Subirdia: Birds adapt to the Anthropocene

 

christmas-holly-4This article is our Christmas present to our readers.  We celebrate the holidays with good news about the birds living in cities all over the world.

Subirdia was written by John Marzluff, an academic ornithologist at University of Washington. (1)  He reports many years of his research and that of his graduate students about the birds that live in urban and suburban Seattle as well as surrounding forest reserves.  He also reports on countless studies of bird populations in similar settings all over the world.  All of those studies reach remarkably similar conclusions.

It took me a long time to read this book because its introduction was off-putting.  Virtually every plant and animal was preceded by the qualifier of “native” or “non-native.”  The implication of the introduction was that the most important feature of every plant and animal is whether or not it is native.  As our readers know, we consider the nativity of plant and animal species largely irrelevant.  All plants and animals are at home in our ideal nature.

Owl nesting in eucalyptus, courtesy urbanwildness.com
Owl nesting in eucalyptus, courtesy urbanwildness.com

When I finally got around to reading Subirdia I was pleasantly surprised.  Although the author has a preference for native plants and animals, in fact, his research and that of others does not justify his obsession.  Where birds are actually found in the greatest numbers is where the habitat is most diverse, not necessarily exclusively native.

Suburbia is very birdy

The conventional wisdom is that cities are inhospitable places for birds and other wildlife.  After all, haven’t we paved over much of their habitat, interrupted their movements by fragmenting their habitat, and drained or covered water resources? In fact, bird populations in urban areas all over the world are both plentiful and diverse.

After years of counting numerous bird species in his hometown of Seattle, the author of Subirdia wondered if Seattle might be unique because it is heavily forested.  After conducting similar surveys in 10 cities around the world, Marzluff is convinced that birds are successfully adapting to rapid urbanization of human society.  The urban centers of cities in North and Central America, New Zealand and Europe support an average of 23 bird species.  He found the least number of bird species (11) in Auckland, New Zealand and the greatest number (31) in St. Andrews, Scotland.

Starling in breeding plumage. Creative Commons - Share Alike
Starling in breeding plumage. Creative Commons – Share Alike

Another popular myth about the loss of bird diversity in the Anthropocene is that the globalization of human civilization produces “homogenized” nature.  That is, many people believe that bird populations may not be in decline, but there are a few hardy species that dominate everywhere.  Again, Marzluff’s studies do not corroborate that belief.  Five bird species are found in cities all over the world (house sparrows, starlings, Canadian geese, mallard ducks, and rock pigeons).  However, these ubiquitous species are not the predominant bird species he found in cities.  Of the 151 different bird species he found in the 10 cities he visited, 75% of them were unique to each of the cities.   “Homogenization is barely perceptible.” (1)

Comparing bird populations in cities with nature reserves

Marzluff also compared bird populations in cities with undeveloped nature preserves.  Once again, cities still look like good homes for birds.  He finds twice as many bird species in Ketchikan, Alaska as in the nearby wildlands along the Naha River, “a remote wilderness fifty miles away…that required powerboat, kayak, and hiking to attain.” (1)

He also visited Yellowstone National Park, a 2.2 million acre protected area within an undeveloped ecosystem of nearly 20 million acres, where he counted 26 bird species in four days.  From there, he flew to New York City where he counted 31 bird species in Central Park in only three days.  Historical records of bird surveys in Central Park and Yellowstone National Park indicate that about 200 bird species have been found in both parks since the late 19th century.  “From a bird’s perspective, a large park created by human hands or by nature is not all that different.”  (1)

Accommodating birds in cities

Marzluff’s concluding chapters advise city dwellers how to encourage and support birds.  His “ten commandments” for accommodating birds make no mention of planting native plants or eradicating non-native plants:

  • “Do not covet your neighbor’s lawn.”
  • “Keep your cat indoors.”*
  • “Make your windows more visible to birds that fly near them.”
  • “Do not light the night sky.”
  • “Provide food and nest boxes.”
  • “Do not kill native predators.”
  • “Foster a diversity of habitats and natural variability within landscapes.”
  • “Create safe passage across roads and highways.”
  • “Ensure that there are functional connections between land and water.”
  • Enjoy and bond with nature where you live, work, and play!”

Marzluff expresses a strong preference for native plants throughout his book, but his research in Seattle is inconsistent with that preference:  “The forests of Seattle and its suburbs now embrace 141 species of trees, including 30 native species and ornamentals from North and South America, Europe, Asia, and Africa.  Some are problematic invaders, but in total they provide a diverse menu of foods and nesting and roosting sites for birds.”  (1)

Why a preference for natives?

Garter snake in eucalyptus leaf litter. Courtesy Urban Wildness
Garter snake in eucalyptus leaf litter. Courtesy Urban Wildness

Another academic scientist in Washington State, Linda Chalker-Scott, directly addresses the vexing question of why public policies which mandate the use of native plants have proliferated despite the lack of evidence that they are superior in any way.  She focuses on this question:  “Do native and nonnative woody species differ in how they affect species diversity?”  Her literature search found 120 studies from 30 countries that quantified the biodiversity of birds, insects, mammals, reptiles, and other plants in woody plants and trees in urban landscapes.

The analysis of these studies reveals that “the science does not support the supposition that native plantings are required for biodiversity…it is clear that an automatic preference for native trees when planning in urban areas is not a science-based policy.” (2) The assumption that native plants are superior to non-native plants is based on these misconceptions:

  • The definitions of native and alien species are value judgments, not science-based concepts.
  • Native plants are often poorly suited to environmental conditions in urban areas, such as compacted soil and changes in the climate. Conversely, introduced plants are often well suited to these urban conditions.
  • Many introduced plants provide valuable ecological benefits. For example, they often provide food, pollen, and nectar resources during winter months when native plants are dormant.
  • Tropical milkweed is not native to California. (Asclepias curassavica) Creative Commons
    Tropical milkweed is not native to California. (Asclepias curassavica) Creative Commons

    Doug Tallamy is the academic scientist most closely associated with the native plant ideology. His claim that insects require native plants is based on his mistaken assignment of nativity to an entire genus, when only a few species within that genus are actually native.  For example, there are over 35 species of milkweed in the genus Asclepias, but only two species are native to California.  Most members of the milkweed family are useful to monarch butterflies.  It is therefore not accurate to claim that monarchs require native plants.  They have lived all over the world for over 200 years in some places where there are no native species of milkweed.

Chalker-Scott’s meta-analysis of 120 studies concurs with Mr. Marzluff:  “The published research overwhelmingly identifies diversity, structure, and function as the most important vegetation characteristics for enhancing community biodiversity…In fact, sometimes landscapes require the inclusion of exotic trees and control of natives to maintain diversity.” (2)

Doing more harm than good

Our readers know that we do not begrudge the preference of native plant advocates for native plants.  We encourage them to plant whatever they want.  We only ask that they stop destroying the plants they don’t like.  That request is based on our belief that they are doing far more harm to our public lands than any perceived benefit of native plants.  Much of that harm is caused by the widespread use of herbicides to destroy non-native vegetation.  These herbicides are known to damage the soil and they migrate in the soil, damaging neighboring plants that are not targeted.  These issues are surely a factor in the conspicuous lack of success of their “restorations.”  There is also mounting evidence of the toxicity of herbicides to bees, birds, and other animals including humans.

But there is another, equally important reason why we object to the futile attempts to eradicate non-native plants.  They are providing valuable habitat for wildlife.  Even when they are replaced by native plants after being destroyed, the animals that depended upon them are not necessarily restored to the landscape.  In fact, few projects plant natives after the eradication of non-natives.

Japanese honeysuckle. Attribution William Rafti
Japanese honeysuckle. Attribution William Rafti

A recently published study (3) of the removal of Amur honeysuckle (Lonicera maackii) is an example of the loss of valuable habitat.  The hypothesis of this study was that “invasion of urban habitats by exotic plants was the underlying mechanism driving changes in bird-plant networks.”  The study tested this hypothesis by comparing forest plots dominated by honeysuckle with those in which honeysuckle had been removed and the surrounding forest habitat replicated.  They measured nesting birds, nest predators, and nest survival.

They found that the lowest overall nest survival rates were found in the plots in which honeysuckle had been removed.  In other words, “…removal of invasive honeysuckle from urban forests did not restore network structure to that of rural landscapes.”  The authors concede, “This finding was not consistent with our original hypothesis that invasion of forests by the exotic Amur honeysuckle was responsible for the urban-associated changes in bird-plant networks.”  They conclude, “The degree to which native communities can be restored following removal of exotic plants remains unclear.” 

Actually, we think it is quite clear that eradicating non-native plants does not benefit man or beast. We marvel that the fantasy persists that there is some theoretical benefit to killing harmless plants, despite the consistent lack of evidence of any benefit and the considerable evidence of the harm of such attempts. 


*Like most ornithologists, Marzluff comes down hard on cats as killers of birds in his book.  However, he cites just one study about predation of fledglings.  The study used radio transmitters to determine the fate of 122 newly fledged birds over a period of two years.

The results do not justify the demonization of cats:  “Only 20 percent of radio-tagged birds died during our study.  Birds such as Cooper’s hawks and mammals such as Townsends’ chipmunks, ermine, and Douglas squirrels were the most likely predators.  The most notorious of all bird predators, the out-of-the-house cat, was implicated in only one death, though we could never be entirely sure which mammal or which bird had killed the fledging.”  (1) Marzluff credits a neighborhood coyote for controlling the cat population.  Frankly, that doesn’t make sense.  Chipmunks and squirrels are just as likely to be prey for the coyotes.

We have reported on similar studies which reach the same conclusions.  A meta-analysis of 8 studies of nest predators of song birds in North America used video cameras to identify the predators of 242 depredation events.  Only one of those nest predators was a cat.

We have no objection to the general advice to keep your cat indoors. (We have never had a cat and don’t plan to.)  However, we think that estimates of birds killed by cats are greatly exaggerated.  Humans seem to have an unfortunate desire to look for scapegoats and cats seem to fit the bill for bird lovers.

  1. John M. Marzluff, Welcome to Subirdia,” Yale University Press, 2014
  2. Linda Chalker-Scott, “Nonnative, Noninvasive Woody Species Can Enhance Urban Landscape Biodiversity,” Arboriculture & Urban Forestry, 2015, 41(4): 173-186
  3. Amanda D. Rodewald, et. al., “Does removal of invasives restore ecological networks? An experimental approach,” Biological Invasions, March 2015

Global increases in biodiversity resulting from new species

Great horned owl in eucalyptus.  Courtesy urbanwildness.org
Great horned owl in eucalyptus. Courtesy urbanwildness.org

One of the most popular justifications for eradicating non-native plants is the claim that they will out-compete native plants, ultimately causing their extinction.  Innumerable studies have found no evidence to support that claim, but the belief persists amongst those who demand the eradication of non-native plants.

Islands have been considered particularly vulnerable to extinctions because they contain many endemic species (found only on that island) that have evolved in physical isolation from their ancestors from other places and become unique species.  And there were many animal extinctions–particularly of flightless birds–with the arrival of humans who were both their predators and brought predators with them.

However, despite the conventional wisdom that the introduction of new species of plants to islands would result in extinction of their predecessors, there is no evidence that this is indeed the case with introduced plants.  In 2008, Dov Sax and Steven Gaines published a study of species diversity on islands.  This is what they found:

Honeybee on wild mustard.  Courtesy urbanwildness.org
Honeybee on wild mustard. Courtesy urbanwildness.org

Predation by exotic species has caused the extinction of many native animal species on islands, whereas competition from exotic plants has caused few native plant extinctions…By analyzing historical records, we show that the number of naturalized plant species has increased linearly over time on many individual islands. Further, the mean ratio of naturalized to native plant species across islands has changed steadily for nearly two centuries. These patterns suggest that many more species will become naturalized on islands in the future.” (1)

In other words, the introduction of new plants to islands has not resulted in extinctions of the plants that preceded them.  Therefore, the result of plant introductions has been greater plant diversity on islands.

But what about the continents?

Painted lady butterfly on Weigela.  Courtesy urbanwildness.org
Painted lady butterfly on Weigela. Courtesy urbanwildness.org

Recently a new study was published that asked the same question on a global scale:  Has the introduction of new plants and animals resulted in the extinction of their predecessors?  The answer is a resounding NO!  (2)

The study was conducted on a huge scale by an international team of scientists:

  • “6.1 million species occurrence records from 100 individual time scales”
  • “35,613 species were represented…including mammals, birds, fish, invertebrates, and plants”
  • “The geographical distribution of study location is global, and includes marine, freshwater, and terrestrial biomes, extending from the polar regions to the tropics in both hemispheres.”
  • “The collective time interval represented by these data is from 1874 to the present, although most data series are concentrated in the past 40 years.”

Like most scientists who expect to find evidence of decline, this team of researchers was surprised to find little evidence of loss.  Here are some of their key findings:

  • “Surprisingly, we did not detect a consistent negative trend in species richness or in any of the other metrics of α diversity.”
  • “There is no evidence of consistent loss of biodiversity among terrestrial plants.”
  • “Time series for terrestrial plants exhibit, on average, a positive slope for species richness.”
  • “Collectively, these analyses reveal local variation in temporal α diversity but no evidence for a consistent or even an average negative trend.”  (Alpha diversity is species richness at the local level.)
  • “An analysis of slopes by climate regions reveals that temperate time series have a significantly positive trend…”

In other words, new plants result in more plants, particularly where we live, in the temperate zone.  There is no empirical evidence that new plants have resulted in the loss of the plants that were there before they arrived.

So what’s the beef?

Song sparrow in wild radish.  Courtesy urbanwildness.org
Song sparrow in wild radish. Courtesy urbanwildness.org

You might think that this huge new study would put the controversy to rest.  You would be wrong.  For every answer we find, there is a new question from nativists.  The response of native plant advocates to the good news that the plants they prefer will not disappear if new plants are allowed to live in their company is that the plant world is being “homogenized.”  They say that if new plants are permitted to remain, all landscapes will become the same, resulting in the loss of unique landscapes that existed in the past.

They are, of course, mistaken.  Their dire prediction will not come to pass because the biotic and abiotic conditions of every landscape are unique.  The climates are different.  The soils are different.  The atmosphere is different.  The plants and animals that are there when they arrive are different.  If the new plant survives in its new home, it will be capable of adapting to these local conditions and over time it will change, ultimately becoming a unique species.  When the first family of monkeys made the voyage from Africa to South America, they were the same species as those they left behind.  Now they are unique species as a result of genetic drift and genetic divergence.

The process of adaptation and evolution is often more rapid than we expect.  Sometimes such changes have occurred within the lifetimes of scientists who were able to witness these changes.  More often, the changes occur more slowly and are only visible in museum collections or fossil records.

Consider the consequences

Garter snake in eucalyptus leaf litter.  Courtesy urbanwildness.org
Garter snake in euclypatus leaf litter

It is physically impossible to prevent the arrival of new species.  Even when they are not intentionally introduced they find a way to piggy back on the daily activities of humans.  They arrive on our airplanes and cargo ships.  We aren’t going to stop importing or exporting our products all over the world.  Nor are we going to quit traveling.  We must accept the consequences of the way we live and quit blaming plants and animals for their passive participation in our movements.

Aside from the question of whether or not it is physically possible to stop the arrival of new plants and animals, let’s acknowledge that at least in the case of plants no great harm has come from their introductionSince we now enjoy more plants than were here when they arrived, just what is it that we’re griping about?  We seem to be griping about change.  Change will occur whether we like it or not.  We can’t prevent change, so we must quit fighting against something that we are powerless to prevent.  That is the definition of wisdom.

Finally, we must consider the consequences of trying to eradicate non-native plants that are firmly entrenched in our landscapes.  Huge amounts of herbicide are being used in the futile attempt to eradicate them.  Fires that pollute the air and endanger our homes are set for the same purpose.  Trees that are performing valuable ecological functions are being destroyed.  The animals that use these plants and trees for food and cover are being deprived of their homes and their food.  We are doing more harm than good.


 

  1. Dov Sax and Steven Gaines, “Species invasions and extinctions: The future of native biodiversity on islands,” Proceedings of the National Academy of Sciences, August 12, 2008
  2. Maria Dornelas, et. al., “Assemblage times series reveal biodiversity change but not systematic loss,” Science, April 18, 2014

Climate Change vs. Biodiversity: NOT!!

A new study reported changing public and scientific interest in biodiversity compared to climate change.  Using reports in the media and scientific journals in the United Kingdom and the US, as well as funding of scientific studies by the World Bank and the National Science Foundation, the study reports that the interest in climate change has increased and the interest in biodiversity has decreased in the past 25 years.

This analytical approach seems to suggest that these two environmental issues are mutually exclusive, that the interest in one is at the expense of the other.  We find this both unfortunate and unnecessary because we consider these two issues intimately related.  Climate change is increasingly the biggest threat to biodiversityIf plants and animals are unable to adapt to climate change, they are doomed to extinction. 

Therefore, we believe that science should study these topics together.  In fact, the study on which we are reporting acknowledges the relationship between these topics:  “Dual-focus projects are being funded more often, but… ‘this is relatively small and does not mitigate the plateauing expenditure on biodiversity research.’” (1)

Conservation in a changed climate

As long as conservation and “restoration” projects are devoted to replicating historic landscapes, they are likely to be unsuccessful.  The climate, atmosphere, and soil conditions are no longer suited to a landscape that existed hundreds of years ago, particularly in urban environments.  Therefore, if biodiversity is to be preserved by conservation and restoration, such projects must look forward, not backwards. 

We have been watching the Nature Conservancy closely for signs that it is adapting to climate change.  We look to the Nature Conservancy to lead the way because they employ hundreds of scientists.  In contrast, many mainstream environmental organizations employ more lawyers than scientists.

We have reported that the Conservancy’s Chief Scientist, Peter Kareiva, is at least paying lip service to an approach to conservation that takes into consideration the profound changes in the environment caused by the activities of man.  This acknowledgement of the irreparably altered environment is encapsulated by the proposal to name a new geologic era, the Anthropocene.

Unfortunately, the old guard of conservation biology has engaged in a vigorous campaign to silence the Conservancy’s new approach.  This conflict between the old guard and scientists who have proposed a more realistic approach to conservation was recently reported by the New Yorker. (2)  According to that article, Peter Kareiva has made a commitment to the old guard to quit publishing anything regarding the Anthropocene and its implications for conservation practices.

The Nature Conservancy has responded to the article in the New Yorker in its on-line blog.  It doesn’t explicitly address the question of whether or not a commitment has been made to quit advocating for a more realistic approach to conservation.  However, it implies that the Conservancy plans to continue on a course of scientific innovation and experimentation, which it describes as “practical.”  Here is a specific choice made by the Conservancy that typifies this approach:

Monarch butterflies roosting in eucalyptus tree.
Monarch butterflies roosting in eucalyptus tree.

“We know it was worth spending millions of dollars to rid Santa Cruz Island of non-native pigs.  But we are pretty sure it would not be worth spending what could be hundreds of millions of dollars to rid California of non-native Eucalyptus trees (which also happen to harbor wildlife and monarch butterflies.)” (3)

Although the Nature Conservancy’s Chief Scientist may have agreed to “shut up,” we see signs of the Conservancy’s new approach in its latest magazine.  In a brief article entitled “Forests of the Future,” the magazine reports that they are no longer planting the species of trees that existed in the past in one of their properties in Minnesota, because they don’t believe that species is adapted to current or predicted future conditions.  Instead they are actively engaged in reforestation of the land with new species:

Over the past two springs, the team planted 88,000 tree seedlings across 2,000 acres in the northeastern corner of the state.  The seedlings consisted of species that should survive better in a warmer and drier climate—trees, such as red oak, found in higher numbers just south of the area. For a team accustomed to restoring forests to match historical landscapes, helping the North Woods [of Minnesota] adapt to a predicted future climate is a new but necessary idea.  [The Conservancy’s science director in Minnesota] says, ‘All of our modeling is saying the same thing,’ she adds, ‘We needed someone to actually go out and start trying some of this stuff.’” (4)

Looking forward not back

We are very encouraged by the Conservancy’s new approach and we hope that other land managers will be inspired by it.  We are also reminded of a recent visit to a nature reserve near San Luis Obispo managed by the local chapter of the Audubon Society.  We reported about this reserve in a recent article because the land managers had planned to destroy all eucalyptus trees on that property but were forced to scale back their plans in response to a noisy negative reaction from the public.

Dying oak tree, Sweet Springs Nature Reserve
Dying oak tree, Sweet Springs Nature Reserve

On our recent visit, we learned that this was a wise choice because many of the oak trees that were planted on this reserve by those who wish to “restore” it are quite dead despite the fact that the reserve has an extensive irrigation system.  These land managers looked back and the result of that retrospective thinking is a landscape of dead native trees.

Irrigated native plant garden, Sweet Springs Nature Reserve
Irrigated native plant garden, Sweet Springs Nature Reserve

Climate change requires land managers to wake up to the realities of what will grow where.  Land managers in the San Francisco Bay Area appear to be blind to that reality.  They repeatedly plant species where they grew hundreds of years ago and we are forced to watch the plants die repeatedly. 


 

 

(1)    “Climate change beats biodiversity as a press, scientific, and funding priority,” Science Daily, June 11, 2014

(2)    D.T. Max, “Green is Good,” New Yorker, May 12, 2014

(3) Mark Tercek and Peter Kareiva, “Green is Good:  Science-Based Conservation in the 21st Century,” May 5, 2014

(4)    “Forests of the Future,” Nature Conservancy, June/July 2014

What is “biodiversity?”

We are republishing an article from the San Francisco Forest Alliance with their permission and the permission of the author of the article, Professor Arthur Shapiro, UC Davis. 


 There’s been a lot of talk of ‘biodiversity’ in San Francisco recently. The city’s ‘Recreation and Open Space Element’ (ROSE) mentions it without clearly defining it. The Natural Areas Program claims to preserve it. There’s a new position, the Biodiversity Coordinator (currently Peter Brastow, formerly of Nature in the City) within San Francisco’s Department of the Environment.

One of our readers, puzzled by all the discussion, asked a simple question of UC Davis Professor Arthur Shapiro, who gave a talk at the Commonwealth Club a few days ago. Instead of the two-line answer they expected, he sent this detailed response — which he kindly permitted us to publish.

WHAT IS BIODIVERSITY? BY ARTHUR M.SHAPIRO
A buzzword. Biodiversity means whatever you want it to mean. I hate the word. Here’s why.

The following is from the introductory biology textbook we use at U.C. Davis, Life: The Science of Biology, (10th edition, Sadava et al., p.1229 — yes, I said p. 1229!):

“…the term BIODIVERSITY, a contraction of ‘biological diversity,’ has multiple definitions. We may speak of biodiversity as the degree of genetic variation within a species….Biodiversity can also be defined in terms of species richness in a particular community. At a larger scale, biodiversity also embraces ecosystem diversity–particularly the complex interactions within and between ecosystems….One conspicuous manifestation of biodiversity loss is species extinction…”

Got that?

The glossary at the back of the book defines “biodiversity hot spot” (itself ambiguous, conflating numbers of species and degree of endemism), but NOT biodiversity itself. One can see why.

Where did this verbal monstrosity come from?

Heliconius mimicry.  Creative Commons Generic 2.0
Heliconius mimicry. Creative Commons Generic 2.0

The raw number of species in a defined area or system – what many of us call “species richness“–is a useful number. There are more species of butterflies in Brazil than in California, and more in California than in Alaska. That is true even if we pro-rate species number by area, and it is not trivial to ask why.

But there is more to biodiversity than mere numbers of species.  Ecologists are also interested in how individuals are divided among species, that is, the distribution of commonness and rarity among species. You can have a  “community” consisting of exactly two species.  It could have, say, 50 individuals of each species, or it could have 99 of one and 1 of the other–or any ratio in between. Does this matter? Why? What can those numbers tell us?

QUANTIFYING DIVERSITY – A DIVERSITY INDEX

A century ago a Danish plant ecologist named Christen Raunkiaer observed that there was a statistical regularity to this; he called it the “law of frequency.” In subsequent years it was found to hold for bird censuses and moths collected at lights, as well as for old-field plants. A whole series of mathematical models developed over the years attempted to account for this regularity by means of assumptions about how species interacted–competing for resources, for example.  These exercises were at the core of community ecology for several decades, and were seen as immensely important.

During World War II an applied mathematician named Claude Shannon, working on war-related communications problems at Bell Labs, developed a formula that concisely expressed the information content of a message. Ecologists discovered the Shannon formula in the 1960s and realized it could easily be adapted to give a single number that combined the number of species in a community and their relative abundances.

Thus whole communities could be compared efficiently, a potentially informative and useful tactic in trying to understand how multispecies systems worked. The number generated by the Shannon formula came to be called diversity, and the formula became the first and most widely-used of several diversity indices. I learned it in high school and I still use it in teaching. Diversity had two components, then:

  • Species richness and
  • “Equitability,” (the difference between a 50:50 and a 99:1 community).

And we were off and running. Now everything could be quantified with a diversity index: “foliage height diversity” in a forest canopy, or “aspect diversity” in moth faunas (how many wing shape-pattern themes could be recognized?). The number of uses and abuses of the term multiplied like rabbits. By 1971 things had gotten so bad that a paper was published caustically titled “The nonconcept of species diversity.” It was widely applauded for its candor.  Unfortunately, the author ended up inventing his own new measure of diversity–one he thought was better than the old ones.

MORE LEVELS OF ‘BIODIVERSITY’

But things could get worse. And they did. With the passage of the Endangered Species Act, which opened the door to protection of endangered subspecies (keep in mind that there is no concept of the subspecies; a subspecies is whatever some taxonomist says it is) and even “distinct population segments” (no one knows what that means), genetics got in on the diversity game. Now we would not be content with diversity at the species level; we needed to
get inside species.

In the scramble to define what might be protectable, a search was launched for “evolutionarily significant units.” With modern molecular-genetic tools, we quickly learned that taxonomic subspecies may be genomically nearly identical, while organisms indistinguishable by the naked eye may be wildly different. Defining diversity at the genetic level is still, well, challenging.

One very useful dimension of biodiversity is known as alpha, beta and gamma diversity:

  • Alpha diversity is species richness at the local level.
  • Beta diversity is a measure of how much the biota of different localities within a region differ among themselves–that is, how quickly species composition “turns over” in space [i.e. when you have many different little ecosystems next to each other].
  • Gamma diversity is at a large spatial scale.

The Bay Area has phenomenally high beta diversity in almost everything.

THE BOTTOM LINE

So what is biodiversity? It’s species richness, plus the distribution of abundance and rarity, plus the geography of all that, plus the amount of genetic variation in selected species of interest, plus whatever you please.

Somehow or other concepts of “quality” have gotten mixed in, too. When you clear-cut a redwood forest (which has very low species richness), the early-successional communities that develop on the site, which may be dominated by “invasive weeds,” will have both much higher species numbers and a richer distribution of species abundances than the forest they replaced. But early-successional communities don’t get any respect despite being more diverse and despite the supposition that biodiversity is good. Because they’re made up of the ‘wrong’ species–whatever that means.

Because biodiversity, after all, is only a buzzword.


 

Dunnigan Test Plot, Augusst 2011.  The result of an eight-year effort to restore native grassland.  Does it look "biodiverse?"  ecoseed.com.
Dunnigan Test Plot, August 2011. The result of an eight-year effort to restore native grassland. Does it look “biodiverse?” ecoseed.com.

Addendum:  We have recently learned that Peter Brastow, San Francisco’s Biodiversity Program Coordinator, has applied for an Urban Greening Planning Grant for the City of San Francisco to fund the creation of a Biodiversity and Ecology Master Plan.  This grant application was submitted to the State of California’s Strategic Growth Council for $250,000.

This Master Plan would “identify land owners at the parcel level” (including your backyard;  see below*) for “consolidating ownership and/or management of wild lands and natural areas into as few departments as possible in order to facilitate coherent and higher quality habitat restoration and management.”  The Natural Areas Program “serves as a model for extending this work beyond Recreation and Park Department lands.”  (Quotes are directly from the grant application.)  In other words, the Biodiversity and Ecology Master Plan will extend the work of the Natural Areas Program to all open space in San Francisco, regardless of the current ownership of the land.

The complete document is available here:  Biodiversity Action Plan – grant application questions.final.  We find this a horrifying prospect.  The Natural Areas Program is extremely controversial because it destroys existing habitat, uses large quantities of toxic herbicides, and restricts access to designated trails.  Applying these policies into all open space in the city is a bad idea

– Million Trees

*The grant application says, “We will review the potential of rear yard open space, green roofs, green walls, landscaping, street trees, mini and pocket parks, and other urban design potential to enhance biodiversity in the urban landscape.”

Scientists critique UCSF’s plans for Mount Sutro and native plant advocates react

Nature is considered one of the top journals in science globally.  So, we were very excited about the article they published in their September 2013 edition about Mount Sutro. (1) The article starts with every bogus claim UCSF makes to justify the destruction of the forest, i.e., that it is flammable, that it is diseased, that it will store more carbon when most of it is destroyed.  We have responded to those claims many times on Million Trees, so we won’t repeat those arguments here.  (We have provided links to our articles about each of these issues, so you can read them if you wish by clicking on each issue.)

Sutro forest before recent tree removals.  Courtesy Save Sutro
Sutro forest before recent tree removals. Courtesy Save Sutro

After faithfully repeating UCSF’s storyline, Nature turns to the opposite side of this debate, starting with the welcome introduction of critics of the Sutro project as “environmentalists and ecologists” for whom “a hardline devotion to preserving native ecosystems is giving way to a more post-modern idea of what constitutes a natural landscape.”  The author of the Nature article interviewed scientists who agree with this new perspective:

  • “’Mount Sutro is part of a larger story,’ says Richard Hobbs, an ecolo­gist at the University of Western Australia in Crawley. ‘What some people see as a weed-filled blot on the landscape, others see as something extremely valuable, worthy of managing in its own right. People are increasingly moving away from the belief that a native ecosystem is always best….There is a lot of tension about how to deal with situations like these right now,’ he says. ‘With so much non-native habitat, the old views — that everything must be natural — no longer apply.’”
  • “In the early 1990s, Patricia Kennedy of Oregon State University in Corvallis helped to develop management guidelines for northern goshawks. She found that the raptors do not strictly need old-growth forests; land used for timber harvesting can work, too. She says that, at the time, accept­ing the idea felt like a move to the ‘dark side’. ‘The whole culture in wildlife biology and conservation circles has been that you can’t approximate Mother Nature,’ she says.  But those ideas are changing today, with altered ecosystems such as Mount Sutro’s providing a case in point.”
  • Joe Mascaro, an ecologist at Stanford University in California [2] who has been publicly critical of UCSF’s management plans, says that Mount Sutro has long since given way to a completely new ecosystem. ‘Restoring it to an original state would be borderline impossible, so why stop the succession that is already in place?’”
  • “Resistance to such a heretical idea runs deep among ecologists, but growing num­bers are embracing altered ecosystems in the name of pragmatism. ‘You can reach more win–win situations if you don’t insist on purity,’ says Katharine Suding, an ecologist at the University of Califor­nia, Berkeley, who specializes in restoring human-affected areas. ‘It doesn’t have to be a natural versus non-natural dichotomy.’”
Same section of Sutro forest after tree and understory removal at the end of August 2013.  Courtesy Save Sutro
Same section of Sutro forest after tree and understory removal at the end of August 2013. Courtesy Save Sutro

The reaction of native plant advocates

As pleased as we were to hear from the international scientific community, we didn’t fully appreciate the significance of the article until we read the reaction of native plant advocates in Jake Sigg’s Nature News:

“On Sep 15, 2013, at 4:13 PM, Peter Brastow wrote (re NYT editorial on Mt Sutro):
‘Yes, and recall that the NYT article linked to an awful piece in Nature. I see this as PhD Academicians liking the sound of their own voice, and certain members of the media who, likewise, don’t actually know anything about on-the-ground land management. To boot, their arguments support continued environmental destruction around the world, whether for palm plantations, bio-fuel production, cattle grazing, suburban development, you name it. Do you think these same people advocate letting the Amazon rainforest be clearcut from end to end?’” 
(Jake Sigg’s Nature News, September 21, 2013)

It seems that native plant advocates disliked the Nature article as much as we liked it. This comment from a prominent native plant advocate in San Francisco is more evidence of the growing gap between restorationists and the scientists of invasion biology who spawned the native plant movement.  We have noted before the inevitable tension between theoretical science and its practical application and in the case of ecological restoration in the Bay Area, it is becoming more and more distant from its scientific underpinnings.

What is San Francisco’s Biodiversity Program?

You might think that the loss of scientific support for the projects in the Bay Area which are attempting to convert non-native to native landscapes would weaken the local native plant movement.  You would be mistaken.  Peter Brastow, the author of this comment, is employed by the City of San Francisco as the Director of Biodiversity in the Department of the Environment.  The creation of this program and the selection of Mr. Brastow as its first director suggest official endorsement of these projects and imply their expansion beyond their present footprint.  This is the mission of San Francisco’s Biodiversity Program according to the Department of Environment’s website:

“The mission of the Biodiversity Program is to conserve the biodiversity, habitats and ecological integrity of San Francisco’s natural environment, toward a comprehensive watershed- and ecosystem-based natural resources management, stewardship and education program.

Our approach is to advance collaboration and coordination for biodiversity policy development and interagency conservation planning and management.

San Francisco’s indigenous biodiversity exists among diverse open lands and habitats in a complex urban geography of parklands, natural areas, urban forests, community gardens and backyards. The scope of the program includes protection of all of the City’s biological diversity and natural lands, and for strategic integration of nature conservation best practices into planning, implementation and education for the built environment.

We hope to raise the bar on integrating considerations for nature and biodiversity into the operations of every City Department as well as into every aspect of city life, including making significant increases in public and City employee awareness.”

Our interpretation of this vague, abstract description is that the goal of San Francisco’s Biodiversity Program is to extend the native plant restorations of the Recreation and Park Department’s Natural Areas Program to all city departments and all city-owned open space, perhaps even to your backyard.

Since we think the Natural Areas Program has been a miserable failure, with respect to successfully converting naturalized non-native landscapes to native plant gardens, we have serious doubts about expanding the program to the entire city.  And since the Natural Areas Program is using a great deal of pesticide, destroying many healthy trees, and plans to destroy thousands more, we are not enthusiastic about subjecting more public land to such damage.

We are equally alarmed by the dismissal of scientists by the Director of Biodiversity, Peter Brastow, as people who like to hear themselves talk.  This suggests that the Director of Biodiversity isn’t listening to the rapidly changing science of invasion biology.  You might wonder what Peter Brastow’s qualifications are to enable him to dismiss academic scientists as a resource for the application of invasion biology to native plant restorations.  You can visit his resume on the internet to satisfy that curiosity.

Pot-calls-kettle-black

For the record, we are not supporters of the “environmental destruction” of which Mr. Brastow accuses the scientists who are quoted in the Nature article.  We do not “advocate letting the Amazon rainforest be clearcut from end to end,” as Mr. Brastow claims.  We are confident that no one else with whom we collaborate does so either.  The only clearcutting we have witnessed first-hand was done in response to the demands of native plant advocates; these projects have already destroyed 18,000 non-native trees in the East Bay hills and are determined to clearcut about 80,000 more.  This looks like a classic case of “pot-calls-kettle-black.”

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(1)    Danielle Venton, “Forest management plans in a tangle,” Nature, September 2013, Vol. 501

(2)    When Mr. Mascaro was interviewed, he was at the Carnegie Institute of Research in Stanford, California.

“How economic growth will help prevent extinction”

Earth.  NASAThe latest issue of The Economist magazine contains a special report about biodiversity which is previewed on its cover as “How economic growth will help prevent extinctions.” (1)  That’s a counterintuitive statement, but one we might expect from The Economist because it is an unashamed promoter of capitalism.  Although it has a viewpoint, its readers also rely on it for accurate reporting about international issues and events.  So, we read the special report about biodiversity with great interest.

How does economic development support biodiversity?

At the early stages of development, biodiversity suffers from the inevitable pollution associated with industrialization.  As development progresses and a society becomes more affluent, biodiversity benefits from the regulation that people begin to demand from their governments. 

In the United States, for example, tremendous progress has been made in cleaning up our water and air since the 1970s, an era of environmental regulation.  Two-thirds of our rivers were considered unsafe for swimming or fishing 40 years ago.  Only one-third are still considered unsafe. (That still seems like a lot.)   Likewise, the development of the Chinese economy has produced horrendous levels of pollution and their prosperity is just recently creating the demand to address the problem.   When we clean up our air and water, the animals with which we share the planet benefit as much as we do.

In the initial stages of development, population often increases as death rates from treatable diseases decline, which is Africa’s current stage of development.  However, education becomes more widely available as a society becomes more affluent and birth rates decline when more women are educated.  

Agricultural methods are improved by greater economic resources and education.  Improved agricultural techniques make land more productive so that less land is used for agricultural purposes.  More land becomes available for preservation and recreation.  Less labor required by agriculture increases urbanization which also uses less land.  In 1985, a study reported that “protected areas” were only 3.5% of the planet’s land area.  By 2009, another study reported that “protected areas” had increased to 13% of total land area.   In the Northeast of the US, forest is expanding on abandoned agricultural land.

Although modern agricultural methods use pesticides and fertilizer, The Economist cites two studies that report net benefit of these techniques to the environment compared to traditional methods.  That claim probably deserves more scrutiny.  We wonder, for example, to what extent our ignorance of the long-term effects of the use of synthetic chemicals made it possible to reach that conclusion.

Greater prosperity also creates leisure time and with it a demand for recreation in nature, resulting in an appreciation of nature.  This respect for nature has also promoted a less utilitarian attitude toward animals.  Animals are no longer viewed as the servants of humans.  Rather they are widely considered our neighbors in the environment in prosperous countries.  This changing attitude toward nature has produced many Non-Governmental Organizations that advocate for the preservation of land and the welfare of the plants and animals that live there. 

Brazil is a case in point because its prosperity is more recent than our own.  Its appreciation of its rainforests is quite new.  Deforestation in the Brazilian Amazon has declined from 28,000 sq kilometers in 2004 to less than 5,000 sq kilometers last year.  The attitude toward the value of the tropical forest has changed and the government’s new regulatory tools reflect that change. 

More prosperous countries are also usually more peaceful.  Wars and conflict often harm the environment, as well as its occupants.  For similar reasons, governments are usually more effective in prosperous countries.  Without competent government, environmental regulations are useless.

Do the facts fit the theory?

Extinction is considered the final test of the preservation of biodiversity.  So, have the rates of extinction decreased as many countries have become more prosperous?  The Economist tells us they have. 

First we must acknowledge our imperfect knowledge of extinction rates because we have identified a small fraction of the total number of species on our planet.  We have identified more of the large species of animals than we have of smaller species such as bacteria and microbes.  So trends in extinctions rates are easier to identify amongst vertebrates, especially birds for which detailed records are more available. 

The moa was a huge flightless bird that was hunted to extinction by Polynesians when they occupied New Zealand.
The moa was a huge flightless bird that was hunted to extinction by Polynesians when they occupied New Zealand.

Around 10,000 bird species have been identified.  Some extinctions are an inevitable result of natural selection, considered the “background” rate of extinction, which is estimated for birds to be about one extinction per century.  Bird extinctions attributed to man are exemplified by the disappearance of approximately 1,000 bird species on islands after they were occupied by Polynesians, which is at least 100 times above the background rate of extinction. 

The extinction rate for birds has decreased considerably in recent times.  Nine species of birds are known to have become extinct during the period 1980 to 2000.  Given our imperfect knowledge of all species, there may be extinctions that have not been noticed and recorded. 

The Economist article mentions the potential for climate change to accelerate rates of extinction.  In our opinion, its optimistic view of the future of biodiversity does not adequately account for that threat.  We attribute that to the viewpoint of the publication, which tends to support economic development by emphasizing its benefits more than its costs. 

The lesson for us in The Economist article is that climate change is the biggest threat to biodiversity.  As long as we continue to turn a blind eye to its causes, we should expect an acceleration of extinction rates in the future.  Eradicating non-native plant species is a diversion from this task.  If non-native plant species are better adapted to a changing climate, they are more likely to support the long-term survival of wildlife.

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(1)    “Special Report:  Biodiversity,” The Economist, September 14-20, 2013.

“Ecological Restoration and Environmental Change”

Green Oaks, Knox College
Green Oaks, Knox College

Restoration and Environmental Change:  Renewing Damaged Ecosystems was written by Stuart Allison.  He is Professor of Biology and Director of Green Oaks Field Study Center at Knox College in Illinois.  His perspective on ecological restorations is unique because he is both a scientist and actively engaged in ecological restoration. 

There is a predictable tension between applied and theoretical science.  Ecology is particularly susceptible to this tension because its application is usually considered the immediate goal of the theoretical science that is intended to inform and guide it.  Therefore, we were very interested in Professor Allison’s viewpoint and we were intrigued by the suggestion of his title that his book would take into consideration the rapidly changing environment.

Although the restoration goal at Green Oaks is the re-creation of the tall grass prairie that is the historical landscape, Allison’s Ph.D. degree from UC Berkeley in Integrative Biology suggested that he is also familiar with our local ecology in the San Francisco Bay Area.  In fact, he mentions our controversy regarding the desire of native plant advocates to eradicate eucalyptus in California and he uses it to illustrate his opinion of novel ecosystems.

“When I was a graduate student at the University of California, Berkeley there was (and still is) a magnificent grove of blue gum (Eucalyptus globulus) outside of the Life Sciences Building.  It was rumored that they were some of the tallest blue gums in the world, growing so tall because they lacked any herbivores and diseases.  Eucalyptus trees grow beside roads all along California’s coastal highways and in the inland valleys of the coast ranges.  In fact, I cannot imagine California without eucalyptus trees.  But, of course, eucalyptus are not native to California–the first eucalyptus was introduced to California by Australian miners coming to the Gold Rush in the 1850s.  Today eucalyptus are so well established that many people think they are native to California, and even if they know they are not native, they don’t want to see them removed because to them, like me, eucalyptus are a central part of their experience of California.  Some people also fear that removal of eucalyptus will lead to erosion on steep hillsides and a decline in biodiversity.  In contrast, native plant enthusiasts in California would love to see eucalyptus permanently removed.  The dominance of eucalyptus in California is hardly unusual for a novel ecosystem, but it stands out because the trees came from Australia and because they are so striking in appearance and aroma that they can’t be missed.” (1)

Professor Allison then acknowledges that some scientists are now interested in and respectful of novel ecosystems such as the eucalyptus forest.  However, he is worried “that novel ecosystems will lead to a homogenized world in which the same species…are found everywhere.”   That debate is not the central theme in his book.  His primary objective is to take the pulse of his colleagues in ecological restoration and report the changes in their objectives in the past 20 years, given the rapid changes that have occurred in the environment.

What is the goal of ecological restoration?

The Society for Ecological Restoration (SER) is the professional organization recognized by most restorationists.  Its Policy Working Group claims that “an ecosystem is fully restored and the project has been completed when the restoration ‘contains sufficient biotic and abiotic resources to continue its development without further assistance or subsidy.’”

Annual Prairie Burn, Green Oaks, Knox College
Annual Prairie Burn, Green Oaks, Knox College

Professor Allison tells us that the restoration in which he has been engaged for over 20 years will never achieve that standard:  “The tall grass prairie and savanna restorations I work with are all based on a return to historical pre-Euro-American disturbance, but all require perpetual management and human intervention to maintain them on the desired ecological trajectory.  Without regularly applied fire, those ecosystems would soon become dominated by many woody species and grow into a woodland lacking prairie or savannah characteristics.”  Professor Allison describes the annual “Prairie Burn” at Green Oaks which is considered an important social event by students at Knox College.

This is one of many ironies about ecological restorations.  Many projects are attempting to re-create an historical landscape at a specific period of time, which was not the result of natural succession.  In the case of grassland prairie, it was largely the result of periodic fires set by Native Americans.  Left to its natural devices, grassland would soon be “invaded” by shrubs and over time it would become a forest if soil and climate conditions were suitable.  In that sense, it is an artificial landscape, as unnatural as any manmade garden.  That the humans who created that historical landscape were indigenous, as opposed to European settlers, seems to us a meaningless, legalistic quibble.

The “field of dreams” theory

Most restoration projects focus almost entirely on plants.  Little explicit attention is paid to the animals that are the desirable inhabitants of the restoration.  Restorationists believe that if the habitat is made available, the animals will quickly follow.  This is the “field of dreams” theory, i.e., if we build it, the animals will come.   This is magical thinking.

Restoration projects rarely monitor the results of their projects sufficiently to test this theory.  In the San Francisco Bay Area, native plant advocates claim there are more birds and animals occupying restoration sites, but these are anecdotal observations that cannot be verified.  Nor do they seem credible to skeptics of the projects, who often think the habitat that has been eradicated actually supported more wildlife. 

Evolving goals of restoration projects

Here in the San Francisco Bay Area we have observed the changing objectives of ecological restorations.  Over fifteen years ago, local projects were touted as “sustainable.”  The public was told that once restored to historical equilibrium conditions, the projects would be capable of sustaining themselves without further resources. 

Comparson of pesticides used by San Francisco's "Natural Areas Program" compared to landscaped areas of San Francisco's parks
Comparson of pesticides used by San Francisco’s “Natural Areas Program” compared to landscaped areas of San Francisco’s parks. Photo courtesy of SF Forest Alliance.

We no longer hear that claim.  Now we are told that our “natural areas” must be managed in perpetuity.  More herbicides are used in San Francisco’s “natural areas” than landscaped portions of the parks, with the exception of a professional tournament golf course.  And if we want the animals that historically occupied those areas, they must be reintroduced, using labor-intensive methods.

Professor Allison observes the same “mission creep” amongst his colleagues.  The goal of replicating an historical landscape is no longer the dominant theme of ecological restorations.  Now the goal is more commonly defined in terms of increasing “biodiversity” and improving “ecological functions.”

New buzz words

If the new goal of ecological restorations is greater biodiversity and improved ecological functions, it seems reasonable to ask what these terms mean.  Unfortunately, we were unable to find the answer to that question in Professor Allison’s book.  Those terms are used as though their meanings are intuitively obvious.  They are not.  These terms are jargon that has little intrinsic meaning and they probably mean different things to different people.

When scientific studies quantify biodiversity, they count species of both native and non-native plants and animals.  Since there are now far more species of non-native plants and animals and far fewer extinctions of native plants and animals, biodiversity has increased virtually everywhere in the world.  So, as far as science is concerned, how could a restoration project that eradicates all non-native species result in greater biodiversity?

Obviously native plant advocates are defining the word “biodiversity” differently than traditional science.  Native plant advocates seem to define biodiversity as exclusively native.  Furthermore, the nativist ideology believes that the mere existence of non-native plants and animals will inevitably result in the extinction of native plants and animals.  There is little scientific evidence to support this assumption.  Few extinctions have been attributed to the existence of non-native plants and no extinctions blamed on non-native plants have occurred in the continental United States.

The term “ecological functions” is even more mysterious as it relates to ecological restorations.  It could mean almost anything:  production of biomass, soil composition, photosynthesis, carbon sequestration and storage, nutrient cycling, fire regime, hydrologic cycle, etc. 

Professor Allison does not provide us with his definition of this term, so we will make an assumption based on our knowledge of ecological scientific literature.  We told our readers about a study in Hawaii which compared native and non-native forests with respect to the ecological functions they are performing.  In that study, three such functions were measured and reported:  carbon sequestration, production of biomass, and nutrient cycling.  The study concluded that non-native forests were performing these ecological functions as well as native forests. 

We can also compare treeless grassland prairie with a native or non-native forest with respect to those ecological functions.  Forests—whether native or non-native– will fulfill these and other functions at least as well as the grassland prairie.  If we add the factor that the grassland prairie must be burned annually to maintain it, clearly the grassland prairie is an ecological deficit because it releases pollutants and greenhouse gases into the atmosphere when it is burned.

The moving target

The goals of ecological restoration are a moving target.  The original goals of re-creating an historical landscape that would be sustainable without continual maintenance are now widely acknowledged to be unrealistic. 

The new goals are equally elusive.  The new goals are described in obscure ways that will be impossible to measure or evaluate.  That suits the purposes of native plant advocates perfectly.  They can continue to do whatever they want and the public can’t hold them accountable because the public is not provided with a practical method of measuring success or failure.  

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(1)    Stuart K. Allison, Ecological Restoration and Environmental Change:  Renewing Damaged Ecosystems, Routledge, UK, USA, Canada, 2012