.  It is an alternative that does not exist in the DEIR.  These are the major elements of what they asked for:

  • They ask that all non-native trees be destroyed everywhere in the treatment areas. They ask that the trees be clear-cut rather than thinned, as proposed by the plan. They ask that tree removals not be confined to defensible space around structures, as proposed by the plan.
  • They ask that removed trees and non-native vegetation be replaced with native trees and vegetation.
  • They ask that roadside clearance of vegetation occur 100 feet from both sides of the road rather than 30 feet as the OVMP proposes.
  • They expressed concern about dead trees. They are apparently unaware of the epidemic of Sudden Oak Death that has killed 50 million native oaks in the past 15 years and is spreading rapidly.

The OVMP DEIR is responsive to some of these concerns. 

  • The OVMP DEIR makes a commitment to seeding areas that are steep and barren after vegetation removal with seeds of native plants. The purpose of this seeding is to minimize the potential for erosion.
  • The OVMP DEIR makes a commitment to replant trees removed in riparian areas as required by Oakland’s ordinance to protect creeks.
  • The OVMP makes a commitment to remove all dead trees in treatment areas. Sudden Oak Death (SOD) is the probable cause of the dead trees described at the public hearing.  SOD has been found in many treatment areas in the plan:  Garber Park, Shepherds Canyon, Dimond Canyon Park, Joaquin Miller Park, Leona Heights Park, Knowland Park, and Sheffield Village. (OVMP DEIR 3.4-87)

Increasing roadside clearance to 100 feet would increase the acreage of roadside tree removals and vegetation required by the OVMP by 233%.  The consequences of such extensive removals can be seen on Claremont Ave, west of Grizzly Peak.  These removals were done by UC Berkeley.  Catastrophic erosion after intense rainfall looks inevitable.

Claremont Ave, West of Grizzly Peak Blvd. November 2020

Huge piles of wood chips and logs must be disposed of.  Such piles of wood chips are known fire hazards until they are spread or disposed of.  The wood chip piles resulting from roadside clearance on Claremont Ave cannot be spread because the quantity exceeds available land.  UC Berkeley has made a commitment to build a biofuels plant to burn the wood chips to generate electricity for campus facilities.  The OVMP does not make a commitment to build a biofuels plant to properly dispose of wood chips and it mandates a limit of 6 inches of wood chip mulch on the ground. Please look at these pictures of some of the wood debris created by clearcutting less than one mile of roadside on Claremont Ave.  Then consider that the OVMP proposes to treat 300 miles of roadside.  Multiply these piles of wood chips and logs by 300 to consider the consequences of “Alternative 5.”

Update:  Since publishing this article, I have learned that UC Berkeley has NOT built a biofuels plant to dispose of the wood debris to meet Cal Fire grant requirements for reducing greenhouse gas emissions.  Nor does UC Berkeley intend to build a biofuels plant.  The disposition of the wood debris from this project has not yet been determined.  This is the final paragraph of my formal complaint to Cal Fire about this project:  “In conclusion, the grant application for this project makes a commitment to reducing greenhouse gas emissions that is based on the assumption that a biofuels plant will generate electricity from the wood debris.  Such a plant has not been built and UC Berkeley apparently does not intend to build such a plant.  Other claims made in the grant application about carbon storage are based on inaccurate claims about carbon storage.  Grant guidelines state, “Failure to meet the agreed upon terms of achieving required GHG reduction may result in project termination and recovery of funds.”  In other words, Cal Fire should terminate this project and recover any funds that have been remitted to UC Berkeley.  The project is a misuse of grant funds because it will increase fire hazards and increase greenhouse gas emissions.  Without imputing motives, on the face of it, the grant application looks fraudulent.” The full story of how this project has violated grant guidelines as well as the description of the project itself in the grant application is told HERE.  January 18, 2021 

One of many piles of wood chips, Claremont Ave, November 2020

One of many piles of wood chips, Claremont Ave, November 2020

One of many piles of logs, Claremont Ave., December 2020. Photo by Doug Prose, courtesy Hills Conservation Network.

Oakland does not want a biofuels plant because it will significantly increase pollution.  Sierra Club Magazine reports that “The manufacturing of biomass-energy wood pellets requires drying the logged material in a wood-fired process, then pressing the dried wood into pellets—and every step emits significant amounts of air pollution. According to the Environmental Integrity Project study, the emissions from the facilities include fine particulate matter, nitrogen oxides, carbon monoxide, and volatile organic compounds. Wood-pellet manufacturing emits a form of soot and dust called PM 2.5, which can pass deep into the lungs and depress lung function, worsen asthma, and cause heart attacks. Volatile organic compounds, when exposed to sunlight, transform into ozone, which is especially dangerous to children and the elderly.”

This aerial view of the clear cut on Claremont Ave makes it clear that this is a native plant “restoration,” not fire hazard mitigation.  The north side of the road has been clear cut 100 feet from the road where the trees were non-native.  There has been no comparable clearance on the south side of the road where the trees are native.  The native trees are predominantly native bay laurels that are known to be highly flammable.  The leaves of bay laurel contain more oil than the leaves of eucalyptus and the branches grow to the ground, providing a fire ladder to the tree canopy.  If fire hazard mitigation were the goal of this project, both sides of the road would have been treated the same.

This picture of the Claremont Ave project was taken from the west December 2020.  Photo by Doug Prose, courtesy Hills Conservation Network.

The cost of Alternative 5 would be prohibitive. The plan would need to be rewritten and a new EIR prepared.  The first plan took four years to prepare; the second will take nearly as long after new funding is secured for it. Funding for implementing the OVMP has not been identified.  The City of Oakland is currently running an annual budget deficit of $62 million.  Budget cuts are planned to address the deficit, including 10 mandatory furlough days for police and firemen.

One of many reasons why I love my home, Oakland, is its deep commitment to equity.  If Oakland had the resources to fund restoration of approximately 2,000 acres of public land and 300 miles of roadside to native vegetation, it is unlikely to spend those resources in the wealthiest communities in Oakland on a project that would bring little benefit for the poorest communities in Oakland.  Oakland’s Equitable Climate Action Plan (ECAP) is a case in point.  Its forestry section is devoted to planting trees in the poorest neighborhoods that suffer the most air pollution and have the fewest trees, as it should be.

I am sympathetic to the survivors of the 1991 Oakland fire as well as to those who have been injured by chemicals to which they were exposed.  Fire survivors have had a traumatic experience that has irrevocably altered their perception about the causes of wildfire.  There are also other survivors of the 1991 fire who watched native redwoods and oaks burn.  Their understanding of wildfire is therefore different, but it is more consistent with the wildfires of the past 5 years that have occurred in predominantly native vegetation.  Native vegetation in California is fire adapted and fire dependent.  Non-native vegetation is not inherently more flammable than native vegetation.

Public Policy requires compromise

Thinning of non-native forests and herbicide treatment to prevent resprouting is not without risks.  We will lose some of our protection from wind.  The trees that remain will be more vulnerable to windthrow.  There may be some erosion in steep areas.  The herbicide that is usually used to prevent resprouts (triclopyr) kills tree roots by traveling from the freshly cut stump through the roots of the tree.  The roots of trees are intertwined with the roots of their neighbors that are often damaged by the herbicide and sometimes killed.  The herbicide kills mycorrhizal fungi that live on the roots as well as microbes in the soil.  Their loss reduces the health of the soil, handicapping the survival of remaining and new plants. This damage to soil is one of many reasons why native plant “restorations” are frequently unsuccessful after scorched earth eradications. Both triclopyr and imazapyr are on the list (California Code of Regulations 6800) of pesticides that have “the potential to contaminate groundwater” because they are very mobile and persistent in the soil.

I accept these risks in the interests of reducing fire hazards.  I have asked for a few tweaks to the plan, including continuing to prohibit foliar spraying of herbicides in public parks and open spaces.  These are the compromises that must be made to make public policy.  We cannot paralyze ourselves by letting the perfect be the enemy of the good.  Oakland needs a Vegetation Management Plan that is effective, affordable, and safer than other alternatives.  That’s what the Oakland Vegetation Management Plan is. 

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.

Invasion Biology vs. The “Restoration” Industry

Daniel Simberloff gave the keynote address to the symposium of the California Invasive Plant Council (Cal-IPC), entitled “Invasive Species Denialism and the Future of Invasion Management.”  Simberloff is the most vocal academic defender of invasion biology.  His presentation to Cal-IPC contains interesting clues about more effective strategies for the critics of invasion biology, of which I am one.  In a nutshell, Simberloff dismisses critics easily with a few waves of his hand, but he stumbles when faced with the economic and ecological costs of the methods used to eradicate so-called “invasive species.”  He can defend the theoretical hypotheses of invasion biology, but he finds it difficult to defend the “restoration” industry that invasion biology spawned, specifically the use of pesticides.

Simberloff opened his presentation with this rogue’s gallery of the critics of invasion biology.  Some readers will recognize some of these “deniers.”  If not, you might recognize some of the many books the “deniers” have published.

Simberloff categorized the criticisms of invasion biology then flipped them off, one by one.  Keep in mind as you read Simberloff’s summary that it does not do justice to the actual criticisms of invasion biology.

  • Critics say that most non-native species aren’t harmful.
    • Simberloff says we don’t know how harmful non-native species are because few are studied, their impacts are often subtle, and there is often a time lag before they become harmful. He believes that all non-native plants are potentially harmful to ecosystems.
  • Critics say that some non-native species are beneficial.
    • Simberloff says that critics only report the benefits, while ignoring the negative impacts of non-native species.  (Actually, most critics are proposing a cost/benefit analysis that acknowledges both positive and negative impacts.)
  • Critics say that invasion biology is xenophobic.
    • Simberloff says that if you’re looking for xenophobia, you often see it. He calls this the “law of instrument” or if your instrument is a hammer, everything looks like a nail.  (Frankly, I didn’t understand the point he was trying to make, but I have tried to describe it accurately based on what he said.)
  • Critics say that trying to eradicate non-native species is futile.
    • Simberloff says this argument ignores the progress that has been made in the technology of eradication methods. He used the “early detection and rapid response” strategy as an example of progress in eradicating non-native plants.  That strategy focuses on small populations of non-native plants, basically acknowledging the futility of trying to eradicate large areas of well-established non-native plants.
    • Much of Simberloff’s presentation was devoted to describing many developments in genetic engineering, such as CRISPR to drive species to extinction and gene silencing. All of the examples of such developments were aimed at killing insects (such as mosquitoes) and animals (such as rats and mice), with one exception. He was particularly enthusiastic about island eradications of which there are hundreds, and hundreds more on the drawing boards.  Only one gene-editing project on plants is trying to develop a genetic method to eradicate phragmites.

Things finally became interesting, when Simberloff took questions:  “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.”

The Executive Director of Cal-IPC recognized the dangers of Simberloff’s answer because pesticides are the primary tool used by the “restoration” industry and much of the conference was devoted to telling over 650 employees of the “restoration” industry about new developments in pesticide use.  Those new developments are not good news to those who are concerned about the dangers of pesticides.  For example, a new “drizzle” technique increases the concentration of the active ingredient and lowers the volume of the application, increasing toxicity of the application.  Another alarming presentation described the use of drones to spray herbicides on hundreds of acres of phragmites in the Suisun Marsh.

The absence of good alternatives to pesticide use in eradication projects is another source of pressure on the “restoration” industry and therefore on Cal-IPC:

  • Jon Keeley’s presentation about the interaction of fire, fire prevention, and plant invasions included the observation that using prescribed burns to eradicate non-native plants results in more non-native plants, not more native plants.
  • A land manager in Southern California acknowledged that pressures to reduce pesticide use threaten the future of his project: “Natural herbicides result in more time intensive and costly weed control, with less confidence of success. Where herbicide application is completely restricted, other weed control methods like hand weeding or mowing can be implemented successfully, but they often fall short of herbicide in effectiveness. This resulting reduction in effective weed control must be taken into account in future plans for habitat restoration and management, and our existing programs will have to reevaluate the proposed efforts, cost of those efforts, and expectations for success, both short and long term.” (Scott McMillan, abstract)
  • Finally, with the exception of a few timid questions from participants, no mention was made about the threat of climate change on the future of native ecosystems. Simberloff likened critics of invasion biology to “climate change deniers.”  In fact, it’s fair to say that those who demand that we replicate native ranges existing 250-500 years ago are more accurately called climate change deniers.

The Executive Director of Cal-IPC tried to save the day by portraying those who oppose pesticides as extremists, based on what he considers “unscientific” studies.  But Simberloff wouldn’t take the bait.  He wasn’t willing to dismiss the concerns about pesticides.  Instead, Simberloff passed the buck:

“I’ll beg off on answering that question on grounds that I’m not a social scientist or psychologist.  This is not my area of expertise.  There is some reason for the extremists because Monsanto has sometimes lied to us and there have been problems associated with pesticides.  I leave this question to policy scientists.”

Simberloff reveals the flaw in the “restoration” industry

As a critic of invasion biology and the use of pesticides, I have always been frustrated that critics of invasion biology do not use the damage done by eradications as a reason for their criticism.  With the exception of Tao Orion’s Beyond the War on Invasive Species, none of the books written by critics have used this argument.  It is a missed opportunity and Simberloff’s presentation to Cal-IPC is an indication that it is the strongest argument against eradication projects that are inspired by invasion biology.

Invasion biology is a theoretical construct.  It does no harm to ecosystems until it justifies the use of harmful methods to eradicate non-native species.  I humbly ask that critics of invasion biology wake up to this opportunity.  Pesticides are a winning argument against “restoration” projects that eradicate non-native plants.  Any cost/benefit analysis of new eradication projects should include the ecological and economic costs of pesticides in the equation.

Beyond Pesticides points the way forward

I try not to leave the field without offering a compromise because opposition without solutions is not constructive.  I offer this sage advice from Beyond Pesticides about case-by-case evaluations of weed invasions that will reduce damage to ecosystems.  Beyond Pesticides responded to this question:  “I’m working on a pesticide policy in my community and am interested in how you might suggest we deal with “invasive” species. Can you point us in the right direction? Martin, Boston, MA.”  This is BP’s thoughtful answer:

“It’s Beyond Pesticides position that invasives, or opportunistic species, should be dealt with on a case-by-case basis, with established priorities and a plan. With any unwanted species, there needs to be an understanding of the ecological context. We need to be asking the right questions: What role is the plant currently playing in a landscape—what niche is it currently filling? If we remove this plant, what will fill that niche? Will we be replanting the right native species to fill that niche? What are the detrimental impacts of letting it spread? Is there a way we can isolate it to stop its spread? Can we ever remove this plant altogether, or will we be working at control indefinitely? These are important questions that we need to be asking before we even consider management methods. Regarding policy, requiring an individualized invasive species management plan seems to be the right answer, though unfortunately many pesticide reform policies sidestep the issue and simply exempt invasives to avoid opposition. Just like all organic approaches, we’ll want to place a focus on prevention and working with ecological systems, rather than against them, making even least-toxic pesticide use a last resort. There is a strong potential to undermine the stability of an ecosystem if we simply go in and immediately break out the strongest tools in the toolbox without a plant replacement strategy. On a turf system with common weeds a simple answer is grass plants. But, in forested areas already subject to intrusion (from construction/logging, etc.), rights-of-way, and urban areas, the focus is on alternative vegetation or ground cover. Sometimes, little should be done except simple mechanical cutting to keep these species in balance. This is an interesting and, at times, contentious issue that environmentalists grapple with, so there is certainly room for fresh ideas on how to approach opportunistic species without the use of toxic pesticides. For more information, we encourage you to watch the talk given at Beyond Pesticides 37th National Pesticide Forum in New York City by Peter Del Tredici, PhD, senior research scientist at Harvard’s Arnold Arboretum (www.bp-dc.org/ invasives).”

 

Re-upping on Reality

A book review by Marlene A. Condon©of Wild Urban Plants of the Northeast by Peter Del Tredici

Marlene A. Condon is the author/photographer of The Nature-friendly Garden:  Creating a Backyard Haven for Plants, Wildlife, and People (Stackpole Books 2006; information at www.marlenecondon.com).  Please visit her blog, In Defense of Nature.  You can reach her at marlenecondon@aol.com

To the farmer’s eye, Eastern Redcedar trees “invade” his cow fields where he would prefer only grass to grow. To the ecologist’s eye, the trees signify the need for soil remediation. Photo credit Marlene A. Condon

Prefatory Comments

When I was a student in the mid-1970s at Virginia Tech, small farms surrounded the town of Blacksburg. I spent time at many of the cow farms, where I constantly heard complaints by agriculturalists about the Eastern Redcedar (Juniperous virginiana) perpetually invading their fields.

After getting my degree in physics, I moved north to Charlottesville, a 140-mile highway drive through rural areas. In the ensuing decades, numerous small farms were abandoned as it became more difficult for farmers to make a living from them.

On frequent trips back to Blacksburg, I watched as the forsaken cow fields began to fill with cedar trees. Then, as time went on, Autumn Olive (Eleagnus umbellata) shrubs began to show up as well. It took decades for those fields to become a forest of cedars, olives, or a mix of both; succession was a slow process because the soils had been emptied of their nutrients, and they were compacted by the generations of half-ton animals that had trod upon them.

What the farmers didn’t understand in the 70s, and what most people still don’t understand today, is that Mother Nature tries constantly to replenish degraded areas by sending in colonizers—plants capable of growing in and enriching exhausted soil. Because very few kinds of plants can perform this natural restorative work, their presence in an area is a sure sign of impoverished land.

Virginia Cedar, Virginia Pine (Pinus virginiana), and Broomsedge (Andropogon virgincus) comprise the most-common native species that move into old Virginia cow fields, sometimes accompanied by Black Locust (Robinia pseudoacacia) that is somewhat beyond its original range. But Autumn Olive, from Asia, is a far superior restorer. It not only enriches the soil with nitrogen, an essential nutrient for plant growth, but also provides for wildlife far better than these other plants. I can’t think of another species that feeds such an abundance of pollinators in the spring with its fragrant blooms, and birds and mammals in mid-to-late summer with fruits and again in late winter by way of its buds.

Yet Autumn Olive is one of the most despised plants of people going after so-called invasive-plant species, the presence of which in our environment they don’t understand and have misinterpreted. For example, University of Delaware entomology professor Doug Tallamy starts Bringing Nature Home (published in 2007) with an explanation of how he came to write his book: He and his wife had moved seven years earlier to 10 acres in southeastern Pennsylvania where he found “at least 35 percent of the vegetation on our property (yes, I measured it) consisted of aggressive plant species from other continents that were replacing what native plants we did have.”

Despite his knowledge that the area “had been farmed for centuries before being subdivided and sold to people like [him and his wife]”, this entomologist clearly had no clue about the full story of the landscape he had bought. The presence of Multiflora Rose (Rosa multiflora), Autumn Olive, and other much denigrated alien species that occupied about a third of his property revealed a prior history that Dr. Tallamy and other invasion proponents ignore.

The farmer’s land had obviously stood idle for some years, giving the variety of plants mentioned plenty of time to move in to rehabilitate the soil. These alien species didn’t suddenly appear and grow to full size overnight; we know the plants had been growing for a long time because the author tells us: “In places on [his] land, bittersweet…was supported at the base by vines with six-inch diameters.”

They weren’t “taking over the land” by “push[ing] out any existing natives,” as Dr. Tallamy erroneously asserts. Ecological succession is defined as “a gradual and orderly process of change brought about by the progressive replacement of one community [herbaceous plants to woody shrubs] by another until a stable climax [forest] is established.” (1) If Professor Tallamy truly understood how the natural world works, he would realize he can now grow his preferred climax community of native trees only because the alien “invaders” prepared the site for him to do so.

It’s unfortunate that Doug Tallamy’s false version of nature has been given much credence and publicity. Thanks to conservationists and governments at all levels rallying around his contrived version of reality, huge areas of well functioning habitat have been, and continue to be, destroyed throughout the United States. Adding insult to injury, the “mission” to get rid of supposedly invasive plants has usually been accomplished with the use of herbicides deadly to wildlife.

Book review of Wild Urban Plants of the Northeast by Peter Del Tredici

The natural world would currently be in far better shape if years ago the press had instead taken note of urban ecologist and Harvard botanist Peter Del Tredici’s book, Wild Urban Plants of the Northeast (first published by Cornell Press in 2010, with an expanded version out this year). Unlike Dr. Tallamy, Dr. Del Tredici recognizes the substantial modifications to our environment wrought by development and climate change, such as soil degradation that goes hand in hand with construction, and drought that is more severe and more frequent due to climate warming.

Anyone knowledgeable about plants should recognize that these changes are quite consequential for these organisms. Perhaps Professor Tallamy doesn’t “get it” because he’s focused only on insects and knows very little about animal/plant relationships. For example, he erroneously writes (2) that the Tulip Poplar tree (Liriodendron tulipifera) “is one of the least productive forest species in terms of its ability to support wildlife—insects and vertebrates alike.” He doesn’t know Tulip Poplar blooms feed a myriad of insects along with hummingbirds, and its seeds are taken by the Eastern Gray Squirrel and other rodents, as well as birds like the Carolina Chickadee, the mascot for his cause célѐbre.

It’s a shame that Wild Urban Plants of the Northeast is referred to as a field guide on its cover and in advertisements. People are bound to think this book is mainly for identification of plants growing in urban areas, but it is so much more. Conservationists and gardeners throughout the entire country—and certainly students learning about plants—would do well to read the 29-page “Introduction”.

 The true value of this work lies in the author’s explanatory text about why the 268 covered species show up in the cracks and crevices of city sidewalks and deserted parking lots, as well as from the walls of decrepit buildings. It’s an ecology lesson that is far more illustrative than the dry text you might read in a book devoted to the subject for the classroom.

An urban Krakatoa. This sea of urban blacktop is like a volcanic lava flow, and the plants that grow here, including mullein (Verbascum thapsus) , chicory (Cichorium intybus), New England hawkweed (Hiercium saubadum), and white heath aster (Symphyotrichum pilosum), can tolerate extreme heat and drought.  Courtesy Peter Del Tredici

For example, in Wild Urban Plants, the reader views a photo of an abandoned building with its fissured parking lot in which a variety of wildflowers grow. The caption likens the “sea of urban blacktop” to “a volcanic lava flow” where plants must be able to tolerate extreme heat and drought. What a superb metaphor! It conveys the environmental conditions to which these plants are subjected while also making very clear to the reader why only certain plants germinate and survive well in such places.

Princess Tree (Paulownia tomentosa) colonizing an abandoned building in New London, Connecticut. From the plants’ perspective, a decaying brick wall is just a limestone cliff. Courtesy Peter Tredici.

In Wild Urban Plants, Princess Tree (Paulownia tomentosa) is seen growing out the side of a neglected painted-brick building in New London, Connecticut. The caption informs us that, “From the plants’ perspective, a decaying brick wall is just a limestone cliff.” How marvelously enlightening!

The urban glacier leaves a trail of compacted glacial till in its wake. Courtesy Peter Del Tredici

Perhaps the most unique metaphor of all can be found in the picture of a  backhoe sitting atop a hill of dirt. The author tells us “The urban glacier [referring to the backhoe] leaves a trail of compacted glacial till in its wake.” A conglomerate of unsorted broken rocks, till does not provide amenable growing conditions for very many species of plants.

The author doesn’t go into this subject, but moss is often the first colonizing organism to move in. It secretes organic acids that break down the rocks into soil, paving the way for plants with the ability to fix nitrogen to come in, and over time, as plants die, the soil is enriched via their nitrogen, allowing other kinds of plants to live here. An understanding of this process is sorely lacking among those conservationists who insist that “invasive” plant species serve no useful purpose in the environment. In fact, it’s a darned good thing they are here, given their ability to flourish under present environmental conditions. This is the explanation, after all, for their apparent invasiveness.

Dr. Tredici’s “Introduction” should be required reading for everyone involved in conservation. With a better comprehension of how the natural world works, people should be able to realize that the United States is wasting many millions of taxpayer dollars every year to remove alien plants. And annually putting millions of pounds of herbicides into our environment (according to a 2012 Environmental Protection Agency report (3)) manifests a horrendous crime against nature.

This counterproductive war on nonnative plants must be stopped quickly; far too much damage has already been done. Spread the word about this book to everyone you know.

References:

  1. https://www.thefreedictionary.com/Plant+succession
  2. Bringing Nature Home, Doug Tallamy
  3. https://www.epa.gov/sites/production/files/2017-01/documents/pesticides-industry-sales-usage-2016_0.pdf

Observations of the Blue Ridge Naturalist

I’ve been a nature writer/photographer in Crozet, Virginia, for more than 25 years. My freelance articles have been published in numerous national and state magazines and newspapers, and I’ve written nature columns for many newspapers, as well as Virginia Wildlife, the magazine of our state wildlife department. My yard was featured on Virginia PBS stations in 1994 and again in 2005, and is the basis of my book, The Nature-friendly Garden: Creating a Backyard Haven for Plants, Wildlife, and People (Stackpole Books, 2006).  In all of these venues, I discussed nonnative plants, including some considered “invasive”, without suffering much, if indeed any, blowback.

Home of Marlene Condon in Crozet, Virginia. Photo credit Marlene Condon

However, over the past quarter century, there has been more-and-more of a push by native-plant societies to get government entities and environmental groups to rid the natural world of so-called invasive plants, including even native plants considered “thugs” because their growth is exuberant.  Because I was concerned about the destruction of habitat and the often-extensive use of pesticides to accomplish their mission, I started writing explicitly about this movement, as in the article below.

After the publication of this article last year, nativists mounted a smear campaign against me personally, a sure sign of how weak their invasive-plant arguments are.  The lead writer never even publicly disclosed her affiliation with the Blue Ridge PRISM, a group “targeting common invasive plants in the Blue Ridge”, which would have allowed readers to question whether her comments about me were suspect. My editor certainly was duped, placing a headline of “Blue Ridge Naturalist–NOT!” over their comments. And perhaps not coincidentally, shortly thereafter, he fired me, even though I’d written for–and received high praise from–him for 11 years.

Since then, I’ve found it virtually impossible to write openly about any nonnative plants.  Media and environmental groups are cowed by these people, thanks to their numbers and involvement with various organizations and governments (local, state, and federal). Sadly, this movement is highly detrimental to our natural world that is already in very bad shape and can hardly withstand yet more negative impacts upon it. Folks who understand the senselessness of destroying functioning habitat and poisoning the Earth with pesticides must speak out publicly for the benefit of nature.

Marlene Condon, Blue Ridge Naturalist

FEBRUARY 2019
The Blue Ridge Naturalist
© Marlene A. Condon

Bees and other kinds of insects obtain nourishment from the blooms of Weigela, a spring-blooming shrub native to Asia. Photo credit Marlene Condon

Ecologists Recognizing Value of Alien Plants

Scientists are either waking up to what I’ve been saying for years, or finally becoming brave enough to speak out against the wide-spread invasive-plant movement. In an opinion piece signed by 19 ecologists in the journal Nature, they argue that “policy and management decisions must take into account the positive effects of many invaders.”

Recognizing that “It is impractical to try to restore ecosystems to some ‘rightful’ historical state”, they go on to point out that eradicating or drastically reducing the abundance of invasive plants is “an impossible goal.”

Critical thinking is a must for deciding invasive-plant policy to avoid harming wildlife and wasting millions in tax dollars. A situation in California illustrates the foolishness of blindly pushing an agenda without giving any thought to the real-world consequences of doing so.

In the name of “saving” the environment from so-called invasive plants, a movement has sprung up to remove Eucalypt (Eucalyptus globulus) trees from California. These trees, brought in from Australia, now serve as the most frequented overwintering sites for the western Monarch butterfly population.

Monarchs originally roosted in native conifer stands of Monterey Pine (Pinus radiata), Monterey Cypress (Cupressus maculatum) and Coast Redwood (Sequoia sempervirens). Sadly, extensive development, logging, and poor land-management decisions have reduced the number of these native-tree stands, leaving the butterflies to rely upon non-native Eucalypts.

Ignoring the fact that overwintering Monarchs are very much dependent upon isolated stands of these trees, government plans are mandating removal of them. Does this make environmental sense? Absolutely not; eradication of the Eucalypts means no wintering habitat for Monarchs, which means they will die.

In other words, this deliberate destruction of habitat is taking place because of ideology, an illustration of the danger posed by people who have been led to believe they are part of an environmentally moral crusade. Native-plant folks out west have managed, as they have here in the East, to convince environmental organizations and government entities at every level that it is a moral imperative to remove plants deemed invasive.

But, the whole point of conservation of the environment is conservation of wildlife, without which the environment cannot function properly. Yet, absolutely no thought is given to how much so-called invasive plants support wildlife or serve important environmental functions in degraded areas.

Thus, for example, in the city of Waynesboro, Virginia, the Parks and Rec department decided it had to remove Japanese Knotweed (Fallopia japonica, formerly known as Polygonum cuspidatum) from growing along the South River greenway (Waynesboro News Virginian, March 9, 2018, “War on Weeds”). The main reason given for the removal of these plants was that they are preventing native plants from growing, but this statement is nothing more than invasive-plant folklore that gains credence by the act of repetition.

Read about virtually any “invasive” species and you will find that these plants are typically growing in disturbed areas where man or a weather event destroyed the original soil profile. As a result, the plants that had been growing there previously did not come back because they could not handle the altered physical conditions of the site. It’s why you see so-called invasive plants mainly along roadways, in parks, and along river trails—all areas easily seen by people who then mistakenly believe the exotic plants pushed out native species.

The newspaper stated that knotweed is a “formidable culprit to the river’s health”, but the true threat lies in its removal. This plant has superbly performed erosion control of soil in which native plants struggle to grow; feeds numerous kinds of pollinators when it blooms; and provides wonderful cover and nesting sites for numerous species of birds and the non-herbivorous insects that feed them. One need only to walk the trail with open eyes and an open mind to ascertain the truth of this statement.

Additionally, park employees would use herbicides to kill the knotweed. How can poisoning the Earth be less harmful than allowing alien plants to grow in areas where they are currently the most suited to thrive and thus provide badly needed habitat for wildlife?

You might wonder how the invasive-plant movement became so entrenched in environmental and governmental circles. The answer lies in the treatment of it as a moral cause in which those who agree with removing “bad” plants are virtuous; those who disagree must be bad like the plants themselves. Under these circumstances, it is difficult for folks to take a stand in opposition; no one wants to be considered immoral.

However, this undertaking is deeply flawed. Rather than critically analyzing each situation and dealing with it in the most appropriate manner, plant nativists (people who practice a policy of favoring native plants over nonnative) take the simplistic approach that demands removal of every plant designated as “invasive”, no matter what function it is fulfilling in the local environment or how well it fills what would be an otherwise empty ecological niche.

Earlier this year, for example, someone removed a Leatherleaf Mahonia (Mahonia bealei) that was growing in a swath of red dirt along the road where I exercise. It was one of the few plants that had survived the highway department’s installation of a new guardrail. No native plants had been able to grow in the poor, dry soil exposed a few years earlier by construction, leaving an area several feet wide and long mostly devoid of plants to assist wildlife.

The Mahonia (a native of China) would have provided a very early source of nectar desperately needed by the first pollinators to become active in spring at a time when native plants in bloom are very few. Its fruits would later feed birds, such as Cedar Waxwings and American Robins. Now, not much exists in this area to feed either insects or birds, making the land a wasted resource.

Native or not, plants provide habitat whereas bare ground does not. Nativists disregard the reality that native plants struggle to survive under the adverse conditions of road salt, mowing, drought, and disturbed, compacted, and depleted soil. They would do better by the environment if, instead of pulling and pesticiding, they focused on eliminating the actual causes of alien-plant spread.

Removing the Mahonia near the bridge resulted in no benefit to the environment, whereas it very much negatively impacted ease of survival for many insects and birds. And in California, removing Eucalypts may well doom the wintering Monarch butterfly population.

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

Baseless generalizations in Doug Tallamy’s Nature’s Best Hope

Doug Tallamy’s latest book, Nature’s Best Hope, continues his crusade against non-native plants.  He now calls invasive plants “ecological tumors.”  You might be tempted to respond that invasive plants are a small subset of non-native plants until you realize that Tallamy calls 3,300 plant species in North America “invasive.”  There are approximately 6,500 species of native plants in California, which reminds us that introduced plants are often a significant portion of our urban landscapes.  The title of Tallamy’s book is a misnomer.  Nature is not confined to native plants, as Tallamy wishes it to be.

Tallamy makes no meaningful distinction between “invasive” and “non-native.”  The classification of berry-producing non-native plants as “invasive” is a case in point.  Although Himalayan blackberries are invasive, most other berry-producing non-natives in California are not.  Cotoneaster, pyracantha, and holly are a few examples of berry-producing plants being eradicated in the Bay Area that are not inherently “invasive.”  They spread because birds eat the berries and deposit the seeds elsewhere.

Cedar Waxwings in crab apple tree. Wikimedia Commons

Eradicating berry-producing plants deprives birds of an important source of food.  If herbicides are used to kill the plant, the birds are also exposed to harmful chemicals, known to reduce reproductive success and cause other sub-lethal health issues in wildlife. In the case of Himalayan blackberries, they are frequently eaten by children and adults, who are then exposed to the herbicides used to kill the shrubs that are often widespread in our parks and open spaces.  San Francisco’s Recreation and Park Department sprayed blackberries in San Francisco’s parks and open spaces 23 times in 2019.

Tallamy and his nativist allies claim that native plants are beneficial to wildlife, especially birds.  How can they claim that eradicating berry-producing plants benefits birds?  They do so by claiming that native berries are more nutritious than non-native berries.  In particular, they claim that native berries contain more fat than sugar and that migrating birds require berries with high fat content.   Tallamy cites one study in support of that claim, a study that compared fat and sugar levels in the berries of 9 species of plants in the Northeast, 5 native species and 4 introduced species.  They found that the native species they analyzed had more fat content than the introduced species they analyzed. (1)

Generalizations unsupported by evidence

From that single study of nine plant species, Tallamy generalizes that berries of plants that are considered native in Asia are less nutritious for migrating birds than the berries of native plants in North America are. (None of the nine plant species studied occurs in California.)  Does that generalization make sense?

  • Tallamy does not provide any evidence that there are fewer migratory birds in Asia, or that the nutritional needs of migratory birds in Asia are different than those in North America. In fact, looking at the migratory patterns of birds confirms that migratory routes of birds span several continents.  The intercontinental flights of birds sometimes span both Asia and North America.  There is no logical or evidentiary explanation for berries of native plants in Asia being uniformly less nutritious than native plants in North America.
  • However, Tallamy offers evidence of the similarity between plants in Asia and closely related plants in North America. Wooly adelgids quickly made a transition to native hemlocks when they arrived in North America from Asia because its native host in Asia is closely related to the American native.  The adelgid has “all but eliminated hemlocks” in America, according to Tallamy.  The emerald ash borer has killed millions of ash trees in America when it arrived from Asia, where its native host was closely related.  On one hand, Tallamy claims that native plants in America are unique, completely different from plants in Asia, yet he recognizes that insects from Asia rapidly adapt to closely related host plants in America.
  • Asian species are not so foreign to America as Tallamy wishes us to believe. There are relicts of vegetation that extended completely around the Northern Hemisphere about 50 million years ago that were broken up by a combination of mountain-building and climate change. Tree of Heaven, Gingko, and Dawn Redwood, now considered introduced trees from Asia, occurred here naturally during that geologic period.  Tallamy says we must confine our choices to plants that “share an evolutionary history.”  In fact, many plants now considered non-native shared an evolutionary history with plants now considered native. Trees are time travelers, marching to the beat of the Earth’s geologic and climate drum.  Now they must be on the move to survive our changing climate.  We should not stand in their way.

Such generalizations unsupported by evidence are typical of Tallamy’s work.  In “Native plants improve breeding and foraging habitat for an insectivorous bird,” Tallamy and his collaborators conclude, “We demonstrate that residential yards dominated by nonnative plants have lower arthropod abundance…that function as population sinks for insectivorous birds.”  The data provided do not support such a broad generalization.  They studied one species of bird, in one geographic location, in a short period of time.  They inventoried arthropods for two years in a single month time-frame.  They quantify only one variable (plant foliage biomass) in addition to the nativity of plants, the abundance of insects, and the breeding success of one bird species.  They have not taken into consideration intervening variables such as variations in temperature, rainfall, pesticide use, etc.  The bird species studied is abundant within its range.  Its conservation status is “Least Concern.”  The abundance of this bird species does not justify the dire predictions of Tallamy’s study.

In conclusion

I have focused on just one of the many controversies discussed in Doug Tallamy’s new book.  I haven’t touched on the two most fundamental errors in Tallamy’s work:

  • Tallamy underestimates the speed of adaptation and evolution. There is ample evidence of rapid adaptation to non-native vegetation, including Tallamy’s examples of wooly adelgid and emerald ash borer making a quick transition to North American native trees after arriving from Asia.
  • He exaggerates the degree of specialization among insects. For example, he claims that 30% of native bees are “host-plant specialists,” yet Bees of the World (Michener, Johns Hopkins University) estimates a global average of 9% of bee species use plants within the same genus and it is “exceedingly rare” for bee species to be confined to only one plant species.

We have explored those issues in Tallamy’s work in previous articles:

  • Doug Tallamy claims that insects eat only native plants, yet his own study proves otherwise: HERE
  • Doug Tallamy claims that non-native plants are “ecological traps for birds.”  HERE is an article that disputes that theory.
  • Doug Tallamy claims that native and non-native plants in the same genus are not equally useful to wildlife, but he is wrong about that.  Story is HERE.
  • Doug Tallamy advocates for the eradication of butterfly bush (Buddleia) because it is not native.  He claims it is not useful to butterflies, but he is wrong about that.  Story is HERE.
  • Doug Tallamy publishes a laboratory study that he believes contradicts field studies, but he is wrong about that.  Story is HERE.
  • Doug Tallamy speaks to Smithsonian Magazine, Art Shapiro responds, Million Trees fills in the gaps:  HERE

(1) B. Smith, et. al., “The value of native and invasive fruit-bearing shrubs for migrating birds,” Northeastern Naturalist, 2013, 20(1): 171-84.