June 2020 – Conservation Sense and Nonsense

Deforestation and Climate Change

Climate change is the environmental issue of our time. The fact that the climate is warming is indisputable and the consequences of the changes are becoming more evident. Much of California has warmed over 3⁰ F since 1980.

Consequences of Climate Change

The impact of climate change on biotic and abiotic realms has been far-reaching:

Sea Level Rise: Temperatures in Polar Regions have increased the most because the ice is melting and sunlight that was reflected by the ice is now absorbed by the darker surface. Melting ice has raised sea levels between 1993 and 2017 on average 3.1 mm (1/8th inch) per year at an accelerating rate. The Intergovernmental Panel on Climate Change (IPCC) predicts that sea levels will rise .8 meter (2.6 feet) by the end of the century. Coastal cities are flooding during high tides and storm surges. Islands are disappearing.
Warming Ocean: Marine life is dying in warming waters and coral reefs are dying because the water becomes more acidic as it absorbs more carbon dioxide (CO₂).
Extreme Weather Events: The increase in the frequency and severity of droughts, hurricanes, tornados, heat waves, etc. is attributed to climate change. These events kill plants and animals. Extreme temperatures will eventually make some places in the world uninhabitable for most life.
Wildfires: Increased frequency and intensity of wildfires all over the world are caused by global warming and associated drought.

Given the life-threatening conditions created by the warming planet, it seems a small quibble to argue about whether or not the landscape must be transformed into some semblance of what it was in the 14^th century, prior to global explorations and colonization by Europeans. We are doing next to nothing to address the causes of climate change, yet we are spending approximately $25 billion per year on such “restorations” of historical landscapes. When these projects kill trees, they make climate change worse. California is considered a leader in addressing climate change in the US. Yet, when calculating carbon loss to meet stated targets for reduction, California does not include carbon loss in the trees that are destroyed.

Causes of Climate Change

There is nearly universal agreement in the scientific community that climate change is caused by greenhouse gasses emitted by the activities of humans.

Note that “forestry” (more accurately described as “deforestation”) contributes more greenhouse gas emissions than transportation. In both cases, carbon dioxide (CO₂) is the specific greenhouse gas that is emitted by these sectors of the economy. In the case of transportation cars, airplanes, ships, etc. are using fossil fuels that emit CO₂ when burned. In the case of deforestation, the CO₂ that is stored by trees during their lifetime is released into the atmosphere as a greenhouse gas when the tree is destroyed and its wood decays. And the loss of the trees means there will be less carbon storage in the future. Even if new trees were planted, less carbon would be stored because carbon storage is largely a function of biomass; that is, bigger trees store more carbon:

Carbon Storage and Sequestration in San Francisco’s Urban Forest

d.b.h. = diameter at breast height, is the standard measure of tree size. The bigger the tree, the more carbon it stores. Source: US Forest Service inventory of San Francisco’s urban forest, 2007.

Forests cover 31% of the land area on Earth and annually 75,700 square kilometers (18.7 million acres) of the forest is lost as a result of wildfire, clearing for agriculture and grazing, and logging for timber. For the past 25 years, we have also been destroying trees just because they aren’t native. In California we destroy eucalyptus, Monterey pine and cypress outside their small native range, and a few other non-native species. In the Southwest we destroy tamarisk trees that were planted to control erosion. On the East Coast we destroy ailanthus (tree of heaven). In Florida we destroy malaleuca trees. Native plant advocates call these trees “invasive,” but a more accurate description is that they are successful trees, well adapted to current climate conditions. There are probably many other non-native trees on the long hit list of native plant advocates.

Other benefits of trees

Trees are valuable members of our communities for many reasons in addition to storing carbon.

Trees provide the windbreak that makes our parks and open spaces comfortable in windy coastal locations.
Trees are a visual and sound screen around our urban parks and residential properties.
Trees remove particulates from the air, reducing the air pollution that makes urban environments unhealthy.
The San Francisco Bay Area is very foggy during summer months. Tall trees condense the fog, which falls to the ground as rain, adding 10 inches of annual precipitation in East Bay eucalyptus forests and 16 inches of annual precipitation in San Francisco’s eucalyptus forests.
Forests transpire water from their leaves that falls back to earth as rainfall. Where forests are destroyed, rainfall decreases significantly.

Transpiration is the process by which moisture is carried from tree and plant roots to the leaves, where it changes to vapor and is released to the atmosphere. Interestingly, a large oak tree can draw 40,000 gallons of water a year up through the roots and evaporate that moisture through the leaves. Source: USGS

Trees stabilize the soil with their roots, preventing erosion on steep hillsides that become unstable when trees are destroyed.
The roots of trees absorb rainfall that would otherwise run off the land without being absorbed into the soil. The run off washes the top soil away, clogging rivers and streams and reducing the fertility of the soil.

Case Studies

We don’t need to speculate about the consequences of destroying trees because there are many specific examples of the negative impact of destroying large numbers of trees. Here are two examples, one modern and one historical.

The island nation of Comoros, off East Africa, once had an extensive cloud forest, a forest in which trees are often surrounded by low-level cloud cover. Cloud forests, such as the eucalyptus trees shrouded in fog on Mount Sutro in San Francisco, condense large amounts of moisture out of the clouds that then falls onto the ground. Fog drip in San Francisco’s eucalyptus forests adds sixteen inches of rainfall each year in those forests.

Eucalyptus canopy on east side of Glen Canyon Park, taken from Turquoise Way December 2012, before tree destruction began. Courtesy San Francisco Forest Alliance

The delicate ecosystem on Comoros was disrupted when the cloud forests were cleared to make way for farmland. Between 1995 and 2014 about 80% of the remaining forest was cut down. The loss of trees disrupted the rainfall cycle on the islands. The moisture that the cloud forest was condensing from the fog was lost to the ground when the trees were destroyed. That ground moisture was then no longer transpired back into the air by the trees that had been destroyed, resulting in less rainfall. The disruption caused waterways to dry out, and left once-fertile soil exposed to erosion, with the loss of nutrients in the soil that remains. Comoros has lost 40 permanent rivers in the last 50 years. There is no longer enough water for agriculture or the daily household needs of the population.

Restoring forests is a challenge, and cloud forest can be particularly difficult. “It’s impossible to replace it,” said a cloud forest specialist at the University of York in England. “You need to save them before they’re gone.” Comoros could be a lesson for those who want to cut down the cloud forest on Mount Sutro and elsewhere in the Bay Area. Disrupting the rainfall cycle could make our drought even more extreme.

Sutro forest on a typical summer day. Courtesy Save Sutro Forest.

Icelanders appreciate their trees because they have few of them. Iceland was heavily forested, mostly with birch trees, when the Vikings arrived in the 9^th century. Within 100 years, settlers cut down 97% of original forests to build housing and make way for grazing pastures. Now only 0.5% of the Iceland’s surface is forested, despite extensive reforestation efforts since the 1950s. Lack of trees means there isn’t vegetation to protect the soil from erosion and to store water, leading to extensive desertification.

Reforestation efforts in Iceland did not attempt to restore native birch forests because they store little carbon and they are not useful for timber. Seeds of pine and poplar from Alaska were introduced, but growth has been slow because the soil is nitrogen poor and the climate is very cold. The growth rate is estimated to be only one-tenth of the growth rate of tropical forests in the Amazon.

Both of these examples illustrate that when forests are destroyed, they are not easily replaced. Much like the historical landscape, we can’t go back. Nature is dynamic. It moves forward, not back.

Consequences of deforestation in San Francisco Bay Area

San Francisco has one of the smallest tree canopies—only 14%–of any major city in the Country:

Source: Data from Urban Forestry Plan, SF Planning Department, 2016. Graphic by San Francisco Forest Alliance

The small urban forest in San Francisco is storing carbon that would otherwise be released into the atmosphere as greenhouse gas, contributing to climate change. “Carbon sequestration is the process by which atmospheric carbon dioxide is taken up by trees, grasses, and other plants through photosynthesis and stored as carbon in biomass (trunks, branches, foliage, and roots) and soils. The sink of carbon sequestration in forests and wood products helps to offset sources of carbon dioxide to the atmosphere, such as deforestation, forest fires, and fossil fuel emissions.” (US Forest Service)

Carbon capture by above ground vegetation is proportional to biomass. Because Blue Gum eucalyptus is the largest and most common tree in San Francisco, most carbon storage in San Francisco’s urban forest is in eucalyptus trees, according to an inventory done by the US Forest Service, as illustrated by this graph of the inventory.

Carbon storage by tree species in San Francisco

All other trees in San Francisco inventoried by US Forest Service are also non-native because there are few native trees in San Francisco. There are few native trees in San Francisco because they are not well adapted to challenging conditions. The wind is strong and constant. The soil is sand, rock, or clay. It doesn’t rain for 7 months of the year. The trees that were planted in the San Francisco Bay Area in the 19^th century by European settlers were non-native because they were the species that could survive these harsh conditions.

The non-native trees that are being destroyed by public land managers in the San Francisco Bay Area will not be replaced because the goal of the land managers is to restore grassland that existed prior to the arrival of Europeans at the end of the 18^th Century. All the benefits of trees and forests, including carbon storage will not be replaced.

Forests store more carbon than grassland

Native plant advocates defend the destruction of our urban forest by making the inaccurate claim that grassland stores more carbon than trees. While it is true that more carbon is stored in the soil than in above-ground vegetation, it does not follow that the soil in grassland contains more carbon than the soil in forests. The US Department of Agriculture report, “Considering Forest and Grassland Carbon in Land Management” (2017) graphically illustrates that forests in the US store far more carbon per hectare than any other land type and grasslands store the least amount of carbon per hectare of undeveloped land in the Western United States:

The differences in carbon storage per hectare in Western and Eastern United States are caused by differences in climate, soil, and specific vegetation types. The USDA report also makes these statements about the value of forests for carbon storage:

The conversion of forest to non-forest should be avoided to preserve carbon storage, “Because mature forest stands are more likely to be carbon rich from the high volume of tree biomass and recovery takes a long time through afforestation…Further, soil carbon generally declines after deforestation from accelerated decomposition of organic matter such as litter and tree roots.”
“Across forest systems, the ‘no harvest’ option commonly produces the highest forest carbon stocks. Managed stands have lower levels of forest biomass than unmanaged stands…” In other words, from the standpoint of maximizing carbon storage, leave the forest alone!
“Fuel-reduction treatments lower the density of the forest stand, and, therefore, reduce forest carbon.” Again, the message is leave the forest alone!
“…carbon emissions from prescribed fire, the machinery used to conduct treatments, or the production of wood for bioenergy may reduce or negate the carbon benefit associated with fuel treatments…”

Misplaced priorities

I am mystified by the obsession with native plants. Still, I respect everyone’s horticulture preferences. If you prefer native plants, by all means, plant them. We make just one request: quit destroying everything else because the loss of our urban forest is contributing to climate change and depriving our communities of the many benefits of trees and forests.

Pesticides are the primary tool of the “restoration” industry

Over 20 years ago, my initial reaction to native plant “restorations” was horror at the destruction of healthy trees. It took some years to understand that pesticides are used by most projects to prevent the trees from resprouting and to control the weeds that thrive in the sun when the trees are destroyed. Herbicides are a specific type of pesticide, just as insecticides and rodenticides are also pesticides.

Because pesticide application notices are not required by California State law for most of the herbicides used by “restoration” projects, the public is unaware of how much herbicide is needed to eradicate non-native vegetation, the first step in every attempt to establish a native plant garden. California State law does not require pesticide application notices if the manufacturer of the herbicide claims that their product will dry within 24 hours.

Herbicides used to eradicate non-native plants

In 2014, the California Invasive Plant Council conducted a survey of 100 land managers to determine what methods they use to kill the plants they consider “invasive.” The result of that survey was a wakeup call to those who visit our parks and open spaces. 62% of land managers reported that they frequently use herbicides to control “invasive” plants. 10% said they always used herbicides. Only 6% said they never use herbicide. Round Up (glyphosate) is used by virtually all (99%) of the land managers who use herbicides. Garlon (triclopyr) is used by 74% of those who use herbicide.

Pesticide use by land managers in California. Source California Invasive Plant Council

Land managers in the Bay Area use several other herbicides in addition to Garlon and Round Up. Products with the active ingredient imazapyr (such as Polaris) are often used, most notably to kill non-native spartina marsh grass. Locally, the San Francisco Estuary Invasive Spartina Project (ISP) “defines a need for a zero tolerance threshold on invasive Spartina in the San Francisco Bay.” 2,000 acres have been repeatedly sprayed with herbicides on East and West sides of the San Francisco Bay since the project began. The result of this project has been bare mud where the imazapyr was aerial sprayed from helicopters the first few years of the project with annual spot spraying continuing 15 years later. Imazapyr is very mobile and persistent in the soil. That is the probable reason why attempts to replace the non-native species with the native species were unsuccessful. The loss of both native and non-native marsh grass has eliminated the nesting habitat of the endangered Ridgway rail, decimating the small population of this endangered bird in the Bay Area.

Pesticide Application Notice, Heron’s Head, 2012

Aminopyralid (brand name Milestone) is also used. Although it is considered less toxic than other herbicides, it is the most mobile and persistent in the soil. New York State banned the sale of Milestone because of concern about contaminating ground water.

With this knowledge of widespread use of herbicides by land managers, we followed up with specific land managers in the Bay Area to determine the scale of local herbicide use. East Bay Regional Park District significantly reduced their use of Round Up for facilities maintenance in 2018, in response to the public’s concerns after multi-million dollar product liability settlements of lawsuits from users who were deathly ill after using glyphosate products. In 2019, the Park District announced that it would phase out the use of Round Up in picnic areas, camp grounds, parking lots, and paved trails.

At the same time, the Park District restated its commitment to using herbicide to control plants they consider “invasive.” Unfortunately, the Park District’s use of herbicide for “resource management projects” has skyrocketed and is by far its greatest use of herbicides. “Resource management project” is the euphemism the Park District uses for its native plant “restorations” that begin by eradicating non-native vegetation such as spartina marsh grass and 65 other plant species.

These trends in pesticides used by East Bay Regional Park District continued in 2019. Glyphosate use continued to decline by 82% since reduction strategies began in 2016. Use of Garlon (active ingredient triclopyr) to control resprouts of non-native trees and shrubs increased 23% since 2017. Use of Polaris (active ingredient imazapyr) to eradicate non-native spartina marsh grass increased 71% since 2017. “Resource management projects” have been renamed “ecological function.”

San Francisco Recreation and Parks Department (SFRPD) reduced use of herbicide briefly in 2016, after glyphosate was classified as a probable carcinogen. However, herbicide use has since increased, particularly in the 32 designated “natural areas” where SFRPD is attempting to “restore” native plants by eradicating non-native plants. In 2019, SFRPD applied herbicides 243 times, the most since 2013. Of these, 144 applications were in the so-called “natural areas” (this includes properties of the Public Utility Commission, San Francisco’s water supplier, managed in the same way; i.e., eradicating plants they don’t like). Though the “natural areas” are only a quarter of total city park acres in San Francisco, nearly half the herbicides measured by volume of active ingredient were used in those areas.

Data source: San Francisco Recreation and Parks Department. Graphic by San Francisco Forest Alliance

San Francisco’s Parks Department has been using herbicides in these areas for over 20 years. Plants that are repeatedly sprayed with herbicides eventually develop resistance to the herbicide, just as over use of antibiotics has resulted in many bacteria that are resistant to antibiotics.

Spraying Garlon on Twin Peaks in San Francisco, February 2011

UC Berkeley recently announced a temporary ban on the use of glyphosate on playing fields and similar landscaped areas. The use of glyphosate to kill non-native plants considered “invasive” was specifically exempted from UC’s temporary ban.

The more pressure the public puts on land managers to restrict the use of herbicides, the more vociferous native plant advocates have become in defense of herbicides. In October 2017, California Invasive Plant Council published a position statement regarding glyphosate that justified the continued use of glyphosate, despite its classification as a probable human carcinogen by the World Health Organization.

Mounting public pressure to ban the use of glyphosate has also pushed land managers to try newer herbicides as substitutes (e.g., Axxe, Lifeline, Clearcast). Less is known about these products because less testing has been done on them and we have less experience with them. It took nearly 40 years to learn how dangerous glyphosate is!

Why are we concerned about herbicides?

The World Health Organization classified glyphosate (the active ingredient in Round Up) as a probable human carcinogen in 2015. That decision suddenly and radically altered the playing field for the use of glyphosate, which is the most heavily used of all herbicides.

Since that decision was made, many countries have issued outright bans on glyphosate, imposed restrictions on its use or have issued statements of intention to ban or restrict glyphosate-based herbicides. Countless US states and cities have also adopted such restrictions. Locally, the Marin Municipal Water District (MMWD) made a commitment to not using pesticides—including glyphosate—in 2015. MMWD had stopped using pesticides in 2005 in response to the public’s objections, but engaged in a long process of evaluating the risk of continuing use that resulted in a permanent ban in 2015.

Several jury trials have awarded plaintiffs millions of dollars as compensation for their terminal medical conditions that were successfully attributed to their use of glyphosate products by product liability lawsuits. There are an estimated 125,000 product liability lawsuits in the US against glyphosate awaiting trial.

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.”

It took lawsuits to establish the toxicity of glyphosate because the “studies” that are used to approve the use of pesticides in the US are done by the manufacturers of pesticides. The studies are manipulated, often with the active participation of government employees who are responsible for regulating dangerous chemicals. The lawsuits succeeded by revealing the fraudulent studies used to exonerate glyphosate.

What little research is done on the effect of pesticides on wildlife indicates that pesticides are equally toxic to animals. New research finds that western monarch milkweed habitat contains a “ubiquity of pesticides” that are likely contributing to the decline of the iconic species: “’We expected to find some pesticides in these plants, but we were rather surprised by the depth and extent of the contamination,’ said Matt Forister, PhD, a butterfly expert, biology professor at the University of Nevada, Reno and co-author of the paper…’From roadsides, from yards, from wildlife refuges, even from plants bought at stores—doesn’t matter from where—it’s all loaded with chemicals. We have previously suggested that pesticides are involved in the decline of low elevation butterflies in California, but the ubiquity and diversity of pesticides we found in these milkweeds was a surprise,’ Dr. Forister said.”

Damage to the environment

In addition to harming humans and other animals, herbicides used by native plant “restorations” are damaging the soil, undoubtedly contributing to the failure to successfully establish native plants. (1)

Both glyphosate (Round Up) and triclopyr (Garlon) are known to kill mycorrhizal fungi that live on the roots of plants and trees, facilitating the transfer of moisture and nutrients from the soil to the plants. The absence of mycorrhizal fungi makes plants more vulnerable to drought because they are less able to obtain the water they need to survive.
Glyphosate is known to bind minerals in the soil, making the soil impenetrable to water and plants more vulnerable to drought.
Both glyphosate and triclopyr also kill microbes in the soil that contribute to the health of soil by breaking down leaf litter into nutrients that feed plants.
Because herbicides are mobile in the soil and the roots of plants and trees are often intertwined, non-target plants are often harmed or killed.

Despite knowing that glyphosate probably causes cancer in humans and that many herbicides cause significant environmental damage, native plant advocates continue to push land managers to use toxic chemicals to kill non-native plants and trees. They do so because herbicides are the cheapest method of eradicating vegetation. They do not have the person-power to eradicate all the vegetation that is being killed by herbicides. Using herbicides enables native plant advocates to claim larger areas of parkland and open space than they would be able to without using herbicides.

(1) Montellano, et.al., “Mind the microbes: below-ground effects of herbicides used for managing invasive plants,” Dispatch, newsletter of California Invasive Plant Council, Winter-Spring 2019-2020.

Nativism in the Natural World

Invasion biology is the scientific discipline that spawned the native plant movement. Charles Elton published a book in 1958 that is considered the origin of the modern version of invasion biology, although there are precursors centuries earlier. These are the basic tenets of modern invasion biology:

Plants and animals that are “native” to a specific location are considered members of an ideal ecosystem that have co-evolved over thousands of years so that members of the community are dependent upon one another.
Plants and animals introduced to an ecosystem by humans are assumed to disrupt the equilibrium balance of the community and threaten its existence because introduced plants and animals do not have predators that would control their spread. All introduced plants and animals are therefore considered potentially invasive.
Animals are believed to be dependent upon the plants with which they evolved—and only these plants–and these mutually exclusive relationships are disturbed by the introduction of new plants and animals.
Adaptation and evolution of introduced plants and animals is believed to be too slow for introduced plants and animals to successfully enter the food web.
Native members of the ecosystem are presumed to be inherently superior to introduced plants and animals. Invasion biology does not acknowledge that introduced plants and animals are often functional members of the ecological community.
Native ecosystems are said to be in “balance” and introduced species are presumed to cause “imbalance.” Introduced species must be eradicated to restore balance to the ecosystem, presumed to be the ideal for a particular location.

Hundreds of empirical studies have been conducted since the 1960s to test these assumptions. Little scientific evidence has been found to support them. Current knowledge of ecology explains why the assumptions of invasion biology are mistaken.

What is native?

The native plant movement defines native as the plant species that lived in a specific location prior to the arrival of Europeans. In the San Francisco Bay Area, “native” is defined by native plant advocates as the plants and animals that lived here prior to 1769 when Europeans first laid eyes on San Francisco Bay. When Europeans arrived, the San Francisco Bay Area was already occupied by indigenous people who had arrived approximately 10,000 years earlier.

The arbitrary selection of the pre-European settlement period to define the ideal landscape was based on the mistaken assumption that the indigenous human population had not radically altered the land. Anthropological and paleontological research informs us that the landscape was essentially gardened by the indigenous population to provide food and cultural implements.

Pomo gathering seeds, 1924. Smithsonian photo archive

The landscape found by Europeans at the end of the 18^th century was not “natural.” It was altered by humans to serve humans who lived as hunters and gatherers. Since modern society no longer hunts and gathers for its food and shelter, the landscape that served that lifestyle cannot be maintained without mimicking the land management practices of native people such as frequent burning of the landscape and grazing by animals. Indigenous people in California did not have domesticated animals (except dogs), but the grassland was grazed by wild deer, elk, and antelope.

Plants and animals have migrated around the world without the assistance of humans since life began. The seeds of plants are carried in the stomachs of migrating birds and on the winds of storms. Animals, including humans, move to wherever they can find what they need to survive. Migration is natural and often necessary for survival. Making a distinction between species moved by humans and those moved by natural forces is pointless and usually impossible to distinguish.

Climate change renders the concept of “native plants” meaningless because when the climate changes, the vegetation changes. The plants that live in tropical climates will not survive in arctic cold and vice versa. Introduced plants are often better adapted to current climate conditions than their native predecessors because the climate has changed and it will continue to change.

Mistaken assumptions about evolution

Animals rarely depend upon a single plant species for survival. Such mutually exclusive relationships rarely exist in nature because they are evolutionary dead-ends. Animals can, and often do, adapt quickly to changes in the environment. Transitions from native to introduced plants are routinely made by animals, including humans. Indigenous hunter/gatherers quickly incorporated plants introduced by European settlers into their diets. Plants in the same family and genus are often chemically similar, making the transition more likely.

Native plant advocates assume that evolution only occurs slowly, over thousands of years, but evolution can be faster than they assume. Rapid environmental change accelerates the speed of evolution because extreme weather events caused by climate change increase the speed of natural selection, the primary tool of evolution. When cataclysmic events such as hurricanes, droughts, floods, extreme temperatures kill many members of a species population, these are selection events in which the fittest members survive to breed and the next generation inherits the genetic traits that helped their parents survive. The classic example of this principle is the finches in the Galapagos Islands who died if they didn’t have big enough beaks to eat the seeds of the only plant that survived extreme drought. The next generation of finches had bigger beaks.

Darwin’s finches are an example of rapid evolution

Evolution occurs when genetic changes enable future generations to inherit the genetic change. Adaptation occurs when animals respond to environmental challenges by changing behaviors that aren’t necessarily inherited by the next generation. Adaptation to changed environmental conditions is even more rapid than evolution and equally effective to ensure survival. Genetic changes are not required for an insect to make the transition from a native host plant to a chemically similar introduced plant. Extreme temperatures require that plants and animals move to more temperate climates. “Native” ranges must change to survive changes in the environment. A plant or animal that cannot survive extreme heat will migrate (if it can) into regions where temperatures are not as warm. They should not be prevented from doing so.

Plant and animal species with large populations and short lives, such as insects, evolve more quickly. This more rapid pace of evolution enables a more rapid transition from native host plants to closely related introduced plants.

soapberry bug made transition from native to non-native balloon vine in 20-50 years. Scott Carroll, UC Davis

Nativism and the native plant movement

The native plant movement is based on the belief that native plants are superior to introduced plants, that native plants are somehow “better” than immigrant plants. That assumption of superiority is the definition of nativism. It is as specious an assumption in the natural world as it is in human society and it is equally dangerous.

There are pros and cons to everything living in the natural world and there is no right answer to the question of which species is “best.” When evaluating introduced plants, nativists consider only the negative aspects. They refuse to acknowledge that there are also advantages and a death verdict should take both into consideration. For example, native plant advocates want all eucalyptus trees in California cut down because they were planted here after European settlement. This negative judgment of eucalyptus does not take into consideration that 75% of monarch butterflies who spend the winter in California use eucalyptus trees for their safe haven. Also, eucalyptus blooms in California from November to May, providing nectar to butterflies, hummingbirds, and bees at a time of year when native plants are not blooming. Eucalyptus trees are also nesting homes of owls and other raptors. Cutting down eucalyptus trees simply because they are not native in California ignores the many benefits they provide to wildlife.

Monarch butterflies over-winter in California’s eucalyptus groves

Confusing cause and effect

The native plant movement mistakenly assumes that the mere existence of introduced plants threatens the existence of native plants. They believe that native plants will magically emerge if introduced plants are eradicated. They have spent 25 years eradicating non-native plants and do not seem to have noticed that native plants have not returned. They make this mistake because they do not acknowledge the changes in the environment that make non-native species better adapted to current environmental conditions.

Many of the changes in the environment that are inhospitable to native species are caused by structural changes made to accommodate human activities, not by introduced species. For example, all the major rivers in California have been dammed to prevent floods and store water for use during the dry season. These dams have fundamentally altered the ecology of our rivers. There are no longer cleansing spring floods that clear rivers of accumulated mud and vegetation. Channeled rivers are deeper and warmer. Salmon can no longer get to their spawning grounds past the dams. The altered structural conditions are more hospitable to bass than to trout. Aquatic plants from tropical regions become invasive in warmer water. None of these conditions are reversed by spraying aquatic plants with herbicide or killing introduced bass.

Butterfly bush (buddleia) is now being eradicated by nativists.. butterflybush.com

Wherever “invasions” are observed, no thought is given to why. Instead, a convenient plant or animal scapegoat is found and poisoned. That death sentence doesn’t reverse the underlying reason for the invasion. Therefore, the invasion persists. Society is unwilling to make the sacrifices, even inconveniences, needed to address the underlying cause of the “invasion.” We have done little to address the causes of climate change. We are unwilling to destroy the dams and the system of supplying water to serve agriculture needs. Invasions are the symptom, not the cause of the changes in nature.

Conservation Sense and Nonsense

You are receiving this announcement of our changed focus and new name because you are a subscriber to our original Million Trees blog. This is our revised mission for the Conservation Sense and Nonsense blog:

Conservation Sense and Nonsense began in 2010 as the Million Trees blog to defend urban forests in the San Francisco Bay Area that were being destroyed because they are predominantly non-native. In renaming the Million Trees blog to Conservation Sense and Nonsense, we shift the focus away from specific projects toward the science that informed our opposition to those projects.

Many ecological studies have been published in the past 20 years, but most are not readily available to the public and scientists are often talking to one another, not to the general public. We hope to help you navigate the scientific jargon so that scientific information is more accessible to you. If this information enables you to evaluate proposed “restoration” projects to decide if you can or cannot support them, so much the better.

Anise Swallowtail butterfly in non-native fennel. Courtesy urbanwildness.org

Since 2010, we have learned more about the ideology of invasion biology that spawned the native plant movement and the “restoration” industry that attempts to eradicate non-native plants and trees, usually using herbicides. We have read scores of books and studies that find little scientific evidence in support of the hypotheses of invasion biology. We have studied the dangers of pesticides and the growing body of evidence of the damage they do to the environment and all life.

Meanwhile, climate change has taken center stage as the environmental issue of our time. Climate change renders the concept of “native plants” meaningless because when the climate changes, vegetation changes. The ranges of plants and animals have changed and will continue to change to adapt to the changing climate. Attempting to freeze the landscape to an arbitrary historical standard is unrealistic because nature is dynamic. Evolution cannot be stopped, nor should it be.

Destroying healthy trees contributes to climate change by releasing stored carbon into the atmosphere. Both native and non-native trees store carbon and are therefore equally valuable to combat climate change. Native vegetation is not inherently less flammable than non-native vegetation. There are advantages and disadvantages to both native and non-native vegetation.

The forests of the Earth are storing much of the carbon that is the primary source of greenhouse gases causing climate change. Deforestation is therefore contributing to climate change. By destroying healthy trees, the native plant movement is damaging the environment and its inhabitants.

Housekeeping

All of the articles on the Million Trees blog are still available in the archive on the home page. The search box on the home page will take you to specific subjects of interest. Visit the pages listed in the sidebar of the new home page for discussion of each of the main topics by clicking on the links above. Readers who subscribed to the Million Trees blog will receive new articles posted to Conservation Sense and Nonsense unless they unsubscribe. Thank you for your readership. Your comments are welcome and will be posted unless they are abusive or repetitive.