Author: Conservation Sense and Nonsense

California: A State of Change

Laura Cunningham’s book, A State of Change*  is a remarkable achievement, reflecting a lifetime of observing nature, informed by formal training in paleontology and biology and finally depicting that knowledge in oil paintings of the historical ecology of California. 

Ms. Cunningham introduces her theme with the title of her book.  California is the state that changes and is always in a state of change.  She acknowledges the physical forces of geology and climate as well as the biological interactions of plants and animals as she describes the dynamic qualities of nature.  She treats the complexity of these interactions with respect, frequently declining to reach conclusions because of the speculation that would be required to do so. 

Although we will touch on just a few themes of her book which are relevant to the mission of the Million Trees blog, we encourage readers to give this book the complete read it deserves. 

Sustainability of native plant gardens

Site of the El Cerrito Plaza with the Albany Hill in the background, centuries ago. Oil painting by Laura Cunningham, with permission

Ms. Cunningham tells the charming story of her first experience with native plant restorations as a teenager in the hills of Berkeley/Richmond in the mid-1980s.  With her parents’ permission, she dug up the lawn in their backyard so that she could plant native grassland.  She started with the seeds of native grasses that she collected locally and later transplanted native bunch grasses from nearby properties slated for development.  After several years of regular weeding and new planting, her small plot resembled the grassland she had envisioned.

When she finished her education at UC Berkeley and began to work further away, her grassland slowly succeeded to shrubs and non-native plants, a process she describes as follows: 

“Visiting deer brought weed seeds in on their fur, scrub jays planted live oak seeds into the grass, and flying finches dropped the seeds of Himalayan blackberry in the yard.  The latter, a thick, tenacious vine, slowly formed great thickets over the grasses, shading them out in places.  The food web had won, although I had learned a lot in the process.  I dug up the yard again, back to bare dirt, and gave it back to my parents.” 

This personal story is consistent with other local experiences reported on the Million Trees blog:

 Fire Ecology of California

Those who continue to believe that non-native plants are more flammable than native plants should read Ms. Cunningham’s book, which describes at length the important role that fire plays in California’s ecology.  She introduces this topic with the heading, “Chaparral:  Burning Like a Torch of Fat.”  Charcoal deposits in ancient sediments prove that wildfires in California’s brushlands have occurred frequently for hundreds of thousands of years.  Some shrubs, such as chamise, contain resinous leaves that encourage burning.  Others, such as ceanothus and manzanita require the intense heat of a fire to germinate.  Others will germinate only in the ashes of a fire.  As we have said repeatedly on the Million Trees blog, eradicating non-native plants and trees will not eliminate fire from California.

Ms. Cunningham also reports on the modern debate about reducing wildfires in California.  Although we are very familiar with this debate, we have not read so clear a presentation of it as Ms. Cunningham provides. 

One “camp” in this debate believes that the suppression of wildfires in California has resulted in fuel loads that are much greater than in the past and therefore result in bigger, more damaging fires.  This camp believes that fire danger can be reduced by allowing smaller fires to burn and conducting periodic prescribed burns. 

The opposing view is that fire suppression has been largely unsuccessful and therefore fuel loads are not substantially greater than they were historically.  Wildfires are attributed to hot, wind-driven fire in which fuel load is irrelevant; that is, everything will burn in a wind-driven fire.  Although this is the historical fire regime, fires are causing more loss of lives and property in modern times only because of the development of residential communities in the wildland-urban interface.  This camp therefore sees no point in prescribed burns and proposes to reduce risk to lives and property by limiting residential developments in wildlands and creating defensible space around residences by eliminating most vegetation. 

With humility, Ms. Cunningham declines to choose a side in this debate, acknowledging there is much compelling evidence to support both views. 

The Million Trees blog prefers the theory that wildfires are caused by hot winds rather than accumulated fuel loads because our perspective is limited to the San Francisco Bay Area.  We don’t think prescribed burns are appropriate in a densely populated urban setting where both pollution and risk of wildfire are major concerns.  And, based on our local experience, the only fires that have become raging wildfires are those that were wind-driven.   We advocate for reducing fire hazards by creating defensible space and routine maintenance of flammable vegetation litter.   

Historical Ecology

San Francisco 500 years ago, looking eastward from the top of Nob Hill. Oil painting by Laura Cunningham, with permission

We are grateful to Ms. Cunningham for giving us permission to publish two of her historical paintings of California.  These paintings enable us to confirm that trees were not a conspicuous part of the landscape of the Bay Area.  The dominant landscape was grassland and shrubs.  Although there may have been more trees if the landscape had not been frequently burned by Native Americans, based on our knowledge of horticultural requirements of native trees, we believe that even in the absence of fire there would have been few trees.  The native trees will not tolerate the wind on the hills of San Francisco.  Even in places where trees are sheltered from the wind, they must have access to sufficient water to become established. 

When native plant advocates demand that non-native trees be destroyed, they frequently claim that non-native trees will be replaced by native trees (even without being planted in some cases).  We assume their claims are based either on strategy (i.e., promising “replacement” trees in order to diffuse the opposition of those who like trees) or on ignorance of California’s natural history. 

With deep respect, we acknowledge Ms. Cunningham’s impressive knowledge of California’s ecological history and the accomplishment which her book represents.  Our thanks to Ms. Cunningham for sharing her lifetime of study and observation of nature with us and rendering that knowledge so beautifully in her paintings. 

* Cunningham, Laura, A State of Change:  Forgotten Landscapes of California, Heydey Books, Berkeley, California, 2010

Cultural Lag: Public policy lags behind science regarding “invasion biology”

This is a good-news-bad-news story.  The good news is that the most successful environmental organization devoted to the preservation and conservation of wildlands, The Nature Conservancy, has announced its intention to reorder its priorities in what we hope will be a less destructive direction.  The Conservancy is a science-based environmental organization that is unique in that regard.  It employs over 600 scientists to guide and inform its projects, in contrast to many other organizations that employ more lawyers than scientists.  The scientific orientation of the Conservancy undoubtedly puts it in a position to reflect and respond to the increasingly loud voices of other scientists who are expressing concern about the costs and environmental damage that are the unintended consequences of the “restorations” which have evolved out of invasion biology.

The bad news is that public policy regarding native plant “restorations” lags far behind the developing scientific consensus regarding invasion biology, namely that original theories require revision.  This is the consequence of the cultural lag that is inevitable when science moves forward, but communication of its findings to the general public lags behind. 

The Nature Conservancy redefines its goals

In the past few months, the Chief Scientist of the Nature Conservancy, Peter Kareiva, has written several articles in the Conservancy’s publications expressing his views about the future of conservation.  In “Beyond Man vs Nature,”(1) Kareiva is quoted as saying that species preservation should not be the top priority of the Conservancy.  He admits he is “not a biodiversity guy.”  Rather, he says, “The ultimate goal [should] be better management of nature for human beings.”  He does not agree with those who claim that the earth is fragile and man must be excluded from nature in order to protect it.  He considers nature resilient.  He calls the concept of “biodiversity hot spots” sham science and he rejects the notion that conservation and development are mutually exclusive.  We wants conservation efforts to focus on the things that people need from nature such as clean water and clean air.  If and when people experience the benefits of conservation, they will support and participate in those efforts.  The Conservancy can’t save the world alone.  The active participation of the human population is required to achieve the Conservancy’s conservation goals. 

Golden Gate Park San Francisco. Most plants and trees in GG Park are not native. Creative Commons Attribution - Share Alike

In “Conservation should be a walk in the park, not just in the woods,”(2) Kareiva says that the Conservancy should participate in more urban conservation projects because that’s where most people live and even more will live in the future.  He wants conservation to be more visible to people and he wants people to benefit directly from the projects.

In his most recent publication, “Invasive Species:  Guilty until proven innocent?” Kareiva acknowledges the debate about invasive species.  On the one hand, a few invasive species have done a great deal of harm, particularly on islands.  On the other hand, many invasive species aren’t doing any harm and some are benefitting native species, even endangered species in some cases (e.g., Southwestern Willow Flycatcher in Tamarisk).  He concludes, “Science-based conservation cannot be about knee-jerk platitudes and simple views of good and evil…the fact is we cannot control all invasive species, and in many cases, yesterday’s invaders have become plants and animals that are beloved by local people.” 

There is nothing scientifically new to us in what Kareiva has said recently.  What’s new is that he speaks as a representative of one of the most important environmental organizations in the world.  Therefore, he makes a connection between scientific theory and action.  That is new….very, very, new and very encouraging.

Public policy always lags behind science

Public policy is inherently conservative.  It usually reflects consensus and consensus occurs late in every scientific debate.  Once that consensus is finally reached, changing it is a slow process.  And so, we are not surprised by the most recent example of a local community continuing the crusade to eradicate non-native trees.  Two ordinances were recently passed in the Los Altos Hills on the San Francisco peninsula, to do just that. 

  • Citizens building or expanding buildings on their properties will be required by ordinance 10-2.802 to cut down all eucalypts within 150 feet of any roadway or structure.
  • “Town guidelines concerning restoration action” (5-8.08) “deems certain trees undesirable,” including Monterey pine and cypress, as well as eucalyptus.

We are heartened by the publication which announces these new policies.  The author objects to being dictated to regarding her tree preferences.   She also responds to the usual myths regarding the negative qualities of eucalyptus.  In response to the usual justification for its eradication, that it is not native, the author says, “Who cares?”  Indeed, who cares?  We certainly don’t care and we speculate that the vast majority of people in Los Altos Hills don’t care either.  When we speak up on behalf of our trees, we speed the process of changing public policy to reflect the considerable scientific evidence that non-native trees are not harming anything or anyone.   Indeed, their eradication is causing far more harm to the environment by releasing tons of sequestered carbon and requiring greater herbicide use.    

(1) Nature Conservancy, Spring 2011

(2) Nature Conservancy, Issue 2, 2011

Fortress Conservation: The loss of recreational access

Sharp Park, Pacifica, CA. Photo by Erica Reder, SF Public Press

The recent publication of an article about Sharp Park in Pacifica, featuring a photo of this sign has inspired us to consider the recreational access restrictions that often accompany native plant and animal conservation projects.

In this case, an 18-hole golf course in Sharp Park is at stake.  A coalition of environmental organizations (1) recently sued the City of San Francisco to close this golf course, based on their claim that the golf course violates the Endangered Species Act by harming two endangered species (Red-legged frog and San Francisco garter snake).  The City of San Francisco claims that the golf course can be reconfigured to accommodate these species.  Meanwhile, conservation efforts requiring closure of recreational areas, according to this sign, are continuing.

The organizations that have sued San Francisco also claim that the closures they demand will actually improve recreational opportunities.  This claim is based on an assumption that the preferred form of “recreation” is standing on a trail or boardwalk behind a fence, looking at wildlife through binoculars.  Naturally, people who play golf see it otherwise.

We don’t claim to know the needs of these particular endangered species.  However, based on similar claims in other parks, we are skeptical.  In our experience, environmentalists—and sometimes park managers—often claim that animals are more fragile than scientific evidence or actual experience suggests.  We therefore suspect that animals are sometimes used by environmentalists and park managers to justify closing recreational areas. 

Loss of recreational access at Fort Funston, San Francisco

In a series of closures from 1997 to 2000, the Golden Gate National Recreation Area (GGNRA) fenced visitors out of more than 28 acres of Fort Funston (about 15% of total acreage), claiming the land was “bank swallow habitat” and that the swallows needed the closures for protection of their breeding colony.  In fact, the fenced land is not bank swallow habitat.  The swallows do not nest, breed, feed, roost, or do any of the normal activities a bird does in its habitat, inside the closures.  The swallows fly over it on their way from their nests on the cliff face above the beach to Lake Merced where they feed on insects.  The GGNRA sponsored a study(2) of wildlife in the fenced areas during the breeding season of the swallows, when the swallows were present.  The study included a census of all birds observed inside the enclosure and reported not a single bank swallow.

A swallow expert, William M. Shields, SUNY Professor of Biology, said of the closures, “I do not believe that a closure of the size and type described by the park service is required or even would benefit the Bank Swallow at all.”  He said that the closure was based on “…their [GGNRA’s] misrepresentations about the needs and safety of the Bank Swallows breeding in the cliffs.”  Dr. Shields classified GGNRA’s claims of providing improved feeding habitat as, “…a major stretch and smacks of special pleading to me.”

Bank swallow burrows (circled) in cliff above beach at Fort Funston

The bank swallows nest in burrows in the cliff faces at Fort Funston, where they are out of reach of recreational visitors who seldom even notice the presence of the birds.  Furthermore, as Dr. Shields notes, “The Bank Swallow like other swallows is quite suited to live with humans and their pets.”  Another swallow expert, Barrett Garrison says in his monograph Bank Swallow, “Bank Swallows appear relatively insensitive to moderate levels of human-induced disturbance.”  Garrison lists documented land uses around Bank Swallow colonies:  hydroelectric power generation, irrigation, recreational boating, commercial agriculture, vehicular and pedestrian traffic, and livestock grazing.

Bank swallow nests in……
…a sheep pasture

When the public was fenced out of large areas of Fort Funston, the bank swallow was just a phony excuse.  We try to avoid speculating about the motivation of others, but in this case the massive native plant “restoration” that followed the closure seems the likely goal of the closure. 

Loss of recreational access at Albany Bulb in the East Bay

Frenced enclosure at Albany Plateau for theoretical burrowing owls

In 2008, 8 acres of the Albany Plateau (the flat area at the east end of the Albany Bulb) was fenced at a cost of $125,700.  The stated purpose of this fenced enclosure was to create habitat for the burrowing owl, although owls had never been seen nesting there.  Three years later there are still no burrowing owls in this fenced enclosure.  In fact, there is nothing in this fenced area and nothing is happening there.  Update:  Ten years later, no owls have been seen nesting there.  November 2017

How did we lose this recreational resource?  That is a fascinating story:  “During the planning process for the Eastshore State Park…the demonstration of community need for sports fields led to the designation of the eastern side of the Albany Plateau as “active recreation” land use category.  This was problematic because of its proximity to the Albany Mudflats State Sanctuary and because State Parks is not in the practice of operating formal sports fields facilities.”(3)  Consequently, the Tom Bates Regional Sports Complex south of Golden Gate Fields was approved for development as sports fields.  Unfortunately one burrowing owl had been seen (but was not nesting) in that area two years before.  Therefore, environmentalists demanded “mitigation” for the development of a sports field in that area.  The “mitigation” was the creation of the 8-acre fenced enclosure on the Albany Plateau.  So far, burrowing owls have not elected to use the fenced area.

But why would a burrowing owl choose to nest on the Albany Plateau when it has a nesting area just a few miles down the road at the Cesar Chavez Park?  Burrowing owls can be seen nesting at Cesar Chavez Park every year from October to April.  There are post-and-rope fences that designate their nesting area, but those fences are not impenetrable as is the chain link fence on the Albany Plateau.  People (often with their dogs on leash) walk on trails within 20 feet of the owls.  The owls don’t seem disturbed by this activity and apparently prefer the busy Cesar Chavez Park to the fenced Albany Plateau.

Burrowing owl, Cesar Chavez Park, Berkeley

Are animals being used as tools to restrict recreational access?

We wish the animals could speak for themselves.  Do they require the enclosures that environmentalists demand for them?  We think the answer to that question is sometimes “NO!”  And when environmentalists make these claims repeatedly, do they lose their credibility when the evidence indicates that such restrictions are in fact not needed?  In other words, are environmentalists crying wolf?  Or do they accomplish their true goals by successfully fencing people out of our parks?  Is their goal an example of Fortress Conservation or a sincere effort to protect animals from harm?  Do park managers prefer parks without people?

(1) Wild Equity Institute, Sierra Club, Audubon Society, National Parks Conservation Association, Center for Biological Diversity

(2) “Evaluating Wildlife Response to Coastal Dune Habitat Restoration in San Francisco, California” by Will Russell, Jennifer Shulzitski and Asha Setty, Ecological Restoration, Vol. 27, No. 4, 2009

(3) City of Albany City Council Agenda Staff Report

Facts about carbon storage in grasses do not support assumptions of native plant advocates

We have received many comments from native plant advocates regarding carbon storage.  These comments defend projects in the Bay Area to destroy non-native forests and “restore” native plants by claiming that native plants will actually sequester more carbon than the forest that they propose to destroy.  As always, we are grateful for comments that give us the opportunity to research the issues and report what we have learned about this complex and important subject.

Carbon cycling in a terrestrial plant-soil system

The storage of carbon in plants and soil occurs as plants and soil exchange carbon dioxide (CO₂) with the atmosphere as a part of natural processes, as shown in the following diagram (1):

Green Arrow:  CO₂ uptake by plants through photosynthesis

Orange Arrows:  Incorporation of Carbon into biomass and Carbon inputs into soil from death of plant parts

Yellow Arrows:  Carbon returns to the atmosphere through plant respiration and decomposition of litter and soil Carbon.  Carbon in plant tissues ultimately returns to atmosphere during combustion or eventual decomposition.

Rates of carbon uptake and emissions are influenced by many factors, but most factors are related to temperature and precipitation:

  • Higher temperatures are associated with faster plant growth, which accelerates photosynthesis and carbon uptake.
  • Higher temperatures also accelerate decomposition of plant materials, thereby accelerating the return of stored carbon into the atmosphere.
  • The effect of moisture in the soil on decomposition can be graphed as a “hump.”  In extremely dry soils, decomposition is slow because the organisms that decompose vegetation are under desiccation stress.  Conditions for decomposition improve as moisture in the soil increases until the soil is very wet when lack of oxygen in the soil impedes decomposition.

Although temperature and precipitation are important factors in carbon storage, they don’t change appreciably when one type of vegetation is replaced with another.  Therefore, these factors aren’t helpful in addressing the fundamental question we are considering in this post, which is “Does native vegetation store more carbon than the forests that presently occupy the land in question?”

Where is carbon stored?

Source: U.S. EPA, 2018

Much of the carbon stored in the forest is in the soil.  It is therefore important to our analysis to determine if carbon stored in the soil in native vegetation is greater than that stored in non-native forests.  The answer to that question is definitely NO!  The carbon stored in the soil of native vegetation in Oakland, California is a fraction (5.7 kilograms of carbon per square meter of soil) of the carbon stored in residential soil (14.4 kilograms in per square meter of soil). (9)  Residential soil is defined by this study as “residential grass, park use and grass, and clean fill.”  This study (9) reports that the amount of carbon stored in the soil in Oakland is greater after urbanization than prior to urbanization because Oakland’s “wildland cover” is associated with “low SOC [soil organic carbon] densities characteristic of native soils in the region.”

Native plant advocates have also argued that the carbon stored in the soil of perennial native grasslands is greater than non-native trees because their roots are deeper.  In fact, studies consistently inform us that most carbon is found in the top 10 centimeters of soil and almost none is found beyond a meter (100 centimeters) deep. (1, 4) In any case, we do not assume that the roots of perennial grasses are longer than the roots of a large tree.

Another argument that native plant advocates use to support their claim that native perennial grasslands store more carbon in the soil than non-native trees is that native grasses are long-lived and continue to add carbon to the soil throughout their lives.  In fact, carbon stored in the soil reaches a steady state, i.e., it is not capable of storing additional carbon once it has reached its maximum capacity. (1)

It is pointless to theorize about why grassland soils should store more carbon than forest soils.  The fact is they don’t.  In all regions of the United States forest soils store more carbon than either grassland or shrubland soils.  (9, Table 5)

We should also describe Oakland’s native vegetation before moving on:  “Vegetation before urbanization in Oakland was dominated by grass, shrub, and marshlands that occupied approximately 98% of the area.  Trees in riparian woodlands covered approximately 1.1% of Oakland’s preurbanized lands…”  (5)  In other words, native vegetation in Oakland is composed of shrub and grassland.  When non-native forests are destroyed, they will not be replaced by native trees, especially in view of the fact that replanting is not planned for any of the “restoration” projects in the East Bay.

The total amount of carbon stored within the plant or tree is proportional to its biomass, both above ground (trunk, foliage, leaf litter, etc.) and below ground (roots).  Since the grass and shrubs that are native to the Bay Area are a small fraction of the size of any tree, the carbon stored within native plants will not be as great as that stored in the trees that are being destroyed.

Whether we consider the carbon stored in soil or within the plant, the non-native forest contains more carbon than the shrub and grassland that is native to the Bay Area.

Converting forests to grassland

If we were starting with bare ground, it might be relevant to compare carbon sequestration in various types of vegetation, but we’re not.  We’re talking about specific projects which will require the destruction of millions of non-native trees.  Therefore, we must consider the loss of carbon associated with destroying those trees.  It doesn’t matter what is planted after the destruction of those trees, nothing will compensate for that loss because of how the trees will be disposed of.

The fate of the wood in trees that are destroyed determines how much carbon is released into the atmosphere.  For example, if the wood is used to build houses the loss of carbon is less than if the wood is allowed to decompose on the forest floor.  And that is exactly what all the projects we are discussing propose to do:  chip the wood from the trees and distribute it on the forest floor, also known as “mulching.”  As the wood decomposes, the carbon stored in the wood is released into the atmosphere:  “Two common tree disposal/utilization scenarios were modeled:  1) mulching and 2) landfill.  Although no mulch decomposition studies could be found, studies on decomposition of tree roots and twigs reveal that 50% of the carbon is lost within the first 3 years.  The remaining carbon is estimated to be lost within 20 years of mulching.  Belowground biomass was modeled to decompose at the same rate as mulch regardless of how the aboveground biomass was disposed” (8)

Furthermore, the process of removing trees releases stored carbon into the atmosphere, regardless of the fate of the destroyed trees:  “Even in forests harvested for long-term storage wood, more than 50% of the harvested biomass is released to the atmosphere in a short period after harvest.”  (1)

Will thinning trees result in greater carbon storage?

Native plant advocates claim that thinning the non-native forest will result in improved forest health and therefore greater carbon storage.  In fact, the more open canopy of an urban forest with less tree density results in greater growth rates.  (3)  Although more rapid growth is associated with greater rates of carbon sequestration, rates of storage have little effect on the net carbon storage over the life of the tree.  (6)  Net carbon storage over the life of the tree is determined by how long the species lives and how big the tree is at maturity.  These characteristics are inherent in the species of tree and are little influenced by forest management practices such as thinning. (6)

More importantly, even if there were some small increase in carbon storage of individual trees associated with thinning, this increase would be swamped by the fact that over 90% of the urban forest will be destroyed by the proposed projects we are evaluating in the East Bay.  The projects of UC Berkeley and the City of Oakland propose to destroy all non-native trees in the project areas.  The project of the East Bay Regional Park District proposes to destroy all non-native trees in some areas and thin in other areas from 25 to 35 feet between each tree, reducing tree density per acre by at least 90%.  No amount of “forest health” will compensate for the loss of carbon of that magnitude.   

Responding to native plant advocates

  • The vegetation that is native to the Bay Area does not store more carbon above or below the ground than the non-native forest.
  • Chipping the trees that are destroyed and distributing the chips on the ground will not prevent the release of carbon from the trees that are destroyed.
  • Thinning the trees in our public lands will not increase the capacity of the trees that remain to store carbon.

 ————————————————————————————————–

Bibliography

  1.  Anderson, J., et. al., “The Potential for Terrestrial Carbon Sequestration in Minnesota, A Report to the Department of Natural Resources from the Minnesota Terrestrial Carbon Sequestration Initiative, February 2008.
  2. Birdsey, Richard, “Carbon storage and accumulation in United States Forest Ecosystems,” USDA Forest Service, General Technical Report WO-59, 1992
  3. Environmental Protection Agency, “Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2008,” April 15, 2010., EPA 430-R-10-006
  4. Fissore, C.,  et.al., “Limited potential for terrestrial carbon sequestration to offset fossil-fuel emissions in the upper Midwestern US,” Frontiers in Ecology and the Environment, 2009, 10.1890/090059
  5. Nowak, David, “Historical vegetation change in Oakland and its implication for urban forest management,” Journal of Arboriculture, 19(5): September 1993
  6. Nowak, David, “Atmospheric Carbon Reduction by Urban Trees,” Journal of Environmental Management, (1993) 37, 207-217
  7. Nowak, David. Crane, Daniel, “Carbon storage and sequestration by urban trees in the U.S.A.,” Environmental Pollution, 116 (2002) 381-389
  8. Nowak, David, et.al., “Effects of urban tree management and species selection on atmospheric carbon dioxide,” Journal of Arboriculture 28(3) May 2002
  9. Pouyat, R.V. (US Forest Service)., et.al., “Carbon Storage by Urban Soils in the United States,” Journal of Environmental Quality, 35:1566-1575 (2006)

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

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

  •  Its dense growth provides protection against storm surge and “erosion control along shorelines, canal banks, levees, and other areas of soil-water interface.”(1)
  • It filters nutrients, sediments and toxins from the water that flows off the land before reaching the ocean, acting as a natural water treatment facility.
  • It provides cover and food for birds, mammals and marine animals that live in the coastal marsh.  Many other marsh plants occupy the same marshlands.

    Spartina alterniflora, Smooth Cordgrass. USDA photo

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

  • In 2001 the Governor of Louisiana declared a “state of emergency” when Smooth Cordgrass declined and the state obtained $3 million of federal funding to study and hopefully reverse the decline.  This study resulted in the development of a method of aerial seeding of Smooth Cordgrass to restore declining areas of marshland.(2)
  • A similar, but smaller dieback of Smooth Cordgrass in Georgia led to a collaborative research and on-going monitoring effort by 6 research institutions in Georgia.(3)
  • Similar dieback of Smooth Cordgrass has been reported as far north as the coast of Maine.  A researcher at the Connecticut Agricultural Experiment Station is quoted in that report as saying, “In New Orleans, if their marshes were intact, the storm surge of Katrina would not have reached the levees.”(4)

The war on Smooth Cordgrass in the West Coast 

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

  • $24 million was spent to eradicate Smooth Cordgrass in San Francisco and Willapa Bay from 2000 to 2010 (5)
  • $16.3 million is projected to be spent on eradication efforts on the entire West Coast from 2011 to 2020 (6)

In 2006, 2,000 acres were treated with herbicides to eradicate Smooth Cordgrass in the San Francisco Estuary.    Most were retreated 3 to 5 times after initial treatment.  In 2010, twenty five sites were slated for retreatment, usually with herbicides.  The San Francisco Estuary Invasive Spartina Project (ISP) “defines a need for a zero tolerance threshold on invasive Spartina in the San Francisco Bay.”(7)

The ISP reports that imazapyr (Habitat) will be used in most sites, although it will sometimes be mixed with glyphosate (Roundup). (See SaveSutro for more information about imazapyr and its use in San Francisco.)  The ISP acknowledges that:

  •  “little is known about the interactive effects” of combining these herbicides or any of the surfactants used with these herbicides.
  • These herbicides will be applied using a variety of methods, including aerial spraying by helicopter.
  • Although the ISP considers imazapyr a relatively non-toxic herbicide, it also acknowledges that imazapyr has only been used since 2005.  Therefore, “Only few toxicity studies exist for birds…no data exist for the potential toxicity of imazapyr to shorebirds.”(8) Given that one of the stated purposes of eradicating Smooth Cordgrass is to benefit the endangered Clapper Rail, it seems surprising that nothing is known about the effects of imazapyr on any shorebird, including the Clapper Rail.

Why is Smooth Cordgrass treasured on the East Coast and reviled on the West Coast?  That question was asked and answered by Professor James Morris at an Environmental Law Conference in Eugene, Oregon on March 5, 2011.  Professor Morris studies Smooth Cordgrass at the Baruch Institute for Marine & Coastal Sciences at the University of South Carolina.  We urge our readers to watch a video of his presentation to the conference in Oregon.  We will draw upon that video in addressing the claims (9) made by those who are attempting to eradicate Smooth Cordgrass on the West Coast:

Indictment:  Smooth Cordgrass will invade mud flats, eliminating valuable habitat for plants and animals that inhabit that segment of marshland.

Defense:  According to Professor Morris, Smooth Cordgrass was introduced to the West Coast in shipments of Eastern oysters over 100 years ago without eliminating mudflats.  Europe has had similar experience with Smooth Cordgrass which was introduced there to reduce sediment in harbors.  Professor Morris showed pictures of Danish and Dutch estuaries in which Smooth Cordgrass has existed since the 1930s without radically altering the composition of the marshland.

Indictment:  Smooth Cordgrass will invade waterways, making them impassable.

Defense:  Again, since this has not happened in 100 years, there is no reason to assume it will happen in the future.  Furthermore, the USDA describes the narrow range of Smooth Cordgrass:  “the width and thickness of vegetative colonies are controlled by a number of site specific conditions such as elevation, shoreline slope, and frequency, depth and duration of flooding” as well as salinity and acidity.  In other words, the range of Smooth Cordgrass is limited.

Indictment:  Smooth Cordgrass does not provide habitat value equal to the native species of cordgrass with which Smooth Cordgrass competes, particularly for the endangered Clapper Rail.

Defense:  Mike Casazza at the Dixon Field Station of the USGS is presently studying the effect of eradicating Smooth Cordgrass on the reproductive success of the Clapper Rail:  “Removal of invasive Spartina accomplishes the goal of Spartina eradication, but if rails fail to survive and reproduce, then the goal of species protection is unfulfilled…the potential for impact from invasive Spartina removal and the potential for mitigation by rail ecology and behavior remain poorly understood.”(10)  Clapper Rails live in Smooth Cordgrass on the East Coast:  “numerous” Clapper Rail families were observed nesting in Smooth Cordgrass on Dewees Island, South Carolina.(11)

Indictment:  Smooth Cordgrass is outcompeting the native Pacific Cordgrass (Spartina foliosa) by displacement and hybridization.

Defense:  This is probably true because of the characteristics of the Pacific Cordgrass:  “S. foliosa occupies a very limited range in the intertidal zone, and the leaves and stems wither in fall and shed in the winter, leaving sparse standing matter that is ineffective at trapping sediment.  Seedlings of S. foliosa are seldom found in established marshes and appear only intermittently in sheltered upper mudflats.”(12)  In other words, the range of the native cordgrass is narrower, it does not grow as densely, and it is not foliated year around, thereby creating opportunities for the non-native cordgrass to occupy bare ground.  Since marsh grasses are beneficial to the environment and its inhabitants, the ability of Smooth Cordgrass to occupy this vacuum seems a benefit, particularly since native cordgrass is less capable of removing sediments from water, reducing its effectiveness as a filter of pollutants from water flowing into the bay.(13)

Smooth Cordgrass is treasured on the East and Gulf Coasts because it performs valuable ecology services.  Although it performs the same ecological functions on the West Coast, it is being eradicated.  The evidence available to us suggests that we are spending a lot of money and effort, as well as using a lot of herbicides, to eradicate Smooth Cordgrass only because it is not native to the West Coast.   

  • Smooth Cordgrass provides superior storm surge protection particularly during winter months when native cordgrass is dormant.
  • Smooth Cordgrass is more capable of filtering pollutants from water flowing into the bay.
  • Smooth Cordgrass provides at least equal habitat quality to the endangered Clapper Rail and probably other marsh plants and animals as well.
  • Smooth Cordgrass has not blocked waterways or eliminated mud flats in comparable situations over long periods of time

We invite our readers to supply us with evidence that there are legitimate reasons for the campaign against Smooth Cordgrass.

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

(3) Ibid.

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

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

(6) Ibid., page 6

(7) “San Francisco Estuary Invasive Spartina Project, 2010 Pesticide Application Plan,” page 15.

(8) Ibid. page 31

(9) “West Coast Governor’s Agreement on Ocean Health,” May 2010

(10) “Ecology of California Clapper Rail in the San Francisco Bay/Delta Region,” USGS Western Ecological Research Center

(11) Judy Drew Fairchild, “Watch for Clapper Rails and chicks,” Dewees Island, SC

(12)“West Coast Governors’ Agreement on Ocean Health,” May 2010, page 12

(13) “San Francisco Estuary Invasive  Spartina Project, 2010 Pesticide Application Plan,” page 10

Basing our opinion of eucalypts on experience rather than rumors

We received a comment from a reader in Wales that prompted us to visit her website, Clegyr  Boia.  She tells a story that contains an important lesson for us:   to observe the performance of plants in our gardens and to base our evaluation of them on actual experience rather than preconceived judgments.

Eucalyptus leucoxylon ‘Rosea’ Wikimedia Commons Jean Tosti

In retelling this story, we shall call the owner of Clegyr Boia by the location of her property.  Clegyr Boia’s favorable opinion of eucalyptus trees is based on her visit to Australia in 1980.  As we did, she could see the beauty of the eucalyptus forest in Australia.

When she bought her property in Wales, she viewed it as an opportunity to develop an artistically beautiful landscape that she knew would include eucalyptus trees.  She planted eucalypts around one of her art installations because the blue color and graceful curves of their leaves enhanced her rock sculptures.  She planted other species of eucalypts in areas of the garden to shield them against the wind.

Soon after she began to plant eucalypts on her property, she was visited by friends and neighbors who were concerned about the introduction of eucalypts to their area.  They warned against the invasive properties of eucalyptus.  They claimed that nothing would grow under the eucalypts and that they would not provide food for wildlife.

Clegyr Boia’s initial response was to remove the eucalypts she had planted.  Then she had second thoughts.  She realized that her garden was full of non-native plants that were thriving and were providing valuable food for the denizens of her home, including her.  Since much of the food we eat is non-native, she decided that nativity is not a suitable criterion for banning a plant from her garden.  She decided to observe the eucalypts closely and decide based on their actual performance in her garden if they needed to be removed.

Some years later, she considers the eucalypts in her garden important contributors to its beauty.  They have demonstrated that other plants are welcome in the shelter of their canopy and that insects make good use of them.  They have also been remarkably resilient in salty, windy conditions.  When they have died back after heavy storms, they have soon resprouted.   Everything in her garden must make its own way, including the eucalypts, thereby proving their sustainability in this harsh setting. 

Native blackthorn grows next to eucalyptus. Photo courtesy Clergy Boia

We invite our readers to visit the Clegyr Boia website for the complete story, as well as a historical review of the migration of eucalypts all over the world and speculation about why they have acquired a negative reputation.

We tell this story because we admire Clegyr Boia’s commitment to her trees.  She listened to her neighbors, but she also made the commitment to her trees to watch their behavior in her garden.  She based her ultimate judgment of their suitability on their actual performance in her garden.  They have rewarded her patience with their success.

A dialogue about insects and non-native plants

We received a comment on our “Wildlife” page from “entomologist” that deserves a comprehensive response. 

 Conversation with “entomologist”

 “entomologist:”  “Adaptation to exotic species by specialist herbivores is unusual.  Those butterflies that switch to exotics tend to be generalists already.”  

Webmaster:  “Entomologist” is mistaken that the butterflies now using non-native plants are generalists, by which we assume he means that they use many plants, rather than a specific species.  According to Professor Art Shapiro (UC Davis), 26 of the 82 species of California butterflies now feeding on exotic plant species, are using only one plant species.  In other words, nearly one-third of California butterflies presently using exotic plant species are not generalists.(1)  When butterflies have made the transition from a native to a non-native plant, the plants are usually chemically similar. 

Anise Swallowtail, Sutro Forest
Anise Swallowtail, Sutro Forest, March 2010

The Anise Swallowtail is a conspicuous example of a California butterfly that is now dependent upon a particular exotic plant, fennel. This relationship between a specific native insect and a specific non-native plant is one of the reasons why the Million Trees blog was created.  Non-native fennel is being eradicated by every native plant “restoration” in the Bay Area.   

Over ten years ago, a park advocate in San Francisco became enraged by the eradication of fennel in his park because he was aware of the dependence of the Anise Swallowtail upon the fennel.  He made every effort to convince the so-called Natural Areas Program to stop destroying the fennel in his park.  He enlisted the help of Professor Art Shapiro in that effort. His efforts were ultimately unsuccessful.  The Natural Areas Program considered the non-native origins of the fennel sufficient reason to eradicate it, regardless of the needs of a native butterfly.  They continue those eradication efforts to this day. 

It is such mindless destruction of non-native plants, regardless of their benefit to fauna (or other benefits) that has made the Natural Areas Program so unpopular with people with a broader view of nature. We value the Anise Swallowtail butterfly as much as any theoretical benefit from eradicating a non-native plant.

“entomologist:”  “This idea that exotic plants are as good for wildlife as natives is just plain pathetic, especially for anyone who knows about herbivory  patterns on native and exotic plants.”

Webmaster:  By “pathetic” we assume “entomologist” means that he does not believe that insects eat non-native plants.  He is mistaken that insects do not eat non-native plants.  Returning to Professor Shapiro, he reports that 82 of 236 (35%) total species of California butterflies feed on non-native plants. 

Professor Dov Sax (Brown University) compared insects living in the leaf litter of the non-native eucalyptus forest with those living in the native oak-bay woodland in Berkeley, California.  He found significantly more species of insects in the leaf litter of the eucalyptus forest in the spring and equal numbers in the fall.(2)  Professor Sax also reports the results of many similar studies all over the world that reach the same conclusion.

The California Academy of Sciences finds that several years after planting its roof with native plants, it is now dominated by non-native species of plants in the two quadrants that are not being weeded, replanted and reseeded with natives.  Their monitoring project recently reported that there were an equal number of insects found in the quadrants dominated by native plants and those dominated by non-native plants. 

Damselflies (probably Common Blue) mating on non-native ivy in Glen Canyon Park.

We also use our eyes when we walk in our parks.  We often find insects in non-native plants.  Those non-native plants are often targets for eradication.  The damselflies in a San Francisco park are another example of the contradictory strategies of the Natural Areas Program.  They have made several attempts to reintroduce the rare Forktailed Damselfly to one of the parks in San Francisco.  Although those attempts have not been successful, we see other species of damselflies in that park, using the non-native plants that are repeatedly sprayed with herbicides by the Natural Areas Program.  We wonder if the herbicide use in that park is contributing to the failure of attempts to reintroduce the Forktailed Damselfly. Does the right hand know what the left hand is doing?

“entomologist:”  “Insects eating plants are at the base of the food chain and native plants have more insect herbivores and support more native birds.”

Webmaster:  We can agree that many birds eat insects and those that do are likely to benefit from greater populations of insects.  But, there is substantial evidence that insects are as likely to be found in non-native plants as in native plants and we trust that the birds know where to find them.  However, unlike “entomologist” we are as interested in the welfare of non-native birds as we are in native birds. 

“entomologist:”  “Doug Tallamy’s work shows this in the eastern US conclusively.”

Webmaster:  Professor Tallamy’s (University of Delaware) publications do not seem to be available on-line, which prevents us from reading his publications.  However, since he studies the insects on the east coast we don’t think whatever he reports trumps the studies that we have cited of insect populations here in the Bay Area. 

“entomologist:”     “I certainly feel for the loss of trees, but the alternative is that we accept a homogenized set of urban-tolerant plants and wildlife.  Maybe that’s ok if you don’t know the difference, but for those of us who actually pay attention it is profoundly sad.”

Webmaster:   We don’t see the logic of “entomologist’s” vision of a “homogenized” ecology.  If we destroy non-native plants and animals, our ecology will be less diverse.  And we hope that the readers of Million Trees will agree that we are, indeed, “paying attention.” 

 The Big Picture

 We suggest that “entomologist” and other native plant advocates step back from their deeply-seated prejudices against non-native plants and consider the big picture.  The fact is that insects are particularly vulnerable to climate change because they live in relatively narrow temperature ranges. (3) Although they are adjusting well to changes in vegetation, they are not likely to be able to make an equally successful adjustment to changes in temperatures.  Therefore, if our top priority is insects, we would be wise to reconsider destroying millions of non-native trees that are sequestering millions of tons of carbon, contributing to greenhouse gases and thereby to climate change.    

 

(1) Arthur M. Shapiro, “Exotics as host plants of the California butterfly fauna,” Biological Conservation, 110, 413-433, 2003

(2) Dov Sax. “Equal diversity in disparate species assemblages:  a comparison of native and exotic woodlands in California,” Global Ecology and Biogeography, 11, 49-52, 2002.

(3) “Mountain plant communities moving down despite climate change, study finds,” Los Angeles Times, 1/24/11

Non-native species are NOT the “second greatest threat to species in peril”

One of many doom and gloom scenarios used by native plant advocates to frighten the public into accepting their destructive “restoration” projects is the claim that “non-native species are the second greatest threat to the survival of species in peril.”(1)  Although the statement originates with a scientific study published in 1998, the context in which it was originally reported has long since been lost as it has been cited more than 700 hundred times in scientific studies according to Mark Davis.(2)

The original 1998 article in BioScience by Wilcove et.al. clearly states that the claim is not based on any actual data:

“We emphasize at the outset that there are some important limitations to the data we used.  The attributes of a specific threat to a species is usually based on the judgment of an expert source, such as a USFWS employee who prepares a listing notice or a state Fish and Game employee who monitors endangered species in a given region.  Their evaluation of the threats facing that species may not be based on experimental evidence or even on quantitative data.  Indeed, such data often do not exist.”(3)

This caveat is rarely repeated when the claim is invoked by native plant advocates to justify their crusade against non-native plants and animals.  In fact, since the statement was originally made over a decade ago, it is now repeated without reference to the original source.  It has acquired the status of a mantra amongst native plant advocates that requires no citation to substantiate its “truthiness.” 

The Wilcove et.al. article in BioScience in which this statement was made was heavily influenced by selecting a geographic area which is not representative of the United States as a whole.  Although Hawaii is a part of the United States its rates of extinction are not typical of the contiguous states of the union.  Rates of extinction are substantially higher on islands because they contain many more endemic (unique) species that do not occur elsewhere. These endemic populations are small and vulnerable to the introduction of competing species.  Native populations on islands are not supplemented by immigrations as they are elsewhere.   

Coqui frog is being eradicated in Hawaii. USDA photo

 

If Hawaii is removed from the anecdotal information in the Wilcove article, the rates of extinction are comparable to those in Canada where introduced species are considered the least important of six categories of causes of extinction (habitat loss, over-exploitation, pollution, native species interactions, and natural causes such as storms) identified in a similar article in 2006(4).  This list doesn’t include climate change, which is now considered a serious threat for extinction.    Similar studies in the continental United States have reached similar conclusions.(5)

At the time the Wilcove et. al. article was published there was no evidence of a single extinction (or even local extirpation) of a native plant in the continental US resulting from competition from an introduced species of plant.  Clearly, the authors of this study were guilty of exaggeration.(6) 

Although native plant advocates have misused this publication by taking it out of context, the authors were complicit in its misuse by selecting a geographic area that is not representative of the United States.   Non-native species are NOT the second greatest threat to the survival of endangered native species.  In fact, they probably aren’t the third, fourth, or fifth greatest threat to native species. 

 We wish that native plant advocates would examine the origins of their assumptions more carefully.  We believe if they did so they would modify their destructive projects to reflect a more inclusive view of nature. 

(1) Wilcove, DS, Rothstein, D., Dubrow, J., Phillips, A., and Losos, E, “Quantifying threats to imperiled species in the United States,” BioScience, 48, 607-615, 1998. 

(2) Davis, Mark, Invasion Biology, Oxford University Press, 2009, page 181.

(3) Ibid.

(4) Venter, O, et. al., “Threats to endangered species in Canada,” BioScience, 56, 903-910, 2006.

(5) Ibid., page 182

(6) Ibid., page 183

A dialogue about the living roof on the California Academy of Sciences

We encourage native plant advocates to comment on our posts because we learn from them.  We learn more about their ideology and the assumptions that support it.

These dialogues with native plant advocates are embedded in our posts and are therefore not as accessible to our readers as they often deserve to be.  Occasionally, we will create a post from these exchanges so that all of our readers can benefit from them.  In so doing, we hope not to discourage native plant advocates from posting comments, as they are essential to improving our mutual understanding of the complex issues we are debating.

We recently received a comment from someone who seemed to believe that our post about the green roof on the California Academy of Sciences is essentially fraudulent.   His accusations deserve a response.

California Academy of Sciences, April 2011

Comment from “Name Here”

May 6, 2011 11:43 am

Name Here:  “Since you don’t have the confidence to post your identity, I thought it only fitting to return the favor. Your argument would have much more strength if you were not anonymous.

You claim on your home page to provide citations, yet in this article you fail to tell us who “We had the privilege of meeting the ecology consultant who designed the plant palette for the living roof for the academy and many other institutions around the world.” is referring to. The “ecology consultant” does not have a name? By then throwing out Peter Del Tredici’s name it would appear as though you wish your reader to assume that he was the “ecology consultant” you refer to.”

Webmaster: The ecology consultant for the living roof on the Academy was Paul Kephart of Rana Nursery. He is the person we are quoting in our post about planning for the living roof.  Our readers can confirm Mr. Kephart’s role in the design of the roof by reading this article:  “High Maintenance Superstar,” Linda McIntyre, Landscape Architecture, August 2009.  This article is not available on-line, but the edition of the magazine in which it was published can be purchased on-line.  However, Mr. Kephart’s statement quoted in our post was made in a lecture to a group and does not appear in this publication. 

Our post did not state, nor did it imply that Peter Del Tredici was the ecology consultant for this project.  He is a scientist who has published articles about native plant “restorations,” particularly in urban settings.  We quote him in our post because his observations about native plant gardens are directly relevant to the living roof.

Name Here:  “On another note, you mention this third predominant species on the roof as “a moss” and then tell us it is non-native, yet offer no proof of this. Citing another blog with no standard of journalistic integrity is not a valid source. You might want to present the scientific name of this moss to prove your point, though I do not believe, judging by your writing, that you actually know the name, or you would have presented it.”

Webmaster:  At the time that we published our posts about the living roof, we did not know the names of the mosses on the roof, which is why we quoted the “From the Thicket” blog.  The author of the “From the Thicket” blog, Heath Schenker, is Professor of Landscape Architecture at UC Davis.  Her background and credentials are described on her blog.  She wrote her post about the living roof at the California Academy of Sciences after attending a symposium at the Academy about their monitoring project.  Our readers can judge for themselves if this was a credible source of information to document our post at the time it was published.

 Name Here:  “There are many different species of mosses out there, some native, some non-native. Many moss are very cosmopolitan in their range and therefore may occur natively all over the world. The actual quote from InTheThicket is as follows: “Nobody knows where the mosses came from, but they appear to be varieties of early-succession mosses, the types that commonly show up in disturbed soil.” I challenge you to show me where this says they are non-native.”

Webmaster:  After we published our post, the Academy made their monitoring report available on-line:  http://www.calacademy.org/pdfs/living-roof-project-results.pdf.  The report contained the names of the mosses on the roof: Bryum sp., Rosulabryum sp., Ceratodon purpureus, Leptobryum pyriforme.  We took that list to the Jepson Herbarium at UC Berkeley to confirm that our description of the mosses was accurate.  The staff at the Herbarium looked up those mosses for us and described them as “cosmopolitan,” which means they are widespread and cannot be considered either native or non-native.  Since these mosses were not amongst the 9 species of native plants originally planted on the roof, we felt comfortable with our original description of them.  They are clearly “volunteers,” not part of the original roof top planting.

Name Here:  “I think it is important for anyone reading this blog to be reminded that it is just that, a blog. It is written by an anonymous source who can say whatever they like with no fear of reprisal other than these comments, and with no need to live up to journalistic standards of any kind.”

Webmaster:  Yes, the Million Trees blog is “just a blog.”  However, I invite our readers to consider the difference between this accusatory comment from “Name Here” and the information we present.  We provide citations for most statements we make.  Those citations are usually of publications by academics at major universities, published in peer-reviewed journals or journalistic articles about their publications.  We often resort to journalistic articles because they are easier for non-scientists to comprehend. 

We know that we are confronting firmly held beliefs in the community of native plant advocates.  Therefore, we cannot expect to challenge their assumptions without providing well-documented information.  And since we have often been on the receiving end of ad hominem attacks by native plant advocates, we do our best to protect ourselves from such attacks by standing on firm scientific ground and by remaining anonymous.  (One wonders what “reprisals we should fear” for providing information with which “Name Here” disagrees.)

In contrast, “Name Here” questions our credibility without providing any evidence to substantiate his claim that we are fabricating information. Therefore, his comment seems more an attempt to discredit than to illuminate. 

Celebrating the first anniversary of the Million Trees blog

We are celebrating the anniversary of our first year of the Million Trees blog by reporting our progress and what we have learned. 

Our readership has grown steadily in the past year, particularly in 2011.  Daily visits have increased 200% since December 2010.

Of our 50 pages and posts, the three most popular posts, in descending order of visits, are presently:

A more recent post “The Living Roof:  A failed experiment in native plant gardening” is in fourth place, but gaining ground quickly.  There is apparently considerable interest in the green roof on the California Academy of Sciences.

We have had over 200 comments from readers, most in support of our perspective on the native plant movement, but many critical of our approach to this issue.  We have posted most, but not all of the critical comments. 

This comment is typical of those few that we chose not to post:  “This entire website is essentially just a cesspool of misinformation.”  We responded to that reader:  “If you would be more specific, we might post your comment.  You should also cite your sources as we do on Million Trees.  At the moment, your comment contains no information.”  He did not respond, so we did not post his comment.

Most native plant advocates who post comments are more specific, but they have never provided references for the generalizations that are the underpinnings of the native plant movement, such as:

  • Native grassland stores more carbon than forests (Since carbon storage is proportional to biomass, this is a physical impossibility.)
  • Native plants produce:  “Better soil function resulting in improved air quality and hydrology and pollination”  (We have seen no scientific evidence to support any of these claims.)
  • Wildlife prefers native plants (Most wildlife has adapted to non-native plants and is sometimes dependent upon them)

We responded to these comments with scientific references that contradict these claims and we invited the authors to provide us with scientific references that support their view.  We did not receive any replies to these requests for information about the sources of their statements. 

In one case, we had a long email dialogue with a native plant advocate who filled pages with such generalizations.  We repeatedly asked him to cite his sources.  Finally he sent us a 12 page bibliography, none of which he claimed to have read.  Nor did he make any connection between this lengthy bibliography and the statements he made in support of his arguments.  That was the end of the dialogue.

We conclude that these unsupported generalizations about the superiority of native plants are symptomatic of the native plant movement, which is an ideology, not a science.  The ideology persists because it is a victim of incestuous amplification, the sharing of misinformation by a group that isolates itself from dissenting views.  They hear their assumptions repeated so often that the assumptions are eventually transformed from fiction into fact in their minds. 

Unlike native plant advocates, we read all available literature on the subject, particularly publications in support of the native plant movement, such as the newsletters of the California Native Plant Society, Nature in the City, as well as Jake Sigg’s Nature News.  When we see new claims of the benefits of native plants, we research those claims by comparing them to the scientific literature. 

It is our research of the scientific literature that gives us hope that the native plant movement is losing its credibility.  In the past few years, more and more scientists have published their research refuting many of the assumptions of the native plant movement.  We have reported on Million Trees the research of some of these scientists:  Mark Davis, Peter Del Tredici, Hugh Raffles, and Dov Sax.   The publications of these scientists have enabled us to provide our readers with the evidence that many of the assumptions of the native plant movement are unsupported by scientific research.

Thank you to the readers of the Million Trees blog for visiting and commenting.  We invite our readers to correct any misstatements of fact, as we try our best to avoid the incestuous amplification that can accompany advocacy.  We provide citations of scientific literature whenever possible to avoid that trap.  We renew our appeal to native plant advocates to supply us with the scientific literature that they believe supports their ideology and we commit ourselves to reading and reporting such evidence. 

Our inclusive view of nature: native and non-native plants at Oyster Bay

For the record, we repeat Million Trees’ primary appeal to native plant advocates:  please plant native plants if that is your preference, but quit destroying non-native plants, trees and animals. 

Destructive "restoration" at Oyster Bay