I was encouraged to hear a presentation by an academic scientist at the recent Beyond Pesticides Forum that was another indication of the paradigm shift in invasive species management toward a less destructive approach.Dr. Bernd Blossey is a Professor at Cornell University, where he directs the Ecology and Management of Invasive Plants Program in the Department of Natural Resources. His many years of studying invasive plants, such as purple loosestrife, garlic mustard, water chestnut, Japanese knotweed, and phragmites have convinced him that there are often “multiple stressors” that contribute to such invasions. Some factors such as the presence of earthworms and deer can be more important factors in the Northeast than the non-native plants themselves.
Based on his research experience, Dr. Blossey delivered wise advice to land managers at the Beyond Pesticide Forum. The featured photo at the top of this article was his introductory slide.
Before a restoration project begins, these questions should be asked and answered:
If the project seems worthwhile after such analysis is done, this is Dr. Blossey’s advice about monitoring the project and measuring its success:
Practicing what he preaches
Dr. Blossey used these principles in his study of garlic mustard in the forests of the northeast. (1) Over a period of more than 10 years, Dr. Blossey and his collaborators measured the abundance of garlic mustard in 16 plots from New Jersey to Illinois where no attempt had been made to control or eradicate it. They found that growth rates initially increased, but decreased over time and eventually the population started to decline. Dr. Blossey explained their findings in a recent webinar that is available HERE:
Garlic mustard was first recorded in North America in 1868 on Long Island, New York. It spread west from there and is now found from southern Canada to Georgia and from New York and Quebec to Oregon, British Columbia and Alaska. Because land managers believed that garlic mustard suppresses populations of native plants, they have been trying to eradicate garlic mustard in northern forests for decades, with little long term success. Dr. Blossey addressed that concern in his webinar.
Earthworms are the prerequisite for garlic mustard invasion. Earthworms in northern forests are also considered alien invaders because they were killed, along with forests, by advancing glaciers during the Ice Age. When forests returned after the Ice Age over 10,000 years ago, they evolved without earthworms that were reintroduced by European settlers less than 500 years ago.
When deer are excluded from areas by fencing plots with garlic mustard populations, abundance of native vegetation does not decline. Deer have a strong preference for native vegetation. Absent deer, garlic mustard does not seem to suppress the growth of native plants in northern forests.
In other words, garlic mustard is not guilty as charged. Dr. Blossey explains the disadvantages of attempting to eradicate it. The decline of garlic mustard abundance over time is attributed to negative soil feedback that builds over time as the soil microbial community responds to the new plant. Removing garlic mustard episodically prolongs the process of building that negative soil feedback. When groups of well-meaning young people are sent into the forest to pull garlic mustard, they trample the very native plants they are trying to save.
Are there lessons for land managers in the Bay Area?
Because garlic mustard doesn’t exist in California and our native earthworms are considered beneficial to soil health, you might wonder if this study is relevant here. California was not glaciated during the Ice Age. Our earthworms survived the Ice Age and they evolved with our forests.
So, what can we learn from this study?The pattern of initial growth and eventual decline of populations of introduced plants is not unique to garlic mustard: “A phenomenon that has received increased attention is whether introduced species go through boom and bust cycles, ultimately becoming non-threatening members of local communities.” (1) One recently published study was based on nearly 5,000 vegetation inventories collected in 49 National Parks in the eastern United States. It reported that non-native plants appeared to decline after 100-200 years:
“Residence time appears a core part of invasion that interacts with other mechanisms, such as climate matching, propagule pressure and empty niche. Initially, time appears to benefit non-native species as they establish in a novel range. They likely face low enemy loads, and any successful dispersal increases their populations and invaded range. As they spread, initial barriers, such as distance or suboptimal habitat, were overcome, as was resistance from native relatives. However, their biggest challenge appeared to be time, as they all declined after ~1 to 2 centuries, suggesting that pathogens and herbivores caught up with them.” (2)
The message for land managers everywhere is that patience is needed to judge the impact of introduced species. Most will fit into ecosystems eventually and attempts to speed up that process often do more harm than good. We can’t judge changes in nature by the short-term perspective of human lifetimes because the evolution of nature is a continual process that began long before humans existed and is likely to persist long after we are gone.
Applying Dr. Blossey’s “Core Knowledge” to local projects
What if Dr. Blossey’s “Core Knowledge” had been applied to projects in the San Francisco Bay Area? Here are examples of local eradication projects that might have benefitted:
San Francisco has been trying to eradicate oxalis in its parks for over 20 years by spraying a selective herbicide (Garlon). There seems to be more oxalis now than there was 20 years ago. Oxalis is visible only about 2 months of the year. When it dies back in the spring it leaves behind the native plants with which it co-exists. If a control plot had been set aside before they started eradicating oxalis perhaps we would know the answer to these important questions: Does oxalis suppress the growth of native plants? Does attempting to eradicate oxalis produce more or less oxalis?
California, Oregon, and Washington have been trying to eradicate non-native spartina marsh grass along the entire West Coast for over 20 years. Here in the Bay Area, non-native species of spartina have been 99% eradicated, but a hybrid of the native and the non-native remains and is poisoned with imazapyr annually. According to a recent presentation by the Invasive Spartina Project, the hybrid is visually indistinguishable from the native and it occupies the same elevation of the marsh. Over 500 genetic tests are needed every year to distinguish the hybrid from the native in order to poison the hybrid. Dr. Blossey’s approach might ask these important questions: What harm is hybrid spartina doing? Do more or fewer animals live in hybrid spartina? What effect has 20 years of spraying imazapyr had on the soil and the microbes that live in it? Is the eradication project doing more harm than good?
We don’t know the answers to these important questions because projects were initiated and implemented without the analysis and monitoring metrics needed to answer the questions. The projects continue without being accountable for the damage they are doing. Public money is funding these projects without requiring the projects to be accountable for the consequences.
California has made a commitment to spend billions of dollars on “nature based solutions” and achieving “biodiversity goals.” This is an opportunity to start new projects off on the right foot by:
Requiring the analysis needed to determine the impacts and causes of perceived problems in the environment.
Requiring control plots so that the effects of the project can be compared with the option of not doing the project.
Requiring that projects be monitored, using established metrics so that the success of the project can be measured.
The Million Trees blog is folding its tent and moving on because most of the projects in the San Francisco Bay Area that I have followed for 20 years have been approved, funded, and are being implemented. Every public land manager in the Bay Area has made a commitment to destroying most non-native trees and using pesticides for that purpose.
If I return to the blogosphere in the future, the title and mission of a new blog would change. The focus would be the science that informs my commitment to the cosmopolitan landscape that exists, rather than the fantasized landscape of the past. I will also continue to inform readers of new studies that find evidence of the damage that pesticides do to the environment and its inhabitants. If you are a subscriber to the Million Trees blog, you will be informed if I publish a new blog.
The California Invasive Plant Council held their 27th annual conference in Monterey in November. It was their biggest conference, with about 400 attendees and more sponsors than ever before. Clearly the industry that promotes the eradication of non-native plants is alive and well. However, a closer look at the conference presentations suggests otherwise. Eradication efforts are growing, but eradication success is not and establishing a native landscape after eradication is proving elusive.
A few common themes emerged from the presentations:
Eradication cannot be accomplished without using pesticides.
When eradication is achieved with pesticides, non-natives are rarely replaced by native plants.
Planting natives after non-natives are eradicated reduces re-invasion, but secondary invasions of different non-native plants are common.
“Managing” forests with prescribed burns did not result in more biodiversity than leaving the forest alone.
Goals of these eradication projects have shifted in response to these failures to achieve original goals:
Replacement plantings after eradication are sometimes a mix of natives and non-natives.
Inability to establish native grassland has given way to different goals.
Language used to describe the projects are evolving to be more appealing to potential volunteers.
Here are a few examples of presentations that illustrate these themes:
Eradicating beach grass in Point Reyes National Seashore
About 60% of sand dunes in the Point Reyes National Seashore were covered in European beach grass when the eradication effort began in 2000. The goal of the project was to restore native dune plants and increase the population of endangered snowy plovers that nest on bare sand.
The project began by manually pulling beach grass from 30 acres of dunes at Abbott’s Lagoon. The grass grew back within one year, presumably because the roots of the beach grass are about 10 feet long. Manually pulling the grass from the surface does not destroy the roots.
A new method was devised that was more successful with respect to eradicating the beach grass. The grass and its roots were plowed up by bulldozers and buried deep in the sand. The cost of that method was prohibitively expensive at $25,000 to $30,000 per acre and the barren sand caused other problems.
The barren dunes were mobile in the wind. Sand blew into adjacent ranches and residential areas, causing neighbors of the park to object to the project. The sand also encroached into areas where there were native plants, burying them. The bare sand was eventually colonized by “secondary invaders.” Different non-native plants replaced the beach grass because they were more competitive than the desired native plants.
In 2011, the National Park Services adopted a third strategy for converting beach grass to native dune plants. They sprayed the beach grass with a mixture of glyphosate and imazapyr. At $2,500 to $3,000 per acre, this eradication method was significantly cheaper than the mechanical method.
However, it resulted in different problems that prevented the establishment of native dune plants. The poisoned thatch of dead beach grass was a physical barrier to successful seed germination and establishment of a new landscape. Where secondary invaders were capable of penetrating the dead thatch, the resulting vegetation does not resemble native dunes.
The concluding slides of this presentation were stunning. They said it is a “Restoration fallacy that killing an invader will result in native vegetation.” My 20 years of watching these futile efforts confirm this reality. However, I never expected to hear that said by someone actually engaged in this effort. The presenter mused that such projects are like Sisyphus trying to roll a boulder up hill.
Attempting to plant Douglas fir after eradication of broom
Over a period of 5.5 years, broom was eradicated in plots in Oregon by spraying glyphosate. The plots were then planted with Douglas fir seedlings that soon died. They were replanted the following year and died in the second year.
There were two theories about why the plantings failed, both broadly described as “legacy” effects in the soil left by the broom. One theory is that nitrogen levels were too high for successful growth of Douglas fir. That theory is consistent with the fact that broom is a nitrogen fixer. That is, broom—like all legumes—have the ability to transfer nitrogen in the atmosphere to nitrogen in the soil with the help of bacteria that facilitate that transfer. Nitrogen generally benefits plant growth, but there can also be too much nitrogen.
The second theory is that Douglas fir requires a specific suite of mycorrhizal fungi for successful growth. Mycorrhizal fungi live in roots of plants and trees. They transfer moisture and nutrients from the soil to the plants. Plants with a healthy suite of mycorrhizal fungi are more drought tolerant because they extract more moisture from the soil.
Neither of these theories has been successfully proven by this project. They remain unanswered questions. We were struck that the researchers had not considered the possibility that the repeated use of glyphosate could have been a factor in the failure of the Douglas fir. Glyphosate is known to kill bacteria in the soil. Could it also kill mycorrhizal fungi? (We know that triclopyr kills mycorrhizal fungi.) That possibility was not considered by this project. Did the project consider that glyphosate also changes the consistency of the soil by binding certain minerals together? It is more difficult for roots and water to penetrate the hard soil. Were soil samples taken before and after repeated applications of glyphosate to determine how the soil had been changed by pesticide applications?
The published abstract for this project made this observation: “It is typically assumed that once an invasive species is successfully removed, the impact of that species on the community is also eliminated. However, invasive species may change the environment in ways that persist, as legacy effects, long after the species itself is gone.” In fact, it seems likely that the pesticides used to eradicate the “invasive” species could also be the source of the “legacy effects.”
Does “managing” a forest result in greater biodiversity in the understory?
California State Parks tested that hypothesis by conducting prescribed burns in some of their forests in the Sierra Nevada 20 years ago, while leaving other portions of the forest “unmanaged.”
The abstract for this presentation describes the goals and expectations for the prescribed burns: “Prescribed fire is a tool used to reduce fuels in the forests in the Sierra Nevada and mimic the low and moderate severity wildfires that burned before the onset of fire suppression. A manager’s hope is that prescribed fire will create the disturbance necessary to stimulate the development of species rich understory communities and increase species richness, compared to unburned forests, which are often viewed as species depauperate.”
Twenty years after the burns, abundance and species composition of the understory in the burned areas were compared to the unburned areas. They found little difference in the biodiversity of the understory of burned areas compared to unmanaged forests:
“Species richness was highly variable within burned and passively managed areas but was not statistically different.”
“Passively managed areas did not appear to be depauperate in understory species diversity compared to areas managed with prescribed fire.”
“Fire did not appear to reduce or enhance species richness numbers in burned areas, as compared to passively managed areas.”
No fires occurred in either the burned areas or the unmanaged areas during the 20-year period. Therefore, this study did not test the theory that prescribed burning reduces fire hazards in forests. This study found no significant differences in diversity of forest understory resulting from prescribed burns.
There are significant risks associated with prescribed burns. They cause air pollution and they frequently escape the controlled perimeter of the fire, becoming wildfires that destroy far more than intended. This study does not provide evidence that would justify taking those risks. In fact, available evidence supports the “leave-it-alone” approach to land management.
Moving the goal posts
If at first you don’t succeed, you have the option of redefining success. Here are a few of the projects presented at the conference that seemed to take that approach.
Make projects so small that success can be achieved
Eric Wrubel introduced himself as the National Park Service staff who is responsible for prioritizing invasive plants for removal in the National Parks in the Bay Area (GGNRA, PRNS, Muir Woods, and Pinnacles). His work is based on the premise that the most successful eradications are those that are small. The bigger the infestation, the greater the investment of time and resources it takes to eradicate it and the smaller the likelihood of success. This is illustrated by a graph showing this inverse relationship between the size of the invasive population and the success of eradication.
The process of prioritizing eradication projects began over 10 years ago with a survey of over 100 species of plants considered invasive. Cal-IPC’s “watch list” was used to identify the plants that are not yet widely spread in California, but considered a potential problem in the future. Cal-IPC’s risk assessment was the third element in the analysis. Plants with “High” risk ratings by Cal-IPC were put higher on the priority list than those with “Moderate” or “Limited” ratings. Plants that did not exist elsewhere in the region or watershed were also given higher priority, based on the assumption that re-invasion was less likely.
The priority list showed that the highest priority eradication projects were quite small. Some were just a few acres. Buddleia jumped out as the 7th highest priority on only 13 acres. Buddleia was recently added to a new category of plants on Cal-IPC’s “invasive” inventory. It is not considered invasive in California, although it is considered invasive elsewhere.
In placing buddleia on its “hit list,” Cal-IPC illustrates one of the fundamental weaknesses of its evaluation method. Cal-IPC does not evaluate pros and cons of non-native plants. Only traits considered negative are taken into consideration.
Buddleia is one of the most useful nectar plants for pollinators in California. We took the time to visit the monarch butterfly sanctuary in Monterey while attending the conference. The monarchs are arriving now to begin their winter roost in the eucalyptus, Monterey pine and cypress in this small grove. At the entrance to the sanctuary a sign instructs visitors to plant only native milkweed as the monarch’s host plant and only native flowers for nectar. Fortunately whoever planted the flowering shrubs in the sanctuary didn’t follow the advice of the sign-makers. They planted buddleia and other flowering non-natives such as bottle-brush. Several species of butterflies and hummingbirds were enjoying those plants in the Sanctuary. Strict adherence to the native plant agenda is not beneficial to wildlife because animals do not share our prejudices.
Acknowledging the difficulties of converting non-native annual grass to native perennial grass
Pinnacles National Park acquired 2000 acres of former ranchland in 2006. The park wanted to convert the non-native annual grasses and yellow-star thistle on the former ranch to perennial bunch grasses and oak woodland. They were able to reduce the amount of yellow-star thistle by burning and spraying with herbicide, but cover of native species remained low. Conversion of grasses from non-native annuals to native perennial grass has been tried many times, in many places, and for long periods of time. These projects were notoriously unsuccessful.
The project at Pinnacles has changed its goal to plant forbs (herbaceous flower plants) instead of grasses and they report that they are having some success. They justify that shift in goal on soil analysis that suggests forbs were more prevalent than perennial grasses in inland valleys in California than previously thought.
This change in goal could be described as “adaptive management,” which adjusts methods and goals in response to observable outcomes of existing methods. You could also call it “trial and error.” We would like to see more land managers make such adjustments to their strategies, rather than doing the same thing over and over again and expecting a different outcome.
Recruiting volunteers with appealing messages
There were several presentations about effective methods of recruiting volunteers to participate in restoration projects. Some of their messages seem to acknowledge that the language used in the past may have alienated some potential volunteers. Speaking from personal experience, I can confirm that observation. Here are just a few of the cringe-worthy native plant mottos that I hope have been abandoned in favor of a more positive message:
“That plant doesn’t belong here.”
“That is a good plant and the other is a bad plant.”
“The invasive landscape is sick and requires chemotherapy.” (to justify the use of pesticides)
“That’s a trash bird.” (said of common, introduced birds, such as starlings and house sparrows)
The speaker advised those who work with volunteers to focus on why an unwanted plant is a problem rather than where it comes from. Unfortunately, the list of problems is heavily influenced by the preferences of native plant advocates. If their criticisms are not accurate, or they don’t acknowledge the advantages of the plant, little has been achieved by using euphemisms. Here are a few of the inaccurate criticisms made of eucalyptus:
“Eucalyptus kills birds.” This was one of the most ridiculous accusations, but is still occasionally heard among native plant advocates.
“Eucalyptus is very invasive.” Cal-IPC rates invasiveness of eucalyptus as “Limited.” They spread only when planted beside streams or swales that carry their seeds downstream and in very foggy coastal locations with a lot of wind to carry the seeds.
What was missing?
Ecological restoration is a major industry. Thousands of people are employed by the industry, which is funded by many different sources of public money. Whether individual projects are successful or not, the industry will survive and thrive as long as it is funded. Greater care should be taken to design and implement projects that will be successful.
Stepping back from the conference presentations of specific restoration projects, here are a few issues that were conspicuously absent from the conference.
Pesticides are being widely used by the restoration industry. When projects don’t achieve desired outcomes, pesticides should be considered as a factor. Did pesticides alter the soil? Were beneficial microbes and fungi killed? How persistent was the pesticide in the soil? How mobile was the pesticide in the soil? Was pesticide applied in the right manner? Could aerial drift account for death of non-target plants? There are many other useful questions that could be asked.
Update:The California Invasive Plant Council has published “Land Manager’s Guide to Developing an Invasive Plant Management Plan.” It says very little about the disadvantages of using herbicides to eradicate plants they consider “invasive” other than a vague reference to “unintended consequences,” without discussion of what they are or how to avoid them.
However, it does give us another clue about why eradication efforts are often unsuccessful. When herbicides are used repeatedly, as they have been in the past 20 years, weeds develop resistance to them: “The International Survey of Herbicide Resistant Weeds (2018) reports there are currently 496 unique cases (species x site of action) of herbicide-resistant weeds globally, with 255 species…Further, weeds have evolved resistance to 23 of the 26 known herbicide sites of action and to 163 different herbicides.” The Guide therefore recommends that land managers rotate herbicides so that the “invasive” plants do not develop resistance to any particular herbicide. The Guide gives only generic advice to use “herbicide X” initially and “herbicide Y or Z” for subsequent applications.
In other words, the California Invasive Plant Council continues to promote the use of herbicides to kill plants they consider “invasive.” They give advice about ensuring the effectiveness of herbicides, but they do not give advice about how to avoid damaging the soil, killing insects, and harming the health of the public and the workers who apply the herbicides. May 20, 2019
Are workers who apply pesticides being adequately trained and supervised by certified applicators? The safety of workers should be one of many goals of restoration projects.
When non-native plants are eradicated, serious thought should be given in advance to the probable outcome. Will native plants return? Will wildlife be harmed? Will the risks of failure outweigh the potential benefits of success?
Is climate change taken into consideration when planning the replacement landscape? Are the plants that grew in the project location 200 years ago still adapted to that location? Is there enough available water?
If new plantings require irrigation to be established, what is the water source? Is it recycled water with high salt content that will kill many plants, including redwoods?
Does the project team have sufficient horticultural knowledge to choose plants that can survive in current conditions? Does the project team know the horticultural needs of the plants they are planting? Is there enough sunlight, water and wind protection for the trees they are planting?
The public is investing heavily in the “restoration” of ecosystems. We can only hope that our investment is being used wisely and that projects will not do more harm than good. Cal-IPC can play a role in raising the questions that have the potential to improve projects and enable them to succeed. The long-term survival of the “restoration” industry depends on it.
Most quotes are from abstracts of presentations published in the conference program.
Catalina Island is dear to my heart because of several childhood vacations there. It was thrilling to return after 60 years and find it unchanged from my memories. Avalon, the small town of about 3,500 people, is still a quaint collection of little wooden shacks, painted bright colors. But as an adult, my recent visit to Catalina was broader and encompassed the entire island, which was unknown to me as a child. That broader perspective on Catalina is my focus today. (1)
Catalina is one of the Channel Islands off the coast of Southern California. It rose from the ocean about 5 million years ago as the result of geologic processes lifting the ocean floor as tectonic plates collided. Like other oceanic islands (as opposed to those that broke off from continents), it was composed of barren rock for thousands of years. It took thousands of years to build soil needed to support plants. Then it took thousands of years to establish plants from the seeds blown in the wind from the mainland, brought by birds in their stomachs or adhered to their feathers and feet, or brought by waves carrying plants in storms. When plants gained a foothold, the island was able to support insects brought by wind and waves.
The process of populating Catalina with plants and animals accelerated with the arrival of American Indians about 10,000 years ago. Foxes were probably brought to Catalina by the Indians and oaks probably arrived as acorns brought by the Indians. Archaeological remains of Indian settlements indicate that there were as many as 2,500 Indians living on Catalina, using only the food and materials available on the island or the surrounding ocean.
Most of the plant and animal life on Catalina came from the mainland of California, only 22 miles away from the island. When plants and animals evolve in isolation from their ancestors, their gene pools gradually drift apart and are eventually distinct species. That’s why there are about 60 plant and animal species on Catalina that are endemic, meaning that they exist only on Catalina. This process of diverging evolution from mainland ancestors to unique island species is typical of all island ecosystems.
Europeans arrive on Catalina
Catalina was visited by Spanish explorers for the first time in 1542 and again in 1602. Although their visit was brief, it was fatal because they brought diseases to which Europeans were immune and the Indians were not. Most of the Indians on the island were killed by those diseases, a scenario that played out all over the New World in the 16th and 17th centuries.
Europeans tried to establish communities on the island in the 19th century, but their economic ventures were not successful. They brought sheep, cattle and goats. But there wasn’t sufficient forage for their herds and supplementing their diets by growing hay wasn’t economically viable. They tried mining, but found little of value. They introduced animals for hunting, such as mule deer and pigs.
Towards the end of the 19th century, Europeans made their first attempt to turn the island into a tourist destination. The first effort ended when the entire town of Avalon burned in a fire in 1915. That fire set the stage for the final chapter in the development of the island. William Wrigley Jr. was able to purchase the entire island in 1919 in the “fire sale” that resulted in a bargain price.
The Wrigley Era on Catalina
William Wrigley Jr. made his fortune manufacturing and selling chewing gum. He had the means to indulge his passion for the island, which he envisioned as a recreational paradise. He built a magnificent Art Deco casino in Avalon that opened in 1929 and turned the town of Avalon into a famous destination that attracted celebrities as well as one million visitors each year, arriving on the huge steamers Wrigley built to bring them to Catalina.
Many movies were made on Catalina and movie stars were frequent visitors to the island. One of the movies brought bison to the island to feature in their western themed story. The bison herd grew and eventually became another challenge to the survival of vegetation on the island.
The conservancy era on Catalina
When William Wrigley died, his heirs changed the direction of the island’s development. The island could have continued to grow into a tourist destination, but in 1972 Wrigley’s heirs decided that nearly 90% of the island would be turned into a nature reserve. The Catalina Island Conservancy was born. Access and development on conservancy land is restricted.
The conservancy has made big investments in restoring the island’s ecosystems and protecting endemic plant and animal species. Sheep and cattle were removed, which wasn’t difficult because those enterprises had largely failed. Feral pigs and goats were much harder to round up and were killed by hired sharp shooters. The extermination of the pigs and goats was as controversial on Catalina as it has been on other Channel Islands. A decade later, “with the quality of the island habitat rebounding and increased ecotourism revenue being realized by island businesses, the bitterness surrounding the pig and goat eradication is subsiding.Conservation, contrary to popular belief, is not one long group hug. This stuff can be hard.” (1) Indeed, “restorations” in the San Francisco Bay Area have caused one pitched battle after another for over 20 years. They might have been less heated battles if all opinions had been treated with equal respect, as they seem to have been on Catalina Island.
The population of mule deer is being controlled with hunting licenses. Most of the herd of 600 bison was given to an Indian reservation in South Dakota. The remaining herd of 150 is being controlled by a contraception program. Maintaining the small bison herd is considered a concession to their popularity with residents and tourists on the island.
The Catalina Island Fox, an endemic species, was nearly wiped out by distemper virus introduced by a castaway raccoon. Fortunately, conservancy staff figured out why the population dwindled to only 100 foxes in time to save the foxes from extinction. A captive breeding and vaccination program returned the fox population to over 1,500 animals in 2011. A captive breeding program for the island’s bald eagles has also restored their population.
Like most restorations, the Catalina Island Conservancy is concerned about invasive species. However, their approach to controlling non-native plants is less extreme than many similar projects. They consider a species of broom (Genista linifolia) their highest priority for eradication. Although they have tried and will continue trying to control it they acknowledge that it may not be possible.
Genista linifolia is native to the Canary Islands. It was introduced to Catalina over 100 years ago when it was used to landscape the Saint Catherine Hotel when it was originally built in 1900. The conservancy launched the Avalon Grasses Initiative in 2016 to prevent similar introductions of grasses that have a high potential to spread on the wind—such as pampas and fountain grass–from gardens in Avalon to conservancy wildlands. Conservancy staff quietly patrol the gardens in Avalon, looking for these exotic grasses. When they find them they approach the property owner with their proposal to remove them and replace them with native plants. The 20 property owners who have agreed to this proposal express satisfaction with the substitution. This strategy seems to treat the property owners with respect. (2)
Over 200 species of non-native plants live on the island, but the conservancy considers only 35 of the species a problem. They describe their approach to non-native plants:
“The Catalina Island Conservancy has developed a thoughtful and comprehensive set of strategies for dealing with invasive plants. First, they realized that not all introduced plants are invasive and some are less likely to outcompete native species. Those considered invasive were ranked according to the magnitude of the problems they present, including how widespread they are, how fast they can spread and how damaging to the local native species they are. On the basis of this information, each highly ranked invasive species is being treated with the purpose of reducing its impact on the native communities, reducing its spread or eliminating the threat.” (1)
They acknowledge that “topical chemical treatments” are one of the methods they use to control plants they consider invasive, but details of their pesticide use are not available to me. The conservancy is a private entity that is not subject to public record laws.
My eucalyptus litmus test
There are few species of native trees on Catalina Island and their population on the island is also very small. Therefore, most trees on the island were introduced. Eucalyptus (mostly Red River gum and blue gum) were introduced to the island in the 1920s by the Wrigley family for a variety of reasons: aesthetic, shade, wind break, erosion control of road cuts, etc. Eucalypts are still there and they are the predominant tree species on the island. Eucalyptus is found throughout the island, including the town of Avalon and several places on conservancy land, where they were planted.
The conservancy does not plan to eradicate eucalyptus on the island: “The eucalyptus trees…are non-native, but are not highly invasive. Because of their non-invasive growth pattern and their place in the cultural heritage of the Island, they are not targeted for replacement, except when they die of natural causes.” (3)
I have been studying native plant restorations for over 20 years. I have finally found on Catalina a restoration that makes some sense to me.The restoration on Catalina Island has been more constructive than it is destructive. It has killed less and preserved more. It preserves eucalyptus because they aren’t doing any harm. It does not fabricate a cover story to justify killing eucalypts just because they aren’t native.
The conservancy also acknowledges that difficult choices must be made and that differing opinions must be respected. Recreational interests and aesthetic preferences are not always consistent with the goals of conservation. The conservancy preserves bison because people like to see them, despite the fact that they are not native to the island. Competing interests must be balanced if the restoration is to be supported by residents of the island: “We have realized that people are an intrinsic part of the nature of the island—an influential and fundamental component of the conservation effort.” (1)
Most of this article comes from this book (1) which was written by the leadership of the Catalina Island Conservancy:
Frank Hein & Carlos de la Rosa, Wild Catalina Island: Natural Secrets and Ecological Triumphs, Natural History Press, 2013
“Protecting Catalina’s Wildlands from Invasive Plants,” Catalina Island Conservancy Times, Fall 2017
In 2004, voters in Alameda and Contra Costa counties approved Measure CC, a parcel tax, to provide additional funding to East Bay Regional Park District for “Park Access, Infrastructure and Safety Improvements, Resource-Related Projects, and Reserve for Unknown Events.” Measure CC also stipulated that “the overall commitment to natural resources shall be no less than 30% of the revenue raised by the entire measure.” (1) Measure CC is projected to provide about $47 million in the 15 years of its life. (2)
The park district is planning to put Measure CC on the ballot for renewal next year. It’s time to look at how the park district spent our tax dollars and decide if we want to continue to give them our tax dollars for another 15 years. If you want Measure CC funding to be used differently, now is the time to tell East Bay Regional Park District what you want…BEFORE the ballot measure is written.
Fuels Management vs. Resource Management?
The park district budgeted $10.2 million of Measure CC funding for “fuels management,” about 22% of the total available funding from Measure CC. To date, the park district has appropriated $8.8 million of that budget allocation and spent $6.3 million.
The park district describes “fuels management:”“All vegetation/fuels management projects for fuels reduction are in coordination with the protection and enhancement of wildlife habitat in fuel break areas and are therefore considered to be resource related.” (2) In other words, the park district considers destroying vegetation and cutting down trees a part of its “commitment to natural resources.”
These descriptions of Measure CC projects illustrate the close relationship between fuels management and resource management:
“Assess and remove hazardous trees, promote native tree regeneration.” (2)
“Manage exotic plant species and promote fire resistant natives to reduce the risk of wildfires.” (2)
“Manage vegetation for fuels reduction in coordination with the protection and enhancement of wildlife habitat in fuel break areas to provide defensible space and meet Hills Emergency Forum flame length standard.” (2)
The park district’s policies and practices are based on mistaken assumptions:
There is a wide range of opinions about the tree removals that the park district has done since their program began in 2011, after approval of the “Wildfire Hazard Reduction and Resource Management Plan” and the associated Environmental Impact Report. At one extreme, some people want the park district to destroy ALL non-native trees on its property. They consider “thinning” inadequate. The Sierra Club is in that camp and has sued to enforce their wishes. At the other extreme, some people don’t want any trees to be removed, although most would make an exception for dead and hazardous trees.
After observing the park district’s tree removal projects, I have reached the conclusion that they represent a middle ground that I can accept because in many cases the canopy is intact and the forest floor is still shaded. The shade retains the moisture that retards fire ignition as well as suppresses the growth of weeds that ignite more easily during the dry season. In the 20+ years that I have defended our urban forest, I was always willing to accept a compromise and the park district’s methods look like a compromise to me. I still have concerns about tree removals and they are explained HERE. You must reach your own conclusions.
So, what’s the beef?
Unfortunately, coming to terms with the park district’s tree removals has not resolved my misgivings about how Measure CC money has been used. In a nutshell, I believe that the park district’s “resource management” projects are based on outdated conservation practices. I believe the park district is trying to re-create historic landscapes that are no longer adapted to environmental conditions. Their projects are often not successful because they do not take the reality of climate change into consideration, nor do they look to the future of our environment. They are stuck in the past.
One of the projects funded by Measure CC is typical: the effort to eradicate non-native spartina marsh grass from all park properties. The park district has been participating in the effort to eradicate all non-native spartina marsh grass from the entire West Coast for 14 years. In the first few years, EBPRD aerial sprayed from helicopters several hundred gallons of herbicide per year. Now the quantity of herbicide is about 25 gallons per year.
The reason why the rails have been harmed by the eradication of their habitat is that non-native spartina provides superior cover for the rail. The non-native species of spartina grows taller, more densely, and it doesn’t die back in the winter as the native species of spartina does. When the rail begins its nesting season, there is no cover for the birds. They are therefore being killed by their many predators.
The fact that non-native spartina provides superior cover for the birds is related to a second issue. Non-native spartina provides superior protection from winter storm surges compared to the native species which provides no protection, even when it grows and it is NOT growing.
The third issue is that eradicating non-native spartina has not resulted in the return of native spartina. Even when extensive planting has been done, native spartina does not provide habitat or storm surge protection in the San Francisco Bay Area. We should be asking if pouring hundreds of gallons of herbicide on the ground might be a factor in the unsuccessful attempt to bring native spartina back to the Bay Area.
Finally, recently published studies that compared native with non-native marsh grasses and aquatic plants with respect to the ecological functions they perform. These studies both say, “If you look at the role of exotic water plants in an ecosystem, you won’t find any significant differences compared to indigenous species.”
The spartina eradication project is an example of conservation that no longer makes sense. It damages the environment with herbicides. It destroys the habitat of rare birds. It exposes our shoreline to strong storm surges and rising sea levels. Native vegetation does not return when it is eradicated.
Looking forward, not back
The parks are very important to me. I visit them often and I treasure those visits. I would like to vote for Measure CC. I hope that the measure on the ballot will give me a reason to vote for it.
I will be looking for a revised definition of “resource management” in the ballot measure, one that acknowledges that climate change is the environmental issue of our time and that conservation must be consistent with the changes that have already occurred, as well as look forward to the changes that are anticipated in the future. Specifically, “resource management” must respect the landscape we have now, which means not trying to eradicate it, particularly by spraying it with herbicides. Resource management projects must be based on reality, rather than on fantasies about the past.
Opportunities to tell EBRPD what you want from Measure CC
East Bay Regional Park District is holding public meetings about Measure CC to give the public the opportunity to provide input regarding future park needs and priorities:
November 4, 10-12, Harrison Recreation Center, 1450 High St, Alameda
November 8, 2:30-4:30 pm, David Wendel Conference Center, 1111 Broadway, 19th Floor, Oakland
EBRPD asks that the public RSVP by sending an email to Monique Salas at email@example.com or call 510-544-2008.
If you can’t attend, please send written feedback here: firstname.lastname@example.org. Please tell East Bay Regional Park District what you want Measure CC funding to pay for.
We are publishing a “progress report” from a member of our tree team who attended a Weed Management Workshop on June 3, 2017. This report suggests that the goal of local ecological “restorations” may be more realistic than they were in the past and potentially less destructive.
I attended a Weed Management Workshop this morning that was co-sponsored by East Bay Regional Park District and the California Invasive Plant Council. It was attended by about 70 people, representing many of the “stewardship” organizations engaged in native plant “restorations.” The main speakers were Doug Johnson, Executive Director of the California Invasive Plant Council and Pam Beitz, a member of the Integrated Pest Management staff of the East Bay Regional Park District.
The primary purpose of the workshop was to recruit new volunteers for the many “restoration” projects in the East Bay. Similar workshops will be offered in Mill Valley (June 17), San Jose (June 24), and Portola Valley (July 15). Since volunteers do not use pesticides or heavy equipment, those methods of eradicating “invasive” plants were not discussed. [Information about remaining workshops available HERE.]
Although the usual accusations about the negative impact of “invasive” plants were discussed, the speakers made several acknowledgements about limitations on their objectives that represent significant progress in the 25-year debate about invasion biology.
In the spirit of encouragement, I will tell you about a few of them.
Doug Johnson set the tone at the beginning of the workshop when he said, “Non-native plants aren’t evil. It’s important not to get ideological about this.” The audience did not react negatively to his appeal to base judgments about non-native plants on their ecological function and impacts on ecosystems.
Pam Beitz acknowledged that the historical landscapes, which “restorations” attempt to recreate were, in fact, manmade. She provided several observations from Kat Anderson’s Tending the Wild to illustrate that point. Native Americans intensively gardened the landscape to foster the plants they needed for food, shelter, and tools. The implication of that history of our landscape is that ecological “restoration” must make a permanent commitment to managing the landscape. [HERE is an article on Million Trees about “Tending the Wild.”]
Beitz said the goal of these weed management projects is to eliminate “invasive” plants from a small enough area that it can be managed for the long term. She said it is no longer considered feasible to eradicate “invasive” plants.
In answer to the question, “Why manage the wildlands?” Beitz said, “Because we are driven to alter our environment.” She also said that human disturbance maximizes biodiversity, citing a study by Joe Connell that found the greatest diversity where there are intermediate levels of disturbance. This is a radical departure from the earlier view that the most effective conservation eliminates all human activities.
There were also many representatives of local “restoration” projects who described their projects and recruited more volunteers. Some of their presentations indicated the shifting emphasis of native plant “restorations.”
Margot Cunningham of Friends of Albany Hill said that 50% of the 300 plants on Albany Hill are natives, despite the fact that it is heavily forested in eucalyptus, and that many of those native plants are growing under the eucalypts. She said there are 100 species of butterflies and moths and that monarchs roost in the eucalyptus trees. There are 80 species of birds. Her organization is trying to eliminate plants they consider invasive, such as ivy. [HERE is an article on the Million Trees blog about Albany Hill, which corroborates the view of Friends of Albany Hill.]
Wendy Tokuda is one of the most prominent native plant advocates in the East Bay. She described several of the projects she has been working on for about 10 years, such as trying to eliminate broom along 3 miles of a trail in EBRPD. She emphasized the importance of focusing one’s effort on a small enough area that the goal can be both attained and sustained. [HERE is an article on the Million Trees blog about the 10-year attempt to eradicate broom on a trail in the East Bay Regional Park District.]
Friends of Five Creeks said, “In a city, stewardship is forever.”
I have been following the native plant movement for over 20 years. I believe this workshop articulated some significant departures from their original agenda:
There is a new understanding that the historical landscape was created by humans.
Any attempt to recreate the historic landscape will require a permanent commitment to manage the landscape.
Because of the scale of such an undertaking, it is not realistic to transform all open space to pre-settlement conditions. Projects must be scaled to match available resources.
Anonymous member of the tree team
The observation that humans are “driven to alter our environment” struck a chord. We are in the camp that prefers not to interfere with the workings of nature any more than necessary because we believe that human knowledge is inadequate to presume to make better management decisions than natural processes. There are pros and cons to every change in nature. Some plant and animal species will benefit and some will be harmed. It’s like flipping a coin. I prefer to put the coin in the hands of nature, rather than the hands of humans. However, we understand and are sympathetic to the human desire to “help” nature.
A recent article in the New York Times provided a good example of how the good intentions of humans often lead to intrusions into the natural world. The author explained how she became the self-appointed guardian of birds nesting in her garden. Her small dog was a predator of fledgling birds. She felt obligated to identify all the nests in her garden so that she could keep her dog indoors when the birds left the nest.
When her dog died, she discovered that she could not give up that role. If one bird was competing with another for a nesting spot, she found herself choosing sides, although she knew she had no business choosing winners and losers in the natural world: “It is wrongheaded to interfere in nature when something is neither unnatural nor likely to upset the natural order. I can’t help myself…It’s humiliating, all the ways I’ve interfered.”
We know that volunteers in “restoration” projects mean well. Since they don’t use pesticides or have access to the heavy equipment needed to destroy trees, we don’t argue with them directly. Our advocacy for the preservation of our urban forest is aimed at the managers of our public lands because we are as much the owners of those lands as anyone else and our tax dollars are used to fund their projects.
Matt Chew is one of many professional academics that criticize invasion biology. Unlike most, he emphasizes explaining the weaknesses of eco-nativism using scientific, historical, and philosophical methods, depending on the issue. This has made him a useful collaborator and resource for like-minded but primarily science-oriented colleagues. Million Trees is deeply grateful for his willingness to speak publically about the fallacies of invasion biology, including the generous gift of his time in writing this guest post for us.
Dr. Chew is a faculty member of Arizona State University’s Center for Biology and Society and an instructor in the ASU School of Life Sciences. He teaches courses including the History of Biology, Biology and Society, and a senior conservation biology course in “novel ecosystems,” described HERE on the university’s “ASU Now” news website.
He was also a speaker at the 2013 annual conference of Beyond Pesticides. A video of his presentation is available HERE (go to 24:40). He says that “invasive” plants are convenient scapegoats that are presenting a marketing opportunity for the manufacturers of pesticides. Invasion biology is at the core of the greening of pesticides.
In his guest post, Matt helps us to understand how he chose to pursue a multidisciplinary critique of one topic rather than adopting a single disciplinary approach and identity. He began his professional career as a practicing conservation biologist, experiencing firsthand the sometimes startling disconnects between laws, policies, aspirations, public expectations, and realities “on the ground.”
We celebrate April Fool’s Day with Matt Chew’s article. When we waste our money on ecological “restorations” the joke is on us!
Those familiar with my academic work know I invest most of my efforts documenting and explaining the flaws and foibles of “invasion biology.” But I got into this messy business as a practical conservation biologist, a natural resources planner “coordinating” the Arizona State Natural Areas Program during the late 1990s. I found the toxic nativism of natural areas proponents morbidly fascinating, and the practical politics of natural areas acquisition and management morbidly galling. I chose to follow my fascination. But as “Death of a Million Trees” marks the end of its seventh year as a WordPress blog, and in light of recent decisions by Bay Area authorities, it’s time for a galling reminder: Follow the money.
Authorities responsible for suburban fire suppression and recovery necessarily view stands of living trees as liabilities. They can’t see the forest for the fuels. The prospect of eliminating them merely drives their value further into the negative. That it must be subsidized is ironic because eucalyptus and Monterey pine are plantation grown in many countries for timber or pulp. But they aren’t traditional sources of California wood products and a glut of more familiar drought-killed trees awaits salvage far from finicky neighbors.
So condemned trees can’t just be disappeared by pointing them out to eager loggers. “Concept planning” can be fairly vague, but “action planning” must be very specific. A job this big requires both general and sub-contracting. It requires hiring and training and supervising. Capital equipment will be acquired, maintained and repaired. Affected areas must be surveyed and material volumes estimated. Before trees can be felled, access routes must be surveyed and created. After trees are felled they must be sectioned, staged, loaded and hauled away for disposal. More often they are shredded in place. At every step, someone pays and someone profits.
Where “ecological restoration” is the objective, stumps must be pulled or blasted and roots must be excavated. The eucalyptus seed bank will need to be eliminated or rendered inert. Perhaps even a century’s accumulation of organic topsoil will need amending, or removing and replacing to reconstitute prehistoric substrates. Seed suppliers and nurseries will be contracted to provide plant “native” materials. After the armies of tree-fellers and stump-blasters will come waves of laborers, tractors, diggers, spreaders, and planters in an endless relay of trucks. Ecological restoration is farming, all the more so in proximity to a cityscape arrayed in exotic plants. If all goes well and the rain falls in judicious quantities at auspicious times, planting will be followed by perpetual weeding. At every step, someone pays and someone profits.
It’s hardly surprising that FEMA has no intention of underwriting restoration on that scale. Their plans envision minimally spreading shredded wood, leaving a layer up to two feet deep to gradually decompose, and hoping whatever oaks and other present understory plants they haven’t accidentally fractured or flattened will thrive in the sudden absence of big trees. Two feet of material will gradually compact, but assurances that it will rot into organic soil within a few years are pretty optimistic. Whether and when it will support anything resembling a native plant assemblage is dubious. Meanwhile, some viable stumps will require recurring treatment with the herbicide du jour and occasional supplemental felling. It’s not a reset-and-forget strategy. It’s just the first step of a long and contentious cycle of interventions. And of course, at every step, someone pays and someone profits.
Whenever public property and expenditure is concerned there should be an open procurement process with a clear data trail. A call for proposals is written and published, bids are received, contracts awarded, and work commences. But we can be certain that by the time the prospect of deforesting the Bay Area was openly discussed by policymakers, potential bidders were positioning themselves to influence the shape of the emerging policy and take advantage of it. And various interest groups who saw deforesting the hillsides as a means to their ends became a de facto coalition of advocates. Some acted more openly than others, and some to greater effect. But prominent nonprofit organizations expect returns on their investments. Nothing happens unless someone pays and someone profits.
Some of the premises underlying the logic of the program will inevitably be faulty. Should it falter at any step due to unforeseen events (e.g., meteorological, horticultural, ecological, economic or political), contingencies will be implemented… if funds are available. There are only three certainties. Firstly, no action occurs unless someone pays and someone profits. Secondly, nature, within which I include all aspects of human society, is complex and capricious. No one can predict with much certainty how a post-deforestation landscape will look or function. Finally, a coalition of the discontented will emerge and agitate for improvements that require someone to pay, and allow someone to profit. As Nancy Pelosi recently reminded us, “we’re capitalist and that’s just the way it is.”
We are members of an international team of people who are concerned about the destructive consequences of ecological “restorations.” Trees, Truffles, and Beasts (1) was recommended to us by one of our collaborators in Australia because the book was written by several academic scientists in Australia and the Pacific Northwest of the United States. The book compares and contrasts the forests of these disparate locations and finds that below the ground, they have much in common.
Much more is known about the important ecological functions performed by forests above ground than below ground. However, there are many equally important things happening below ground that are essential to the health of forests:
The soil is inhabited by millions of microbes that decompose organic matter, making it available to plants as nutrients. These microbes recycle dead plants and wood back into usable material for living plants.
Nitrogen is essential to plant growth. Microbes and fungi in the soil convert nitrogen in the atmosphere into forms needed for plant growth. Specific plant species (e.g., legumes, such as acacia and lupine), called nitrogen “fixers,” are mediators in this process.
Fungi in the soil deliver water and nutrients from the soil to the roots of trees in exchange for carbohydrates provided by the trees. This symbiotic relationship is essential for the health of trees and in the absence of fungi, tree growth and development are severely retarded.
Most carbon is stored in the soil, and soil fungi play a role in converting atmospheric carbon dioxide into carbon that is stored in the soil. “Recent research has shown that mycorrhizal fungi hold 50 to 70 percent of the total carbon stored in leaf litter and soil on forested islands in Sweden.” (2)
Relationships between animals and forests
The animals that live in the forests contribute to forest health and forests also benefit the animals.
Fungi in the soil produce “fruiting bodies” that are their means of reproducing. Fruiting bodies above ground are called mushrooms. Fruiting bodies below ground are called truffles. In both cases, they are important sources of food for animals. The animals in Australia are different from those living in the Pacific Northwest, but they have in common that the fruiting bodies of fungi are equally important sources of food for them.
In the case of mushrooms above ground, dispersal of their spores is accomplished primarily by wind. But in the case of truffles, dispersal of their spores is dependent upon the animals that eat them and “deposit” them elsewhere. So, animals are crucial to the reproductive cycle of fungi that fruit below ground.
In their search for truffles, the animals also till the forest floor, which contributes to the decomposition of leaf litter and the dispersal of nutrients into the soil. As the animals defecate in the forest, they are also making contributions to forest health and there are species of microbes and insects that specialize in the use of animal feces.
What happens to the forest ecosystem when it is clear cut?
The forest is a complex and delicate ecosystem. When the forest is destroyed, we should not be surprised to learn that this ecosystem is destroyed. Here are a few of the consequences of clear-cutting a forest:
The forest precipitates fog and the shade provided by the canopy retains that moisture on the forest floor. When we destroy the forest, we lose that source of moisture. The ground dries out in the sunshine. The fruiting bodies of fungi—mushrooms and truffles—require moisture to bloom and they die quickly in the absence of moisture.
The herbicide (Garlon) used to prevent the trees from resprouting is known to damage the mycorrhizal fungi that are essential to forest health. The herbicide that is applied to the tree stump immediately after the tree is destroyed, travels though the cambium layer of the tree down through the roots of the tree. The tree is killed by killing its roots. Mycorrhizal fungi are essentially extensions of the root system. When roots are killed, so are the mycorrhizal fungi. In the absence of mycorrhizal fungi, the survival of “replacement” plants is compromised.
The loss of fruiting bodies as food for animals reduces animal populations and the contributions they make to forest health.
Glyphosate is the herbicide most commonly used to foliar spray non-native vegetation that colonizes the unshaded ground after a clear cut. Glyphosate was originally developed as an anti-bacterial agent. Glyphosate kills bacteria in the soil (and in the mammalian gut, 4) that are playing a role in recycling nutrients to plants (and in digesting our food). (3)
Prescribed burning is another land management method used to eradicate “invasive” plants. In addition to polluting the air, releasing carbon into the atmosphere, and increasing the risk of wildfire, prescribed burns also damage the soil: “Prescribed burning in California pine forest decreased the ectomycorrhizal biomass by almost 90 percent in the upper organic layers of the soil as compared to unburned sites. A decrease of that magnitude in the mycorrhizal energy source of the fungi would affect not only fungal fruiting but also fungal populations.” (1)
In the absence of fungi and bacteria, the soil is essentially sterile and is no longer capable of contributing to the health of a new generation of plants and animals to replace the forest.
Eucalyptus forest in California and Australia
Trees, Truffles, and Beasts was written by academic foresters who are primarily concerned about the destructive consequences of destroying native forests and replacing them with timber plantations, often of another, faster growing species. Ironically, in the case of old growth eucalyptus forests in Australia, the choice of replacement species is often Monterey pines. Since some of the species of mycorrhizal fungi are specific to certain species or types of trees, this change of species is not successful without the inoculation of appropriate species of fungi. For example, some of the mycorrhizal fungi that grow on the roots of conifers are not found on eucalyptus species.
Before writing this article, we corresponded with the authors of Trees, Truffles, and Beasts to confirm that fungi are found in the eucalyptus forests of California. Since eucalyptus was brought to California as seeds, rather than potted plants, we needed confirmation that our eucalyptus forests are also enjoying the benefits of mycorrhizal fungi. We are grateful that the authors replied. They report that eucalyptus forests in California are populated with fungi, including some species that are native to Australia, which implies that some eucalyptus were imported from Australia with native soil. Therefore, we can assure our readers that our description of how the forest functions applies to the eucalyptus forest in California, as well as in Australia.
Predicting the consequences of destroying our urban forest
Plans to destroy non-native forests on 2,000 acres of public land in the East Bay will result in a dry, barren landscape populated primarily by non-native annual grasses. Fantasies that the forest will be magically replaced by a landscape of native plants and trees are just that…fantasies. Every reputable source of information about the planned project predicts this outcome, from the US Forest Service to the Audubon Society and the California Native Plant Society. There are many reasons why this outcome is predictable:
The ground will be covered by as much as 24 inches of wood mulch, which will retard the germination of any plant. The plants most likely to penetrate this physical barrier are those that are most competitive, such as broom and other non-native weeds considered “invasive.”
The moisture available to plants will be reduced by the loss of fog drip and shade provided by the tree canopy. Fog drip in eucalyptus and Monterey pine forests in the East Bay has been measured at 10 inches per year. (5) Young plants and trees require more water than established plants, so the water deficit will retard the growth of a new landscape.
The climate of the San Francisco Bay Area has changed in the 250 years since the arrival of Europeans. Plants that were native at that time are no longer competitive in the warmer, drier climate and an atmosphere higher in nitrates and carbon dioxide. The rapidly changing climate is making the concept of “native” increasingly irrelevant.
And now we know that the damage that will be done to the soil and the forest floor by the destruction of our urban forest will further handicap the successful establishment of a new landscape. Aside from the physical damage done by removing hundreds of thousands of trees with heavy equipment, the herbicides used to kill trees and plants considered undesirable by the perpetrators of this devastating project will sterilize the soil. The resulting weed-dominated moonscape will probably recover in hundreds of years, although the eventual outcome is impossible to predict in our rapidly changing environment. Neither the supporters of this project nor its critics will live to see the recovery.
Chris Maser, Andrew W. Claridge, James M. Trappe, Trees, Truffles, and Beasts, Rutgers University Press, 2008
Peter Del Tredici was invited to speak at a conference sponsored by the Presidio Trust in San Francisco, “Bridging the Nature-Culture Divide Conference by the Cultural Landscape Foundation,” January 23, 2015. Professor Del Tredici recently retired as senior research scientist at Harvard’s Arnold Arboretum after 35 years of service. He is an Associate Professor in Landscape Architecture at the Harvard Graduate School of Design where he teaches courses on soils, plants and urban ecology. He advocates for a pragmatic approach to urban landscapes, which values novel ecosystems for the functions they perform and their sustainability in stressful environments.
Professor Del Tredici’s presentation at the Presidio Conference was entitled, “Saving Nature in a Humanized World.” The presentation is available on YouTube.
We attended his presentation, which was warmly received by an audience of about 180 people. We paraphrase some of his key points.
Update: Professor Del Tredici has requested that the following statement be added to this post: “Professor Del Tredici has graciously allowed us to paraphrase–for educational purposes only–some of his key points in his lecture. In no way should his permission to reprint the lecture on this website be considered an endorsement of the political or ecological agenda of “Death of a Million Trees”
Professor Del Tredici began his presentation by complimenting the Presidio for what it has accomplished in the past 20 years and congratulating the Presidio for “…what it has become. But I’m going to do something very different today. I hope you’re ready for this.”
Professor Del Tredici spoke about spontaneous urban nature, some of which we control but a lot we do not control. What does spontaneous nature look like? The reason why this is important is because it’s about the future. What is the world going to look like 20 years from now? The answer to that question is in urbanized nature.
Detroit is a depressing place from a sociological standpoint. It is so economically depressed that the land has lost its value. Forty percent of the land is no longer occupied or managed by public or private entities. From the standpoint of a botanist, it is a fascinating place because we can see how nature develops without human interaction. Detroit is a case study for urban ecology.
The vegetation of most cities is as cosmopolitan as its human population. Asa Gray’s “Manual of Botany” reports that 10.7% of plant species in Northeastern United States were non-native in 1856. By the 1990s, 25-35% of plant species were non-native. This number is not going down. It’s a strongly upward trend over the past 150 years. We can create little islands of native plants by eradicating non-native species, but the reality is that our ecology is becoming as globalized as our economy. These changes mirrored the changes in the ethnic and racial composition of American cities. The same forces that produce socio-economic changes in cities are also changing the biological environment.
A significant portion of land area in the Northeast is fully urbanized. Urbanization in the West is just as rampant as the Northeast. Looking at an aerial view of Los Angeles, you can see that it is completely developed. You can talk about what used to grow there, but the concept that there is a vegetation that is native to these current conditions, Professor Del Tredici said, “Personally I find that an absurdity. I hate to be so harsh, but nothing is native to LA as it now exists.”
Cities have distinctive environmental characteristics, such as the urban heat island effect. Cities are significantly warmer than rural adjacent areas, which means they are important predictors of the impact of climate change because they have already warmed as much as other places are projected to in the future.
Urbanized areas can also be defined by the amount of impervious surface they contain. When 25% or more of the land is covered with an impervious surface such as roads, parking lots, houses etc., the environment is urbanized from the standpoint of the vegetation because impervious surface fragments the environment, compacts the soil, and interrupts the hydrology. Using the definition of 30% impervious surface, urbanization describes not only our cities, but also many of our suburbs.
Glaciation is analogous to the urbanized environment because the heavy equipment that is used to clear the land leaves in its wake compacted glacial till. What you find after the glaciers recede is barren land; the vegetation has to come back from nothing—a condition known as primary succession.
One-sixth of the city of Boston is built on land fill. What is the native vegetation of filled soil? There is no going back when you’re talking about filled urban landscapes. Not quite as much of San Francisco is built on landfill, but most of the eastern and northern edges of the city are on landfill.
There is a huge difference between native soils and fill soils. Fill soils support the development of novel ecosystems. Native ecosystems cannot be created without native soils. There are some native species that are adapted to urban conditions, such as roadside areas. Urbanized vegetation is a cosmopolitan mix of native and non-native. Urbanization favors species that grow well in soils that are relatively fertile, dry, sunny, and alkaline.
Where it snows, the roads are repeatedly salted to prevent dangerous, icy conditions. This creates alkaline conditions along roadsides to which many plant species are not adapted.
Professor Del Tredici studies modern urban ecology which was born in post-war Germany, where urban environments were reduced to rubble and ecologists began to study what was growing in that rubble. That was the birth of modern urban ecology. It’s important to study, not for what it used to be, but for what it is now and what it can become in the future. Nature reclaiming the urban environment on its own terms is an interesting process, an evolutionary process that we should pay attention to. Post industrial succession—the process of rebuilding ecology in an intensively urban environment– should be studied with the same level of academic intensity as we studied the post-agricultural succession in the Northeast.
When native forests are converted to urban ecosystems and then abandoned—as seen in Detroit– they don’t go back to their original state, rather they become novel ecosystems. There is no going back. Once we achieve the level of compaction and impervious surface of an urbanized environment we have limited what the landscape can become in the future. Some of these changes are permanent. There are long term disturbances caused by chronic stress factors that permanently alter ecological conditions. Professor Del Tredici said, “These conditions are not reversible. Invasive species aren’t going anywhere. If you remove invasive species you are gardening. When you garden you are deciding who lives and who dies. You are just playing god. This gives you the illusion of control, but it is a never-ending effort to control a process that can’t be controlled.”
In 1996 the Arnold Arboretum was given a 24 acre parcel of derelict land, called Bussey Brook Meadow. In 2011, Del Tredici succeeded in preserving it as a site for research on urban ecology by leaving it alone. The land had a 300 year history of use and abuse, all left more or less alone. Plant species—both native and non-native–have sorted themselves out and restored a functional wetland in the middle of the site. It doesn’t matter that it isn’t a native landscape if it is providing the necessary ecological functions.
The Bottom Line
Ecology is not about stasis, it’s about flux. Stasis is achieved by maintenance, but the natural state is flux. Evolution is based on competition, which species is the best adapted to current conditions. Sustainability is about reducing maintenance in order to promote ecology. Landscape architects look at the Bussey Meadow site and ask, “When are you going to fix it?” Professor Del Tredici’s answer is, “I’m not sure this site needs to be fixed. It has value just the way it is.”
These projects have required the destruction of thousands of trees because the native vegetation is grassland and scrub. However, the Presidio has also made a commitment to the preservation of its historic, non-native forest which was planted by the military over 100 years ago. Major investments have been made in reforestation of the aging forest with similar tree species.
In other words, the Presidio Trust seems to have assigned itself a schizophrenic mission to simultaneously destroy an existing landscape in order to re-create it and preserve that same landscape: the re-creation of an idealized landscape vs. preservation of the novel ecosystem within the historic forest. We suppose that is one definition of “balance.” However, we would like to believe that the invitation to Professor Del Tredici to speak of the sustainability of urbanized novel ecosystems is an indication that the Presidio Trust will assign more value to what exists and less effort to attempts to re-create an historic landscape that may no longer be adapted to the real world.
In the not-so-distant past, the goal of ecological “restoration” was usually described as the re-creation of an historical landscape that was believed to have been undamaged by humans, presumed to be “in balance” and therefore sustainable after “restoration” without further human management. In North America, the pre-European landscape is usually selected as the ideal landscape to be replicated, based on the assumption it had not been radically altered by Native Americans. New knowledge has overturned this model:
Invasion biologists have therefore revised their goal for ecological “restorations” to accommodate their new understanding of the dynamic nature of ecosystems.
The revised goal of ecological “restorations”
If the return to an equilibrium state is no longer the goal of ecological “restorations,” what is the new goal? This is how invasion biologists writing in defense of their discipline described their goal: “…we should seek to reestablish – or emulate, insofar as possible – the historical trajectory of ecosystems, before they were deflected by human activity, and to allow the restored system to continue responding to various environmental changes…” (1)
In this post we will deconstruct this new definition of the goal of ecological “restorations.” Our first problem with this new definition is that we don’t know the “historical trajectory” of a landscape because it is fundamentally unknowable. We would have to reconstruct all the events and changes in the environment in the Bay Area in the past 250 years in the imagined absence of any Europeans. Even if we knew what would have happened without our presence, we cannot then ensure the continuation of that imagined environment because, the fact is, WE ARE HERE AND WE AREN’T GOING AWAY!
Because we cannot reconstruct an imagined environment that has not been “deflected by human activity,” restorationists—who are the practitioners of invasion biology–focus on the one element in the environment of which there is sufficient historical knowledge, i.e., plants. Most local restoration projects eradicate all non-native plants and trees, usually using herbicides to accomplish that task. They rarely plant anything after this eradication attempt because they don’t have the resources to do so. Those few projects that re-plant after non-natives are eradicated usually irrigate the new landscape for several years. Here is an incomplete list of everything these projects do not do to replicate an historical landscape:
Soils are not restored for many reasons:
We have no way of knowing the composition of soil 250 years ago.
Soils have been altered by the plants that have been growing in them and by the herbicides used to kill those plants.
Urban soils have high nitrogen levels resulting from exposure to fossil fuel exhaust.
The atmosphere is not restored:
There are much higher levels of ozone and carbon dioxide than there were 250 years ago.
The climate is not restored:
The temperature is higher than it was 250 years ago.
The timing of seasons has therefore changed.
Precipitation and fog have changed in known and unknown ways.
The disturbance events that sustained historical landscapes or set them on another evolutionary course are not restored:
We cannot set fire to urban landscapes annually without polluting our air and endangering our lives.
We cannot allow our creeks and rivers to overflow in urban areas without damaging our properties.
Most occupants of the historical landscape are not reintroduced:
The grazing animals that helped to sustain grassland are gone and cannot be returned to urban landscapes.
The top predators such as bears and wolves that kept grazing and other animals in balance with available resources cannot be returned without threatening our safety in an urban setting.
Many insects that lived in these historical landscapes are unknown to us and some are extinct.
In other words, destroying plants will not “restore” an historical landscape. Nor will it return that landscape to its “historical trajectory” even if that trajectory were known or knowable. Plants live in complex communities in which they are interacting with everything in the environment. Local “restoration” projects do not “restore” an historical landscape because they do not and cannot change anything other than the plants that occupy the space. Because most environmental variables have not been altered by these projects, the landscape will quickly return to its unrestored state unless it is intensively gardened. In that case, the landscape will be continuously “deflected by human activity,” which violates the original goal of invasion biologists.
Misanthropic premise of invasion biology
The revised goal of invasion biology is unattainable because the absence of humans is a prerequisite for its attainment. We cannot know and we cannot replicate a theoretical historical trajectory for ecosystems in which humans were not present. And when we modify ecosystems in an attempt to do so, human activities will determine their future trajectory. The premise of invasion biology is that success of ecological “restorations” depends upon the absence of humans. Therefore, invasion biology has no practical application in the real world.
Carolina Murcia, James Aronson, Gustavo Kattan, David Moreno-Mateos, Kingsley Dixon, Daniel Simberloff, “A critique of the ‘novel ecosystem’ concept,”Trends in Ecology and Evolution, October 2014, Vol. 29, No. 10