Tag: hybridization

Money and Fire: 2022 Conference of California Native Plant Society

The California Native Plant Society (CNPS) held a conference in October for the first time since 2018.  There were two main themes of the conference:

Money:  The State of California is making a huge investment in the environment with many interrelated goals:

  • “30 X 30” is shorthand for the goal of protecting 30% of California’s land and coastal waters by 2030.
  • Developing “nature-based solutions” to address the threats of climate change.
  • Vegetation and forest management to reduce wildfire hazards.
  • Protecting and enhancing California’s biodiversity.

Fire:  The frequency and intensity of wildfire is of concern to all Californians, but the California Native Society has a particular interest in fire because it is viewed as a tool to enhance native plant abundance and control the spread of non-native plants that outcompete native plants.

Money

If attendance were the sole measure of success, the conference was a resounding success.  The conference was sold out with record-breaking attendance of 1,200 people.  That’s a 50% increase in attendance since 2018, when 800 people attended.  People came to learn about the many opportunities for public funding of their “restoration” projects and they were not disappointed.

Jennifer Norris, Deputy Secretary for Biodiversity and Habitat for the California Natural Resources Agency (CNRA) was one of the keynote speakers.  She and many other staff of CNRA made presentations at the conference to inform the community of native plant advocates about the many new opportunities to obtain grants for their projects.  This slide (below) shown at the conference, itemized by state agencies the $1.631 Billion budget for just the 30 X 30 portion of the CNRA’s environmental grant programs.  It does not include Cal-Fire funding for forestry projects to reduce wildfire hazards and address climate change.  Nor does it include $10 million of new funding for Weed Management Areas, which funds projects that attempt to eradicate non-native plants and $10 million of new funding for the state council for invasive species. State funding is also supplemented by new federal funding in support of a national goal of achieving 30 X 30. 

But money isn’t the only element of this state program that native plant advocates are excited about.  They have also been gifted a three-year moratorium on requirements for Environmental Impact Reports for their projects.  There will therefore be no requirements for a public process to review plans and comment on them. 

An anxious applicant for state grant funding asked a speaker representing the Wildlife Conservation Board about a rumor that projects using herbicides would not be funded.  The speaker’s reassuring answer was, “We are not rejecting projects using herbicides.” Applicants are being asked to complete a questionnaire about herbicides they plan to use, but the speaker was quick to add, “We have not rejected any [such applications] so far.”  She assured the audience that “You are all careful” in your use of herbicides.

Huge buckets of money are being distributed with no restrictions on the use of herbicides and no vetting process such as an environmental impact review with opportunities for the public to comment.  It seems inevitable that some of the projects will unintentionally do more harm than good, and the public will have nothing to say about which projects are funded. 

Fire

Alexii Sigona was the first keynote speaker for the conference.  He is a member of the Amah Mutsun-Ohlone Tribal Band (not a federally recognized tribe) and a Ph.D. candidate at UC Berkeley in the Department of Environmental Science.  He explained that there are 600 recognized members of the Amah Mutsun Band in a wide region around Pescadero, Hollister, and San Juan Bautista.  They collaborate with organizations such as CNPS because they don’t have the resources to manage their ancestral tribal lands.  He described some of the projects they engage in:

  • Landscape scale removal of “invasive” plants.
  • Plug planting of 120,000 native grass plants.
  • Creating “native hedgerows” for food sources.
  • Removal of native Douglas Firs “encroaching” on grassland.  They have removed 5,000 native Douglas fir trees.  He acknowledged that this project caused some concern about erosion and aesthetics.  Removal of native Douglas fir was mentioned by several other speakers during the conference.  It is an example of the preference of native plant advocates for grassland because it is the pre-settlement vegetation.  Native coyote brush is another target of eradication projects that attempt to prevent natural succession of grassland to other vegetation types. 

There is great interest among native plant advocates in the land management practices of Native Americans because controlled burns were Native Americans’ most important tool to maintain grassland species needed for food and for their prey.  Controlled burns are important to native plant advocates because they believe they are beneficial to native plants and help to control non-native plants.  Prescribed burns are also currently popular with many public land managers and they are the current fad among many fire scientists. 

Two presentations at the conference suggest that prescribed burns are not compatible with the preservation of native chaparral, nor are they capable of converting non-native grassland to native grassland.

This (above) is the concluding slide of Jon E. Keeley’s presentation.  Dr. Keeley is a respected fire scientist with US Geological Service with expertise in chaparral species.  He explained that 60% of native chaparral species (notably manzanita and ceanothus) are obligate seeders that do not resprout after fire and therefore depend on the existence of their dormant seed bank for regeneration.  In recent decades the fire interval in chaparral has decreased due to climate change and associated drought.  In many places, the fire interval has become too short to establish the seed bank needed for regeneration.  In those places Dr. Keeley has observed vegetation type conversion to non-native annual grasses. 

Dr. Keeley Is concerned that vegetation type conversion from forests in some cases and shrublands in others to non-native annual grassland may be the result of shortening fire intervals further “because of the upsurge in state and federal programs to utilize prescription burning to reduce fire hazard.” (1) This concern extends to some conifer species that do not resprout.  Some are serotinous conifers whose cones are sealed shut and do not release their seeds in the absence of fire. 

This is a familiar theme for much of Dr. Keeley’s research.  He asks that land managers balance the conflicting goals of resource management and fire hazard reduction. 

This (above) is the concluding slide (sorry for the poor quality of my photo) of a presentation about a 20-year effort at the Santa Rosa Plateau Ecological Reserve to convert non-native annual grassland to native grassland, using annual (sometimes bi-annual) prescribed burns.  Many different methods were used, varying timing, intensity, etc.  The abstract for this presentation reports failure of the 20-year effort:  “Non-native grass cover significantly decreased after prescribed fire but recovered to pre-fire cover or higher one year after fire.  Native grass cover decreased after prescribed fire then recovered to pre-burn levels within five years, but never increased over time.  The response of native grass to fire (wild and prescribed) was different across time and within management units, but overall native grass declined.” (1)

The audience was audibly unhappy with this presentation.  One person asked if the speaker was aware of other places where non-native grass was successfully converted to native grass.  The speaker chuckled and emphatically said, “NO.  I am not aware of any place where native grasses were successfully reintroduced.” 

Another questioner prefaced her question with the admission that “I’m new here and all this is new to me.”  Then she suggested that Native Americans are having some success using prescribed fire and that they should be consulted.  The speaker graciously replied that she planned to do so. 

Keep in mind that Native Americans weren’t historically using prescribed fire to convert annual grasses to native grasses.  Their burns were intended to maintain native grassland in the absence of competing non-native annual grassland.  Their objectives were different and they were operating in a very different climate and environment. 

Estimates of the pre-settlement population of Native Americans in California range from 138,000 to 750,000.  The population of Native Americans is estimated to have been reduced to as few as 25,000 after the arrival of Europeans due to disease and violence.  There are now over 39 million Californians and only 630,000 of them were Native Americans in the 2020 census.  Land management practices that are suitable for a population of less than 1 million seasonally migrating Californians are not necessarily suitable for a population of over 39 million sedentary Californians.   

The futility of trying to eradicate non-native plants

The Invasive Spartina Project (ISP) is another 20-year eradication project that is doomed to failure.  The presentation about the ISP was bravely made by Dr. Debra Ayres, one of the creators of the ISP in 1998.  With intensive effort and hundreds of gallons of herbicide (imazapyr), non-native spartina marsh grass has been greatly reduced in the San Francisco Bay, but the hybrid of non-native S. alterniflora and native S. foliosa persists.  Dr. Ayres explained why:

The spartina hybrid is reproductively stronger in every way than either of its parent species.  Dr. Ayres predicts that the hybrid will eventually replace both of its parent species:

If the goal of this project was to eradicate non-native spartina, hybrid spartina will accomplish that goal. You might think that this prediction would end the futile attempt to eradicate the hybrid, but you would be wrong.  There is no intention of abandoning this 20-year project.  More funding is assured by the California Coastal Conservancy and the project continues to provide well-paid jobs. 

Dr. Ayres ended her presentation with this enigmatic statement:  “Evolution doesn’t stop just because we think it has to.”  She seems to acknowledge that humans cannot stop evolution, yet she seems to recommend that we continue to try doing so.  If those positions seem contradictory, that’s because they are.  The bottom line is that as long as public funding continues to be available, this project will continue.

A central theme of the nativist agenda is the futile desire to prevent hybridization because it has the potential to replace a species considered “native.”  They fail to understand that hybridization is an important evolutionary tool that helps plant and animal species adapt to changes in environmental conditions by favoring traits that are better adapted to new conditions.  Humans cannot stop evolution, nor should we try.

San Francisco

I have a special interest in San Francisco because I lived there for nearly 30 years.  The native plant movement is very strong in San Francisco and there were several presentations about the success of the movement at the conference.

Sunset Blvd being built on barren sand in 1931

One of the projects is trying to turn Sunset Blvd on the western side of San Francisco into a native plant garden.  I lived in that district and am therefore familiar with Sunset Blvd as the major north-south traffic artery through the district.  It is important as the only wind break in the windiest district of the city, which is only 13 short blocks from the ocean.  The district is virtually treeless because of wind conditions and the pre-settlement landscape of barren sand.  Sunset Blvd is therefore the oasis of the Sunset District.  In the past, it was the only place to take a long walk in the shelter of the tall Monterey pines and cypress and tall-shrub understory.  The lawn beneath the trees was the only place for children to play close to their homes.

San Francisco’s Department of Public Works (DPW) is responsible for maintaining the medians in San Francisco.  It was therefore DPW’s responsibility to replace the wind break on Sunset Blvd that is dying of old age.  That’s not what they chose to do.  They are replacing the lawn with native shrubs and the tall trees with small native trees that won’t provide shelter from the wind. 

The spokesperson for DPW acknowledged that the project is controversial.  Neighbors of Sunset Blvd valued the sheltered recreational space provided by the 2.5 mile-long and wide median.  Native plant advocates and their allies want to create a wildlife corridor through the western edge of the city.  The spokesperson for DPW said that their plans are a compromise between these different viewpoints.  I don’t know if the neighbors agree, but I can say that native plant advocates are thrilled with the new native plant gardens on Sunset Blvd based on their presentation at the CNPS conference.

Planting Sunset Blvd. with native plants, December 2020

Native plant advocates prevailed on Sunset Blvd because CNPS bought or raised all the native plants and provided volunteers to plant them and maintain them for 3 years.  DPW couldn’t look their gift horse in the mouth. DPW hired 6 new gardeners to support maintenance of Sunset Blvd. This is an example of how the money that is flowing into such projects will transform many places into native plant gardens. 

Sunset Blvd and Taraval, spring 2022

So, let’s look at the result of these projects.  Presenters of these projects showed many beautiful pictures of newly planted native gardens on Sunset Blvd (above).  The pictures were taken in spring, when native plants briefly flower.  But that’s not what these places look like most of the year.  They will look better if they are irrigated year-round, but that would defeat the purpose of replacing the lawn to reduce water usage.  Unlike native plants, lawn turns brown during the dry season if it isn’t watered, but it is still functional as walkable ground. 

Here’s what that garden at Sunset Blvd and Taraval looks like most of the year:

Sunset Blvd & Taraval, October 23, 2022

There was also a presentation by a spokesperson from San Francisco’s Public Utilities Commission (PUC) about the creation of rain gardens in San Francisco.  San Francisco’s sewer system was built long ago when regulations did not require the separation of street run off from residential sewage.  When it rains, the sewage treatment plant is overwhelmed by street run off.  The sewage treatment plant releases untreated sewage and run off into the ocean, in violation of federal standards for water treatment. 

Rain garden on Sunset Blvd as shown at the CNPS Conference
Rain Garden on Sunset Blvd in August 2022. They aren’t pretty year around.

The PUC is developing rain gardens to redirect street run off away from sewage treatment plants into the ground so that treatment plants are not overwhelmed during heavy rain.  The San Francisco Chronicle recently reported that 151 rain gardens have been installed so far. It seems a very good idea, but native plant advocates are not happy with the rain gardens because the PUC has not made a commitment to plant exclusively native plants in the rain gardens.  The audience pressured the speaker about this issue.  He advised them to lobby the PUC to make a commitment to plant only native plants in the rain gardens.  I have no doubt that they will take his advice.  Given their influence and their access to public funding, I would be surprised if the PUC continues to resist their demands.

Conclusion

I have undoubtedly exhausted your patience, although there is much more I could tell you about, including several projects that look promising because they are exploring the importance of soil health to achieve successful results.

The conference themes in 2022 were consistent with the previous two conferences I have attended since 2015.  This is my summary of the fundamental errors of the nativist agenda in the natural world.  They are as apparent in 2022 as they were in 2015: 

  • The futility of trying to eradicate non-native plants that are better adapted to current environmental conditions.
  • The futile and harmful attempts to prevent natural succession and hybridization.
  • The contradictory goals of fuels management and resource management.
  • The lack of understanding that vegetation changes when the climate changes.  The ranges of native plants have changed and will continue to change.  The pre-settlement landscape of the 18th century cannot be recreated.
  • The lack of understanding of the importance of soil health to ecological restoration and associated ignorance (or denial) of the damage that pesticides do to the soil. 

(1) Abstracts for all presentations are available on the CNPS website.

Spartina eradication is now a zombie project

Over 20 years ago the governors of California, Oregon, and Washington made a commitment to eradicate non-native spartina marsh grass on the entire West Coast of the country.  Intensive aerial spraying of herbicide killed over 95% of non-native spartina about 10 years ago, but the project continues in the San Francisco Bay.  The goal is now the eradication of hybrid spartina that grows at the same marsh elevations as native spartina and is so visually similar that it requires 500 genetic tests every year to determine that it is a hybrid before it is sprayed with herbicide (1). This article will explain why the Invasive Spartina Project in the San Francisco Bay Estuary is now a zombie project, a project that is dead, but is not being allowed to rest in peace.

Click on the picture to see the presentation of the Invasive Spartina Project to the California Invasive Plant Council on June 11, 2021. This is the source of some of the information in this article. Answers to questions at the end of the presentation are particularly important.

Hybridization is the boogey man of plant nativism

Hybrid spartina is being hunted because it outcompetes native spartina.  Nativists fear the loss of native spartina as a distinct species.  Rather than seeing the potential for a new, improved species of spartina, they see it as a loss of biodiversity, rather than an increase in biodiversity. 

Non-native spartina is also accused of “invading” mudflats where some animal species require that type of environment. However, that accusation is contradicted by these photos where native spartina has been planted on mudflats at Eden Landing. The source of these photos is the June 2021 presentation of the Invasive Spartina Project.

Hybridization is an important evolutionary tool that frequently increases biodiversity by creating new species on the margins of ranges where closely related species encounter one another.  For example, hybridization is credited with creating over 500 species of oaks all over the world that are well-adapted to their respective microclimates.  The rapidly changing climate and the globalization of trade have created more opportunities for hybridization and resulting speciation. 

Advances in molecular analysis has informed us of the frequency of hybridization and its benefits to biodiversity:

“With the growing availability of genomic tools and advancements in genomic analyses, it is becoming increasingly clear that gene flow between divergent taxa can generate new phenotypic diversity, allow for adaptation to novel environments, and contribute to speciation. Hybridization can have immediate phenotypic consequences through the expression of hybrid vigor. On longer evolutionary time scales, hybridization can lead to local adaption through the introgression of novel alleles and transgressive segregation and, in some cases, result in the formation of new hybrid species.” 

Restoration and expansion of wetlands is extremely important as we prepare for anticipated rising sea levels.  If hardier, denser, stronger hybrid species of marsh grass are available why would we reject that opportunity?  Nativist ideology should not deprive us of this opportunity. 

Native species are not inherently superior to species that are better adapted to present environmental conditions.  The rapidly changing climate requires corresponding changes in vegetation to adapt to present conditions.  Extreme weather events are natural selection events that kill species that are no longer adapted to the climate.  We cannot stop evolutionary change, nor should we try.

Why does this matter?

If herbicides were not required to eradicate hybrid spartina perhaps I could shrug and move on.  Hundreds of gallons of imazapyr herbicide were used by East Bay Regional Park District to aerial spray non-native spartina for the first few years of the eradication project.  In 2020, EBRPD used 43 gallons of imazapyr for “ecological function,” a nebulous category that includes spartina eradication. 

When the Invasive Spartina Project (ISP) made a presentation to the California Invasive Plant Council in June 2021, the public asked several questions about the toxicity of the herbicide (imazapyr) that is used to eradicate spartina (1). The ISP mistakenly claimed that imazapyr is not harmful to humans and wildlife because it uses a different metabolic pathway to kill plants that does not exist in animals.  They probably believe that claim, but they are wrong.

 A similar claim was made for glyphosate for 40 years.  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.”

I asked Beyond Pesticides for help to determine if the exclusive pathway claim was true of imazapyr.  Beyond Pesticides informs me that both imazapyr and glyphosate use metabolic pathways that exist in animals. I summarize their response:  “You asked about the ALS pathway that is the target of imazapyr—is there a comparison to glyphosate?  [According to] the research I found, I think the comparison is valid.  This early paper appears to clearly state that ALS is a pathway found in yeast and bacteria as well as plants (2). Another early paper which identified ALS as coming from bacteria, fungi, and plants (3).”  These pathways exist in bacteria that reside in our bodies and perform important functions, particularly in our digestive and immune systems.  When we damage those bacteria, we are damaging our health.

Please note that both of these studies of imazapyr are nearly 40 years old.  If pesticides were being evaluated and regulated, the public and the users of imazapyr might know that it is harmful to animals.  I provided this information to the Invasive Spartina Project.  They responded that their use of imazapyr is legal.  Unfortunately, they are right.  Because there is no regulation of pesticide use in the United States, the Invasive Spartina Project has the legal right to use it.  But is it ethical?  I asked the Invasive Spartina Project to quit making the inaccurate claim that imazapyr kills plants, but cannot harm animals.  They did not respond to that request.

Unfortunately the judicial system is our only recourse to take dangerous chemicals off the market.  For example, chlorpyrifos that is known to damage children’s brains was finally banned as the result of a court order.  The EPA refused to ban chlorpyrifos, but a lawsuit finally resulted in a judge requiring that the EPA either provide studies proving its safety or ban its sale.  The EPA could not prove its safety, so it had no choice but to finally ban it. 

What about the animals?

Ridgway rail. Source: Cornell Ornithology Laboratory

The only issue that temporarily brought the spartina eradication project to a halt was the impact it has had on endangered Ridgway rail. Ridgway rail is a close relative to the Clapper rail on the East and Gulf coasts where the spartina species considered non-native here (S. alterniflora) is native.  Clapper rails are abundant where S. alterniflora resides.

“Fig. 2.  In marshes where invasive Spartina was present in large densities, populations declined rapidly commensurate with the amount of Spartina removed [from 2005 to 2011].” (4)

The eradication of Ridgway rail breeding habitat in the San Francisco Bay reduced the rail population significantly by 2011, according to the US Geological Service and the US Fish and Wildlife Service (4). The loss of rails was greatest where the most non-native spartina was killed with herbicide.  In response, USFWS mandated a moratorium on eradication in areas where rails were nesting (5). According to the ISP 2020 survey of rails in the project areas, the rail population rebounded where eradication was stopped.  When treatment resumed in 2018, the number of Ridgway rails in the previously restricted areas declined by 9% in the following year.  That outcome was predicted by the USFWS Biological Opinion: “In the 2018 Biological Opinion, the Service estimated that rails inhabiting the nine previously-restricted sub-areas may be lost due to mortality or exhibit decreased reproductive success due to loss of hybrid Spartina cover when treatment of these sub-areas resumed.”

Clearly, the endangered Ridgway rail has been harmed by spartina eradication, as USGS and USFWS concluded in their analysis that was published in 2016 (4):

“California [now known as Ridgway rail] rail survival was higher prior to invasive Spartina eradication than after eradication or compared to survival in a native marsh. The combined indication of these studies is that tall vegetation structure provides California rails with both higher quality nesting substrate and refuge cover from predation, particularly during high tides. Thus, habitat structure provided by invasive Spartina in heavily infested marshes may facilitate California rail survival, and continued efforts to remove invasive Spartina from tidal salt marshes could lead to further California rail population declines….” (4)

Given that Ridgway rail is protected by the Endangered Species Act, it is difficult to understand why this project is allowed to continue.  Much like the unregulated use of pesticides, it will probably take a lawsuit to enforce the Endangered Species Act on behalf of endangered Ridgway rail. When government is not functional, the judicial system can sometimes compensate.

Let’s bury this zombie project

The US Geological Service and the US Fish and Wildlife Service have put their finger on the failure of the Invasive Spartina Project.  The same could be said of many other pointless eradication projects:

“Removing the source of that novel habitat without addressing pre-existing native habitat quality limitations threatens to re-create an ailing landscape for California rails by dogmatically adhering to specific management approaches. In essence, the conservation community is choosing the winners and losers in this ecosystem by failing to solve the underlying problems that will support a healthy species community with all constituent members.” (4)

The spartina eradication project serves no useful purpose.  In fact, it damages the environment and the animals that live in it.  We cannot stop evolution, nor should we try.  Let natural selection determine the plant species that are best adapted to our environment and the animals that live in it.  Not only would we benefit from better protection for our coastline from rising sea levels, we could reduce our exposure to dangerous pesticides that are harmful to our health, as well as improve habitat for wildlife.  This project is doing more harm than good. 

  1. Presentation of Invasive Spartina Project to California Invasive Plant Council, June 2021 
  2. Falco, S.C., Dumas, K.S. and Livak, K.J., 1985. Nucleotide sequence of the yeast ILV2 gene which encodes acetolactate synthase
  3. LaRossa, R.A. and Smulski, D.R., 1984. ilvB-encoded acetolactate synthase is resistant to the herbicide sulfometuron methyl. Journal of bacteriology, 160(1), pp.391-394.
  4. M.L. Casazza, et.al., “Endangered species management and ecosystem restoration: finding the common ground,” Ecology and Society, 2016, 21(1):19. http://dx.doi.org/10.5751/ES-08134-210119
  5. Adam Lambert et.al., “Optimal approaches for balancing invasive species eradication and endangered species management,” Science, May 30, 2014, vol. 344 Issue 6187

Hybridization, a post script

We recently published an article in defense of hybridization, inter-breeding of two different species.  Conservation Sense and Nonsense defends hybridization because it is under fire from the native plant movement.  Many projects that needlessly destroy non-native plants (or one locally perceived as such) do so to prevent them from hybridizing with a native plant, which has the potential to cause a localized loss of a variant of a  native plant species.

This classic California poppy is eradicated in the Presidio in San Francisco because of fear it could hybridize with a sub-species of poppy that is considered “native” to the Presidio.

We are revisiting the topic because The Economist magazine recently published a comprehensive article about recent discoveries of the prevalence of hybrids among both plants and animals.  Until the advent of DNA analysis in the 1970s, the extent to which plant and animal species were the result of inter-breeding was largely unknown.  Also, conventional wisdom was that such inter-breeding was usually an evolutionary dead-end because offspring were often sterile, as exemplified by mules, the offspring of horses and donkeys.  In general, the consequences of hybridization were assumed to be negative.

Recent advances in DNA analysis have largely disproved these assumptions.  Hybridization is not only common, it can result in the creation of new species more rapidly than other forces of evolution, such as mutation and natural selection:  “Hybridisation also offers shortcuts on the long march to speciation that do not depend on natural selection at all.” (1)

Both the positive and negative effects of hybridization are real. In plants, the effects of hybridization are often beneficial because of plants’ unusually flexible genetics.  Plants, for instance, are frequently polyploid—meaning that each nucleus contains genomic copies in greater multiples than those of animals.  Polyploidy provides spare copies of genes for natural selection to work on, providing additional possibilities for selection.

Polyploidy confers another advantage. It creates a barrier to breeding with either parent species. That gives a new, emerging species a chance to establish itself without being reabsorbed into one of the parental populations. Recent evidence suggests that hybridization between two plant species in the distant past, followed by a simple doubling of the number of chromosomes in their offspring, may be responsible for much of the diversity in flowering plants that is seen today.

Plants seem to benefit from hybridization more often than animals. “For many animals, however—and for mammals in particular—extra chromosomes serve not to enhance things, but to disrupt them. Why, is not completely clear. Cell division in animals seems more easily confounded by superfluous chromosomes than it is in plants, so this may be a factor. Plants also have simpler cells, which are more able to accommodate extra chromosomes. Whatever the details, animal hybrids appear to feel the effects of genetic incompatibility far more acutely than do plants.” (1)

The Economist provides many important examples of hybridization among animal species, most notably the history of hybridization of our species, Homo sapiens.  We are now the sole surviving species of genus Homo.  Our genome contains the relicts of the genes of other members of our genus that are now extinct, which indicates hybridization with other hominoid species.  The modern human genome contains 1-4% of Neanderthal genes. 

The Economist article concludes, “This is a more complex conception of evolutionary history, but also a richer one. Few things in life are simple—why should life itself be?”   Keep your eyes and your mind open to new scientific knowledge that improves our understanding of life.

The bottom line

Biodiversity is the mantra of the native plant movement.  Native plant advocates claim that the primary purpose of saving native plants is preserving biodiversity.  But is it?  When non-native plants are eradicated, aren’t we depriving native plants of the opportunity to breed with a hardy new comer?  Are we preventing the creation of a new species by eliminating potential mates?  Are we dooming the native plant that is not adapted to survive the changing climate by depriving it of the opportunity to improve its survivability?

  1. The Economist, “Match and mix, hybrids and evolution,” October 3-9, 2020, page 67-70.  Available here:  Economist – hybridization and evolution

 

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

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

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

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

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

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

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

Sycamore. Selectree.

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

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

Western tiger swallowtail. Wikimedia

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

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

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

In conclusion

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

Conference of the California Native Plant Society

In January 2015, the California Native Plant Society (CNPS) celebrated its 50th anniversary by holding a gigantic conference.  About 700-1,000 people attended.  There were several hundred short presentations and many posters describing research and “restoration” projects.  The abstracts of these presentations are available on the CNPS website.  We are publishing a brief description of a few of the presentations sent to us by one of our readers who attended the conference.  We publish with permission but without attribution, on request.  We have added a few edits in brackets and italics as well as a few links to relevant articles on Million Trees.

I was very impressed with the quality of the presentations at the CNPS conference.  Some were given by academic scientists or their graduate students. Many were given by land managers and managers of “restoration” projects.  There were about 225 presentations in 5 simultaneous sessions, so it was possible to hear only about 45 of them. There were also many short “lightning” presentations and nearly 50 posters.  Please consider this an impression of the conference, rather than a comprehensive report.

Michael Soulé was the opening speaker.  You might recognize his name as one of the proponents of invasion biology who is angry about growing acceptance of “novel ecosystems” and the ecological functions they perform.  [Million Trees has posted articles about this debate among academic scientists.  Soulé is one of the invasion biologists who demanded that the Nature Conservancy abandon their support for novel ecosystems.]   His objection to any acceptance of non-native plants was the main focus of his presentation.  He closed by saying that he “cannot live” without wild nature.  Since his definition of “nature” seems to exclude non-native plants, one wonders how he will manage to survive.   Perhaps he lives in an alternate universe populated solely by native plants.

Trees in Paradise, by Jared Farmer
Trees in Paradise, by Jared Farmer

Jared Farmer was the speaker at the conference dinner.  His subject was the history of eucalyptus in California.  His presentation was similar to his treatment of the subject in his book, Trees in Paradise.  [Million Trees has posted articles about Farmer’s book.]  Like his book, his presentation was even-handed in its treatment of eucalyptus.  That enraged the audience, which booed every time he said something positive about eucalyptus.  One wonders why he was invited to speak to this audience.  Were the organizers of the conference interested in promoting a more balanced view of eucalyptus?  Or did they just want a provocative speaker to wake up a sleepy audience after hours of a fund-raising auction?

Many of the presentations were surprisingly frank about the difficulties experienced by “restoration” projects.  CNPS deserves credit for inviting speakers who described some stunning failures of their effort to “restore” native landscapes.  I’ll describe just a few of the themes of speakers I heard.

San Francisco’s Public Utilities Commission

I was surprised to learn that San Francisco’s Public Utilities Commission (PUC) is heavily engaged in native plant “restorations.”  The PUC is responsible for managing thousands of acres of open space in the watershed that supplies San Francisco’s drinking water.  Common sense suggests that the PUC’s top priority would be the purity and safety of the water supply.  The PUC presentations at the conference suggest otherwise.  The PUC’s commitment to native plant “restorations” seems to trump the goal of clean water.

The PUC attempted to “restore” 100 acres of wetland and riparian habitat in San Mateo, Alameda, and Santa Clara counties by planting over 500,000 native plants, obtained from several different nurseries.  They claim to have followed a strict protocol which theoretically should have prevented the introduction of diseased plants.  Their protocol obviously failed.  The fact that many of the plants were infected with Phytophthora was not discovered until they were planted in the ground.  Phytophthora is the pathogen that is causing Sudden Oak Death.  The PUC is now faced with the difficult—if not impossible—task of trying to contain the spread of a fatal pathogen for which there is no known cure.

This project was funded by a “mitigation” grant for capital projects elsewhere in San Francisco.  Environmental laws require the builders of new development to “mitigate” for the impact they have on the environment by funding projects elsewhere, which are considered beneficial to the environment.  This often looks like legalized extortion to me.  It also increases the cost of infrastructure improvements, which limits the number of improvements we can make.  In this case, there clearly was no benefit to the environment.  It was both money down the drain and a poke in the environment’s eye.

As pointless as that project seemed, the other project presented by the PUC seemed even more pointless.  They presented a poster describing an experiment intended to determine the most effective application method and type of herbicide to eradicate coyote brush.  They used several different methods and types of herbicide, including Garlon (triclopyr) [which is known to be very toxic to aquatic life] and Milestone (aminopyralid) [which is banned in the State of New York because it is persistent and very mobile in the soil].

Detail of poster about PUC project, CNPS Conference
Detail of poster about PUC project, CNPS Conference

As you know, coyote brush is a native plant, so one wonders why it was necessary to eradicate it.  According to PUC’s poster, it’s another example of trying to prevent natural succession from grassland to scrub.  You might ask why the PUC is obligated to maintain grassland?  You might also ask how the PUC can justify using toxic herbicides in our watershed?  I can’t answer those questions.  It doesn’t make sense to me.

San Bruno Mountain

Mission Blue butterfly. Wikimedia Commons
Mission Blue butterfly. Wikimedia Commons

There was also a discouraging presentation by the folks who have been engaged in the effort to “restore” San Bruno Mountain in order to preserve and maintain a population of several species of rare butterflies, including the endangered Mission Blue butterfly.  This project officially began 32 years ago when the Habitat Conservation Plan was created by federal environmental protection laws.  The goal was to restore native grassland required by the rare butterflies.  The speaker said this goal remains largely unfulfilled.  As for the butterflies, their current status is largely unknown because monitoring efforts are not sufficient to determine the size of the population.

While non-native plants considered “invasive” are a part of the problem in achieving the goal of this project, the biggest problem is, in fact, a native plant.  Once again, natural succession from grassland to native scrub, dominated by coyote brush, is the main reason why grassland continues to shrink on San Bruno Mountain:

“Although the last mapping effort in 2004 reported 1296 acres of grassland, we believe that many of these areas are in imminent threat of scrub encroachment and could be converted to scrub after a good coyote brush recruitment year. Large patches of contiguous grassland with less than 2% scrub cover are quickly vanishing…Baccharis pilularis (coyote brush) accounts for the majority of the scrub encroachment observed on San Bruno. It seems to follow the well documented pattern of episodic establishment in wet seasons when roots can more quickly tap into needed soil water. Once seedlings have survived the first critical year, mortality drops quickly and full establishment plays out over the next 5-7 years (Williams et al. 1987). During this process of establishment, grassland resources decline and eventually disappear. Soil changes such as increased nitrogen and allelopathic compounds often follow scrub encroachment (Zavaleta and Kettley 2006, Weidenhamer and Callaway 2010) reducing the ability of grasslands to successfully re-establish without an intermediate disturbance such as a fire or intensive browsing (Hobbs and Mooney 1986).” (1)

San Bruno Mountain from Daly City. Wikimedia Commons
San Bruno Mountain from Daly City. Wikimedia Commons

It’s seems almost comic that when all is said and done, the main threat to native grassland “restoration” is apparently a native plant that is just doing what comes naturally…”invading” grassland in the absence of fire or grazing.

Hybridization:  Friend or foe?

Dieteria canescens variety canescens, native to Wyoming and other western states. Photo by Stephen Perry.
Dieteria canescens variety canescens, native to Wyoming. Photo by Stephen Perry.

I also attended the presentation of a native plant advocate from Mammoth Lake, on the eastern side of the Sierras.  She is engaged in a futile crusade to prevent the hybridization of a new plant, which she considers non-native, with a closely related native plant.  When this new plant arrived in her neighborhood, she recognized that it was different, but she was unable to identify it.  It wasn’t easy to find someone who could identify it.  Eventually, she found a botanist in Wyoming (where it is native) who was able to tell her that the new plant is a variety of a plant that is native at Mammoth Lake.  These plants are in the aster family.  The native is Dieteria canescens.  The new plant considered a non-native invader is Dieteria canescens var. canescens.  In other words, they are the same species!

From a horticultural standpoint, the new plant is superior to the native in every way: it is a bigger plant with more flowers; the flowers are bigger with more rays; the flowers are a deeper color.  So, why must it be eradicated?  Because native plant advocates fear that it will hybridize with the native aster and “swamp” it genetically, i.e., wipe it out.  Would that be such a terrible thing?  That is a matter of opinion.

Dieteria canescens, native to Mammoth Lake. Photo by Steve Mason
Dieteria canescens, native to Mammoth Lake. Photo by Steve Mason

One person in the audience asked why the new plant was not being accepted as an adaptation to climate change that would probably increase the likelihood of the survival of the species.  The speaker’s answer was that she could not accept the loss of the variety she considers native.  Another person in the audience asked this rhetorical question:  “What is our narrative here?  How can we expect the public to understand that it is necessary to eradicate a plant that is the same species?” The speaker agreed that it is not an easy sell.  I was encouraged by these questions.  They seem to be a glimmer of common sense.  I hope they are prophetic of the future of the native plant movement.

On that happy note, I close with an invitation to visit the CNPS website to read the abstracts of the hundreds of posters and presentations at this excellent conference.

  1. “Assessment of the past 30 years of habitat management and covered species monitoring efforts associated with the San Bruno Mountain Habitat Conservation Plan (Draft),” Creekside Science, October 21, 2014.

A happy ending for the “Africanized” bee

Africanized honeybee USDA
Africanized honeybee USDA

Bees were imported from Africa to Latin America in the 1950s by Brazilian researchers.  They planned to breed them with European honeybees to improve honey production because the African bees were believed to be hardier than their European cousins.  When the bees escaped from the laboratory, researchers learned that the African bees were also more aggressive than European honeybees.

When African bees began to spread throughout Latin America, they became one of the first media-promoted panics about “invasive” species.  The media reported that the bees were capable of swarming and killing people and animals and they predicted that the bees would eventually spread throughout the United States.

Like most of the media-promoted panics about “invasive” species, predictions about Africanized bees were eventually discredited.  The “invasion” stopped in Texas because cold winters prevented their movement further north.  And the extreme aggressiveness of the bees also proved to be an exaggeration, partially because interbreeding with the European honeybee moderated the behavior of the African bees.

The benefits of new species

Scientific American reports that after 60 years of interbreeding, bee researchers say the original goal of an improved bee species for Latin America has been achieved.  Hybridized bees have benefited from some of the characteristics of their African cousins.

  • Africanized bees are more resistant to parasites because they groom themselves more often than European bees.
  • Africanized bees are more aggressive foragers and are capable of finding nectar and pollen sources where European bees would not.

This interbreeding was accomplished by the bees themselves:  “…it is not even accurate to call them Africanized bees anymore.  After decades of a massive and uncontrollable continent-wide wild breeding experiment, the African-Italian hybrid has morphed into a totally new bee unlike either parent species.” (1)

Now bee researchers are trying to breed new varieties of bees that are tailor made for specific conditions.  For example, where humans are stealing honey, a more aggressive bee with more of the characteristics of the African bees may be best suited.  In places where mites are a problem, bee keepers will want a “bee that obsessively cleans itself.”

Personally, we prefer the earlier scenario, in which the bees sorted it out amongst themselves.  We are deeply suspicious of the claims of humans that we are capable of producing better results than nature can accomplish on its own. More often than not, the results of human interference are unintended consequences, if not disastrous.

Does this sound familiar?

This story is a familiar refrain for the readers of Million Trees:

  • New species should not be assumed to be “bad” species.
  • Problems caused by new species are often resolved without our interference.
  • New species often make positive contributions to ecosystems.
  • Methods used to eradicate new species are often futile as well as more harmful than the mere existence of new species.
  • Hybridization should not be viewed as a problem.  Particularly at a time of a rapidly changing climate, hybridization often facilitates natural selection, resulting in a new species which is better adapted to current conditions than its predecessors.

**************************

(1) Erik Vance, “Bee Researchers Make Friends with a Killer,” Scientific American, December 11, 2013

Hybridization is an adaptive strategy for species survival

Large ground finch. Linda Hall Library

We introduced Darwin’s finches to our readers in our previous post.  We told you about the research of Rosemary and Peter Grant on the Galápagos Islands that documented the rapid adaptation of the finches to radical changes in their food sources resulting from extreme weather events.  In this post we will continue the story by telling you about another of the amazing discoveries of the scientists studying the finches over a period of nearly 30 years.

Natural selection resulted in the survival of finches with body sizes and shapes that were best suited to the availability and type of food.  Sexual selection enhanced those physical characteristics during periods in which females had more choice because they were greatly outnumbered by males.  In addition to these adaptations, the birds increased their cross-breeding with other species and the resulting hybrids actually had a survival and breeding advantage over their species “pure” parents.*

In the first five years of the research study, there was little evidence of different finch species interbreeding, known as hybridizing.  On those rare occasions when species interbred, the resulting generation was not as successful as their parents, with respect to finding a mate and raising another generation.

Such lack of success of hybrids is considered the norm in nature.  In fact, many hybrids are sterile, incapable of reproducing.  Think of the sure-footed but sterile mule—the offspring of a horse and a donkey—as the classic example of a hybrid.

After the severe drought of 1977 and the flood of 1983, the Grants began to notice an increasing number of cross-breeding birds.  It seemed that the resulting hybrids were having more breeding success than the pre-drought hybrids and the data confirmed their observation.

This counter-intuitive conclusion required some careful consideration and the conclusion is a valuable lesson in our rapidly changing environment.  The environment on the islands was radically transformed by the severe drought and subsequent flood.  The cactus was overwhelmed by a vine that smothered it.  The plants with big, hard seeds were attacked by a fungus that decimated the population.  The small seeded plants thrived and became the dominant food source.

The rapidly changing environment was causing more rapid evolution and the genetic variability of hybrids was giving them an advantage.  If the environment is changing rapidly in unpredictable ways, the birds could increase the odds of finding a winning strategy by increasing the variability of their genes, sometimes resulting in novel traits.

We cannot and should not, however, anthropomorphize the birds by imputing motives to the selection of a mate of another species.  The starving cactus finch probably observes that a male of another species—a seed-eating ground finch, for example—appears to be more fit than a male of her own species.  She is not thinking of the odds of increasing genetic variability.  Natural selection operates without the conscious effort of species.

The implications of hybridization

We are experiencing a period of rapid change because of the anthropogenic (caused by humans) impacts on the environment, most notably climate change, but surely many other impacts which we don’t necessarily understand.  These would seem the ideal conditions for the hybridization of species which speeds up evolution by increasing genetic variability. 

Unfortunately, one of many strategies of the native plant movement and nativism in the animal kingdom is to prevent hybridization because it is perceived as a threat to native plants and animals.  We have reported to our readers some examples of such attempts to prevent hybridization and there are many more in the literature:

The variety of California poppy being eradicated from the Presidio in San Francisco.

Are efforts to prevent hybridization depriving plant and animal species of opportunities to adapt to the rapidly changing environment?  We don’t know the answer to that question, but we find it a provocative line of inquiry.

***************************

*This information is drawn from:   Jonathan Weiner, The Beak of the Finch, Vintage Books, 1994

Hybridization: “Genetic pollution” or a natural process?

 
Presidio variety of California poppy. NPS photo

The San Francisco Chronicle’s gossip columnist, Leah Garchik, recently published a story about California poppies in the Presidio.  Apparently, someone planted the “wrong” poppy, or it migrated there.  The poppy that is native to the Presidio is small and yellow.  This “alien” poppy is the large orange poppy that most of us consider the classic California poppy.  The historical record indicates that this classic poppy grew elsewhere in San Francisco, but since it didn’t grow in the Presidio it must be removed because the Presidio’s Vegetation Management Plan “contains the requirement to remove any plants that could jeopardize the integrity of the genetics of native plants in the Presidio.” 

The “wrong” poppy

This incident reminded us of an article published in the newsletter of the local chapter of the California Native Plant Society several years ago, entitled “Contaminating the Gene Pool.”  In this article Jake Sigg instructs gardeners to beware of planting the wrong variety of a native plant because it will cause “genetic pollution.”  The California poppy is one of the examples he gives of a variety of California native being planted in San Francisco that doesn’t belong here.  It isn’t sufficient in his opinion, to plant a California native if that specific variety of the species didn’t historically occur in San Francisco.  He asks gardeners to “think in terms of preserving the genetic integrity of the local landscape.”  And he speculates many negative consequences of selecting the wrong variety, such as “genetic swamping, you’ve got all these foreign genes that are going to overwhelm the native population.”  We were reminded of Mr. Sigg’s vocal opposition to human immigration. 

For the benefit of our readers who aren’t gardeners, we should explain what Jake Sigg and the Presidio are worried about.  In a word, they are worried about hybridization, defined as “to breed or cause the production of a hybrid,” which is defined as “the offspring of two animals or plants of different breeds, varieties, or species.”  Hybridization is as likely to occur between two native plants as two non-native plants, but native plant advocates are concerned about the possibility of a native and a non-native plant producing a hybrid variety that is distinct from the native plant.  Hybridization is not inevitable, but it does occur naturally as well as through human manipulation.  The “From the Thicket” blog recently told the fascinating story of the development of a valuable garden cultivar variety of a favorite California native, ceanothus or California Lilac. 

Aside from the unpleasant association with eugenics, Mr. Sigg’s advice raises several practical questions.  How is the gardener supposed to know exactly which variety of a native plant “belongs” in San Francisco or even in a specific neighborhood within San Francisco, such as the Presidio?  And, in the unlikely event that gardeners might have such esoteric knowledge, where would they get the seeds of this specific variety?  Jake Sigg acknowledges this practical obstacle, but advises gardeners to get their seeds and plants only from the annual plant sale of the local chapter of the California Native Plant Society.  One wonders how many gardeners will follow this rather restrictive advice.

However, the more important question is the scientific question.  Is hybridization an inherently harmful process that always reduces species diversity?    We turn to Mark Davis for a less gloomy view of hybridization.  Like most scientific questions, there is evidence of both positive and negative effects of hybridization on species diversity.  Since you’ve heard the negative view from Mr. Sigg, we’ll let Mark Davis speak for the positive view.  Professor Davis reports in his book Invasion Biology* that “the fossil record generally shows that following the invasion of new species, the number of species resulting from adaptive radiations and evolutionary diversification exceeds the number of extinctions.”   And he concludes his discussion of hybridization and evolution by saying, “…a fair appraisal must also acknowledge that species introductions can enhance diversity as well, through hybridization, and the creation of new genotypes.”

The native plant movement has a narrow view of nature, which we do not share.  Their ideology is based on dire predictions of ecological disaster if we don’t follow their restrictive advice.  And when the managers of public lands choose to follow their advice, the consequences are usually the destruction of plants and animals that we value, in this case a field of California poppies. 

* Mark Davis, Invasion Biology, Oxford University Press, 2009, page 78-82.