Category: Ecology

Environmental Impact Report for the Natural Areas Program is based on a HUGE mistake!

There is a HUGE mistake in the Environmental Impact Report (EIR) for the Natural Areas Program (NAP), which will fundamentally alter the public’s perception of the EIR.

The EIR says on page 2 in the Summary that the “Maximum Restoration Alternative” is the “Environmentally Superior Alternative.”  The statement on page 2 is WRONG!  The “Maintenance Alternative” is the “Environmentally Superior Alternative,” as explained on page 525-526 of the EIR.

When we first informed our readers of the publication of the Environmental Impact Report (EIR) for the Natural Areas Program (NAP) on September 9, 2011, we also announced that the EIR considers the “Maximum Restoration Alternative” the “Environmentally Superior Alternative.”  The “Maximum Restoration Alternative” proposes an aggressive expansion of the NAP that will destroy more trees, require more herbicide use, close more trails and other recreational access, and permit NAP to plant more legally protected species that could require more restrictions in the future.   When we announced this proposed expansion of the program, we were reporting what the EIR says on page 2 in the Summary of the EIR. 

So, we repeat, the statement on page 2 is wrong.  The “Maximum Restoration Alternative” is NOT the “Environmentally Superior Alternative.”  The “Environmentally Superior Alternative” is the “Maintenance Alternative.”  The correct statement does not appear in the EIR until the very end of the document:

“The Maximum Recreation and Maintenance Alternatives are the environmentally superior alternatives because they have fewer unmitigated significant impacts than either the proposed project or the Maximum Restoration Alternative. Between the Maximum Recreation Alternative and the Maintenance Alternative, the Maintenance Alternative would be the environmentally superior alternative for two reasons. While the two alternatives have the same number of significant and unavoidable impacts under CEQA, the Maintenance Alternative has fewer potential environmental effects than the Maximum Recreation Alternative. First, the Maintenance Alternative would not create new trails, the construction of which could result in impacts to sensitive habitats and other biological resources. Second, over time the Maximum Recreation Alternative would result in Natural Areas with less native plant and animal habitat and a greater amount of nonnative urban forest coverage. The Maintenance Alternative, on the other hand, would preserve the existing distribution and extent of biological resources, including sensitive habitats. For these reasons, the Maintenance Alternative is the environmentally superior alternative.” (EIR, page 525-526) (emphasis added)

The contradiction between what appears on page 2 of the EIR and page 526 was pointed out to the staff of the Planning Department responsible for managing the public comment period and certification of the EIR.  That staff member confirmed that the statement on page 2 is wrong and the statement on page 526 is correct.  However, she refused to correct the error until the public comment period is over and the Final Environmental Impact Report is published.

Unfortunately, this mistake and the refusal to correct it before the public comment period is complete will jeopardize the fairness of the process.  Native plant advocates are already recruiting their speakers for the public hearing by the Planning Commission on October 6, 2011, and the written comments which are due on October 17, 2011*.  They are urging their supporters to advocate for the “Maximum Restoration Alternative” and they are incorrectly informing them that this is the “Environmentally Superior Alternative.”  We have no reason to believe that they are aware of the mistake on page 2 of the EIR.  They are probably sincere in their belief that the “Maximum Restoration Alternative” is the “Environmentally Superior Alternative.”  Few readers are likely to read the entire EIR and will therefore be unaware of the mistake on page 2.

This mistake will mislead the public into supporting the “Maximum Restoration Alternative” that expands the destructive and restrictive aspects of the Natural Areas Program.  Furthermore, and perhaps more importantly, this expansion is NOT legal because it violates the requirements of the California Environmental Quality Act (CEQA), which requires that the “Environmentally Superior Alternative” have the least negative impact on the environment of all proposed alternatives:

“§21002.  APPROVAL OF PROJECTS; FEASIBLE ALTERNATIVE OR MITIGATION MEASURES

The Legislature finds and declares that it is the policy of the state that public agencies should not approve projects as proposed if there are feasible alternatives or feasible mitigation measures available which would  substantially lessen the significant environmental effects of such projects,  and that the procedures required by this division are intended to assist public agencies in systematically identifying both the significant effects of proposed projects and the feasible alternatives or feasible mitigation measures which will avoid or substantially lessen such significant effects.”  CEQA Guidelines, page 2 (emphasis added)

Pardon our paranoia….

 This is a huge mistake which could profoundly prejudice the public to support the “Maximum Restoration Alternative” which proposes an expansion of the Natural Areas Program.  We ask these rhetorical questions:

  •  Who wrote page 2 of the EIR, which incorrectly identifies the “Maximum Restoration Alternative” as the “Environmentally Superior Alternative” and why?
  • Why does the Planning Department refuse to correct this error before the public comment is complete?

If you attend the public hearing on October 6, 2011, please inform the Planning Commission of this error and write by the deadline of October 17, 2011*, in support of the “Maintenance Alternative” which will do less damage to the environment than the proposed project and the other proposed alternatives.  Here are the details about the opportunities for public comment:

“A public hearing on this Draft EIR and other matters has been scheduled by the City Planning Commission for October 6, 2011, in Room 400, City Hall, 1 Dr. Carlton B. Goodlett Place, beginning at 1:30 p.m. or later. (Call 558‐6422 the week of the hearing for a recorded message giving a more specific time.)”

 “Public comments will be accepted from August 31, 2011 to 5:00 p.m. on October 17, 2011^. Written comments should be addressed to Bill Wycko, Environmental Review Officer, San Francisco Planning Department, 1650 Mission Street, Suite 400, San Francisco, CA 94103. Comments received at the public hearing and in writing will be responded to in a Summary of Comments and Responses document.”

*[ETA:  The deadline for written comments has been extended to October 31, 2011, at the request of the Planning Commission.]

The Healthy Trees of San Francisco

The San Francisco Natural Areas Program (NAP) plans to destroy thousands of healthy trees in San Francisco’s parks.  The Draft Environmental Impact Review (EIR) for NAP’s destructive plan reaches the bizarre conclusion that removing thousands of trees will have no significant impact on the environment.   This conclusion is based on several fictional premises.  In a previous post we examined the fictional claim that all the trees that will be removed will be replaced within the natural areas by an equal number of trees that are native to San Francisco.  In this post we will examine another of the fictional premises:  that only dead, dying, hazardous, or unhealthy trees will be removed.

We have many reasons to challenge the truth of the claim that only dead, dying, hazardous or unhealthy trees will be removed:

  • The management plan for the Natural Areas Program tells us that young non-native trees under 15 feet tall will be removed from the natural areas.  By definition these young trees are not dead or unhealthy because they are young and actively growing.
  • The management plan has not selected only dead, dying, hazardous trees for removal.  Trees have been selected for removal only in so far as they support the goal of expanding and enhancing areas of native plants, especially grasslands and scrub.
  • The predominant non-native tree in San Francisco, Blue Gum eucalyptus lives in Australia from 200-400 years, depending upon the climate.(1)  In milder climates, such as San Francisco, the Blue Gum lives toward the longer end of this range. 
  • However, there are many natural predators in Australia that were not imported to California. It is possible that the eucalypts will live longer here:  “Once established elsewhere, some species of eucalypts are capable of adjusting to a broader range of soil, water, and slope conditions than in Australia…once released from inter-specific competitions and from native insect fauna…”(2)
  • The San Francisco Presidio’s Vegetation Management Plan reports that eucalypts in the Presidio are about 100 years old and they are expected to live much longer: “blue gum eucalyptus can continue to live much longer…”(3)
  • The Natural Areas Program has already destroyed hundreds of non-native trees in the past 15 years.  We can see with our own eyes, that these trees were not unhealthy when they were destroyed.

How have mature trees been selected for removal?

The EIR wants us to believe that only dead, dying, hazardous trees will be removed from the natural areas.  This claim is contradicted by the management plan that the EIR is claiming to evaluate.  Not a single explanation in the management plan for why specific trees over 15 feet tall have been selected for removal is based on the health of the trees.  Trees less than 15 feet tall will also be removed, but are not counted by the management plan.

  • Lake Merced:  The explanation for removing 134 trees is “To maintain and enhance native habitats, it is necessary to selectively remove some trees.”
  • Mt. Davidson:  The explanation for removing 1,600 trees is: “In order to enhance the sensitive species habitat that persists in the urban forest understory and at the forest-grassland ecotone, invasive blue gum eucalyptus trees will be removed in select areas. Coastal scrub and reed grass communities require additional light to reach the forest floor in order to persist “
  • Glen Canyon:  The explanations for removing 120 trees are:  “to help protect and preserve the native grassland” and “to increase light penetration to the forest floor”
  • Bayview Hill:  The explanation for removing 505 trees is:  “In order to enhance the sensitive species habitat that persists in the urban forest understory and at the forest-grassland ecotone, invasive blue gum eucalyptus trees will be removed in select areas.”
  • McLaren:  The explanation for removing 805 trees is:  “In order to enhance the sensitive species habitat that persists in the urban forest understory and at the forest-scrub-grassland ecotone, invasive trees will be removed in select areas. Coastal scrub and grassland communities require additional light to reach the forest floor in order to persist.”
  • Interior Greenbelt:  The explanation for removing 140 trees is:  “In order to enhance the seasonal creek and sensitive species habitat that persists in the urban forest understory, invasive blue gum eucalyptus trees will be removed in select areas.”
  • Dorothy Erskine:  The explanation for removing 14 trees is:  “In order to enhance the grassland and wildflower community, removal of some eucalyptus trees is necessary.”

In not a single case does the management plan for the Natural Areas Program corroborate the claim made in the EIR that only dead, dying, diseased, or hazardous trees will be removed.  In every case, the explanation for the removal of eucalypts is that their removal will benefit native plants, specifically grassland and scrub.  The author of the EIR has apparently not read the management plan or has willfully misrepresented it. 

The track record of tree removals in the natural areas

Although it’s interesting and instructive to turn to the written word in the management plan for the Natural Areas Program to prove that the EIR is based on fictional premises, the strongest evidence is the track record of tree removals in the past 15 years.  As always and in every situation, actions speak louder than words.

Hundreds of trees have been removed in the natural areas since the Natural Areas Program began 15 years ago.  We’ll visit a few of those areas with photographs of those tree removals to prove that healthy, young non-native trees have been destroyed.  This track record predicts the future:  more healthy young trees will be destroyed in the future for the same reason that healthy young trees were destroyed in the past, i.e., because their mere existence is perceived as being a barrier to the restoration of native grassland and scrub.

Girdled trees, Bayview Hill, 2010
  • The first tree destruction by the Natural Areas Program and its supporters took the form of girdling about 1,000 healthy trees in the natural areas about 10 to 15 years ago.  Girdling a tree prevents water and nutrients from traveling from the roots of the tree to its canopy.  The tree dies slowly over time.  The larger the tree, the longer it takes to die.  None of these trees were dead when they were girdled.  There is no point in girdling a dead tree.

    One of about 50 girdled trees on Mt. Davidson, 2003
  • Many smaller trees that were more easily cut down without heavy equipment were simply destroyed, sometimes leaving ugly stumps several feet off the ground.

    Bayview Hill, 2002
  • About 25 young trees were destroyed on Tank Hill about 10 years ago.  The neighbors report that they were healthy trees with trunks between 6″ to 24″ in diameter and therefore fairly young trees.  The trees that remain don’t look particularly healthy in the picture because they were severely limbed up to bring more light to the native plant garden for which the neighboring trees were destroyed.  The neighbors objected to the removal of the trees that remain.  The Recreation and Park Department agreed to leave them until they were replaced by native trees.  Only 4 of the more than two dozen live oaks that were planted as replacements have survived.  They are now about 36″ tall and their trunks are about 1″ in diameter. 

    Tank Hill, 2002
  • About 25 young trees were destroyed in 2004 at the west end of Pine Lake to create a native plant garden that is now a barren, weedy mess surrounded by the stumps of the young trees that were destroyed.

    Pine Lake "Natural Area" 2011
  • About 25 trees of medium size were destroyed at the southern end of Islais Creek in Glen Canyon Park about 6 years ago in order to create a native plant garden. 
  • Many young trees were recently destroyed in the natural area called the Interior Greenbelt.  These trees were destroyed in connection with the development of a trail, which has recently become the means by which the Natural Areas Program has funded tree removals with capital funding.

    Interior Greenbelt Natural Area, 2010. Courtesy SaveSutro

There was nothing wrong with any of these trees before they were destroyed.  Their only crime was that they were not native to San Francisco.  There are probably many other trees that were destroyed in the natural areas in the past 15 years.  We are reporting only those removals of which we have personal knowledge.

If you care about the trees of San Francisco….

If you care about the trees of San Francisco, please keep in mind that the public will have an opportunity to comment on the proposal to remove thousands of trees in the city’s parks.  There will be a public hearing on October 6, 2011, and the deadline for submitting a written comment is October 17, 2011*.  Details about how to comment are available here.

*[ETA:  The deadline for written comments has been extended to October 31, 2011, at the request of the Planning Commission.]

(1) Jacobs, Growth Habits of the Eucalyptus, 1955, page 67

(2) Doughty,  The Eucalyptus, 2000, page 6

(3) San Francisco Presidio’s Vegetation Management Plan, page 28

Destroying the Trees of San Francisco

The San Francisco Natural Areas Program (NAP) plans to destroy thousands of trees in San Francisco’s parks.  The Draft Environmental Impact Report (EIR) for NAP’s destructive plan reaches the bizarre conclusion that removing thousands of trees will have no significant impact on the environment.   This conclusion is based on several fictional premises.  In this post we will examine one of those premises:   that all the trees that are removed will be replaced within the natural areas by an equal number of trees that are native to San Francisco.

The EIR supports this fictional premise by falsely reducing the number of trees that will be removed by:

  • Not counting trees less than 15 feet tall, despite the fact that the US Forest Service survey of San Francisco’s urban forest reports that the trunks of most (51.4%) trees in San Francisco are less than 6 inches in diameter at breast height, the functional equivalent of trees less than 15 feet tall.
  • Not counting the hundreds of trees that were destroyed prior to the approval of the NAP management plan at Pine Lake, Lake Merced, Bayview Hill, Glen Canyon parks, etc.
  • Not counting tree removals proposed by the “Maximum Restoration Alternative” which the EIR says is the “Environmentally Superior Alternative.” [ETA: The Planning Department later admitted that this is a mistake in the EIR.  The “Maintenance Alternative” is the “Enviromentally Superior Alterantive.”]

However, even artificially reducing the number of tree removals does not make “one-to-one” replacement a realistic goal.

The natural history of trees in San Francisco

The primary reason why we know that it will not be possible to grow thousands more native trees in the natural areas in San Francisco is that there were few native trees in San Francisco before non-native trees were planted by European settlers in the late 19th century.  San Francisco’s “Urban Forest Plan” which was officially adopted by the Urban Forestry Council in 2006 and approved by the Board of Supervisors describes the origins of San Francisco’s urban forest as follows:

“No forest existed prior to the European settlement of the city and the photographs and written records from that time illustrate a lack of trees…Towards the Pacific Ocean, one saw vast dunes of sand, moving under the constant wind.  While there were oaks and willows along creeks, San Francisco’s urban forest had little or nothing in the way of native tree resources.  The City’s urban forest arose from a brief but intense period of afforestation, which created forests on sand without tree cover.”

San Francisco in 1806 as depicted by artist with von Langsdorff expedition. Bancroft Library

The horticultural reality of trees native to San Francisco

More importantly, the reality is that even if we want to plant more native trees in San Francisco, they will not grow in most places in San Francisco.  We know that for several reasons: 

  • There are few native trees in San Francisco now.  According to the US Forest Service survey of San Francisco’s urban forest only two species of tree native to San Francisco were found in sufficient numbers to be counted in the 194 plots they surveyed:  Coast live oak was reported as .1% (one-tenth of one percent) and California bay laurel 2.1% of the total tree population of 669,000 trees.
  • The city of San Francisco maintains an official list of recommended species of trees for use by the Friends of the Urban Forest and the Department of Public Works.  The most recent list categorizes 27 species of trees as “Species that perform well in many locations in San Francisco.”  There is not a single native tree in that category.  Thirty-six tree species are categorized as “Species that perform well in certain locations with special considerations as noted.”  Only one of these 36 species is native to San Francisco, the Coast live oak and its “special considerations” are described as “uneven performer, prefers heat, wind protection, good drainage.”  The third category is “Species that need further evaluation.”  Only one (Holly leaf cherry) of the 22 species in that category is native to San Francisco. 
  • Finally, where native trees have been planted by NAP to placate neighbors who objected to the removal of the trees in their neighborhood parks, the trees did not survive.

Will NAP plant trees that won’t survive?

Given what we know about the horticultural requirements of the trees that are native to San Francisco, what are we to think of the claim that all non-native trees removed by the Natural Areas Program will be replaced by native trees?  Is there any truth to this claim?  Will native trees be planted that won’t survive?  Or will they just not plant the trees that they claim will be planted?

We turn to the management plan for the Natural Areas Program for the answer to this question.  In fact, the management plan proves that NAP has no intention of planting replacement trees for the thousands of trees they intend to destroy.  The “Urban Forestry Statements” in Appendix F of the management plan contain the long-term plans for the natural areas in which trees will be destroyed.  All but one of these specific plans is some variation of “conversion of some areas of forest to scrub and grasslands.”  The exception is Corona Heights for which the plans are “converted gradually to oak woodland.”  The Corona Heights natural area is 2.4 acres, making it physically impossible to plant thousands of oaks in that location.

NAP plans to destroy 1,600 trees over 15 feet tall on Mt. Davidson and more if the EIR is approved.

  

Putting the magnitude of the proposed tree removals into perspective

It isn’t easy to confront public policies.  We all have better things to do.  So, before we leave this issue, let’s consider the magnitude of the loss of thousands of trees in San Francisco.  We turn to the survey of San Francisco’s urban forest by the US Forest Service to put the proposed tree removals into perspective:

  • There are only 669,000 trees in San Francisco, with a tree cover of only 11.9% of the land.  Of the 14 cities in the US reported by this survey, only Newark, New Jersey has a smaller tree canopy, covering 11.5% of the land.
  • Most of these trees are small:  51.4% have trunk diameters of less than 6” at breast height.
  • The highest densities of trees are found in San Francisco’s open spaces, such as parks.
  • The trees and shrubs of San Francisco remove 260 tons of air pollutants (CO, NO₂ , O₃, PM₁₀, SO₂) per year
  • The trees of San Francisco now store 196,000 tons of carbon.  Stored carbon is released into the atmosphere when trees are destroyed and as they decay as chips or logs on the ground.
  • In San Francisco, the blue gum eucalyptus stores and sequesters the most carbon (approximately 24.4% of the total accumulated carbon stored and 26.4% of annual rate of carbon sequestered).  Most of the trees that have been destroyed in the past and will be destroyed in the future by NAP are blue gum eucalyptus. 

If you care about the trees of San Francisco, please keep in mind that the public will have an opportunity to comment on the proposal to remove thousands of trees in the city’s parks.  There will be a public hearing on October 6, 2011, and the deadline for submitting a written comment is October 17, 2011*.  Details about how to comment are available here.

*[ETA:  The deadline for written comments has been extended to October 31, 2011, at the request of the Planning Commission.]

Environmental Impact Report of Natural Areas Program proposes aggressive expansion

Fifteen years after San Francisco’s Natural Areas Program (NAP) began operation and 5 years after its management plan was approved, the Draft Environmental Impact Report (EIR) has finally been published.  We will briefly summarize the history of NAP, describe the plans as they were approved in 2006, and conclude with a comparison between those plans and the proposal in the EIR to aggressively expand NAP.

The Management Plan for the Natural Areas Program

In 1995 the Recreation and Park Commission approved the designation of 31“natural areas” in parks managed by the city of San Francisco. This designation committed 25% of the city’s park acreage in San Francisco, 33% including the city of Pacifica to the Natural Areas Program.  

Most park visitors were unaware of this designation until 5 years later when they finally had access to a draft of the management plan after a lengthy battle to make it available.  At that point, many park visitors could see where the Natural Areas Program was headed and many of them reacted negatively to the prospect of the destruction of non-native trees and restrictions on recreational access in popular, heavily visited parks.

The result of the long debate with the public was a revised management plan that separated the natural areas into three “management areas.”  These management areas (MAs) set priorities for the restoration of parkland to native plants:  MA-1 was the highest priority, MA-2 the second priority, and MA-3 the lowest priority.  The appeal of these priorities to critics of NAP was the commitment that there would be no tree removals in the MA-3 areas and that no legally protected species would be planted or reintroduced there, which might require further access restrictions in the future.  Forty-two percent of the total 1,080 acres of natural areas was designated as MA-3.

The management plan* was approved in 2006, after two days of public hearings at which about 200 public comments were heard by the Recreation and Park Commission.  Supporters of NAP outnumbered critics of the program.  The main message of the critics of the program was that the acreage committed to natural areas should be reduced to places in which native plants existed, which would not include acreage designated MA-3.

There were two trivial caveats to the approval of the program:  defining the circumstances under which cats could be removed from the natural areas and specifying that tree removals must be done by the Urban Forestry Division of the Recreation and Park Department (RPD).  These are some of the main features of the approved management plan:

  • Tree removals.  18,500 trees over 15 feet tall were designated for removal in MA-1  and   MA-2 areas.   In addition, non-native trees under 15 feet tall would be removed in these areas, but were not quantified because the plan did not define them as “trees”
  • Trails.  10.3 miles of trails were designated for closure in these areas.  That represented 26% of all trails in the natural areas.
  • Dog Play Areas are those areas in parks that have been officially designated for off-leash recreation.  The NAP management plan identified several dog play areas that would be monitored for possible closure in the future if necessary to protect native plants.  Those dog play areas were in Bernal Hill, McLaren and Lake Merced parks. 
  • Golf Course at Sharp Park will be reconfigured to accommodate populations of two endangered species.

The Environmental Impact Report of the Natural Areas Program

Five years after the approval of the management plan, the Environmental Impact Report (EIR) has finally been published.  The EIR identifies 4 alternatives to move forward with the implementation of the plan. The EIR identifies the “Maximum Restoration Alternative” as the “Environmentally Superior Alternative” described as follows:

“This alternative seeks to restore native habitat and convert nonnative habitat to native habitat wherever possible throughout the Natural Areas, including all management areas.”

[ETA:  This article has been updated by a more recent post which reports that a mistake has been found in the Draft Environmental Impact Report (DEIR):  The “Maximum Restoration Alternative” is not the “Environmentally Superior Alternative” as the DEIR claims on page 2.  The “Maintenance Alternative” is the “Environmentally Superior Alternative” as the DEIR says on page 526.  The mistake on page 2 has been reported to the Planning Department.  The Planning Department has acknowledged the error on page 2 and has made a written commitment to correct the error in the Final Environmental Impact Report.  Unfortunately, this correction will not be made until the public comment period is over.]

In other words, the preferred alternative would do away with the priorities identified in the management plan and treat all three management areas the same.  These are the specific implications of this proposal as described by the EIR:

  • Trees.  Non-native trees would also be removed in the MA-3 areas.  The number of trees over 15 feet tall that will be removed will exceed 18,500, but the EIR does not quantify how many trees will be removed.
  • Trails.  More trails would be closed in the MA-1 and MA-2 areas, but the EIR is not specific about how many miles of trail will be closed.
  • Dog Play Areas.  All dog play areas in MA-1 and MA-2 areas would be closed.  This will close the dog play areas in Buena Vista and Golden Gate (Southeast) parks and what little remained of McLaren (Shelley Loop) and Bernal Hill after the closures mandated by the management plan.  Dog play areas in MA-3 areas will be monitored and closed in the future if necessary to protect native plants.  The EIR predicts that all of these closures in addition to the anticipated closures of GGNRA properties to off-leash dogs will result in heavier usage of the dog play areas that remain.
  • Golf Course at Sharp Park would be further reduced by expanded habitat for endangered species.
  • Other access restrictions.  Legally protected species will be introduced in MA-3 areas, which may require further restrictions on access in the future.

The other alternatives identified in the EIR are:

  • “No Project Alternative – Under this alternative, the SFRPD would continue with the management activities authorized under the 1995 management plan.”  This alternative will close the dog play areas that were monitored since the management plan was approved in 2006: the Mesa at Lake Merced, portions of Bernal Hill and McLaren (Shelley Loop).
  • “Maximum Recreation Alternative – This alternative seeks to restore and improve recreational access to the Natural Areas wherever it does not interfere with the continued existence of native species and federally or state-listed sensitive species.”
  • “Maintenance Alternative – This alternative seeks to maintain the current distribution of native and nonnative habitat and species throughout the Natural Areas.  Under this alternative there would be no conversion of nonnative habitat to native habitat; other features of the Natural Areas would be retained.”

Rewarding Failure

Park visitors who have been watching the restoration efforts of the Natural Areas Program for the past 15 years might be surprised that NAP apparently wishes to expand its restoration efforts.  Repeated clearing of non-native plants and planting of native plants has been spectacularly unsuccessful.  Here’s a photo history of the effort at Pine Lake in Stern Grove:

One of several clearing and plantings of south shore of Pine Lake, 2003
The results, south shore of Pine Lake, 2011
North shore of Pine Lake, 2003
 
Results, north shore Pine Lake, 2011

If NAP has been unable to successfully restore 58% of acres of natural areas (MA-1 and MA-2) they have been actively working on for the past 15 years, why would they want to expand their empire by adding MA-3 acreage to their agenda, committing them to actively restoring all 1,080 acres of natural areas?  Aren’t they biting off more than they can chew?

Where will the money come from to fund this expanded effort?

Although NAP and its many supporters believe that this lack of success is because they haven’t been adequately funded, the NAP staff is one of the only divisions in the Recreation and Park Department that hasn’t been cut in the past 10 years.  While other gardeners have been laid off, the NAP staff has remained the same size.  How many gardeners will it take to expand their restoration efforts to the MA-3 areas as the EIR proposes?  Remember that the MA-3 areas are 42% of the total NAP acreage.  Will NAP be given a 42% increase in their staff?  One wonders where the money for such an increase in staff would be taken from.

How much more herbicide will be used in this expanded effort?

Will a 42% increase in actively management NAP acreage require more herbicide use?  The Natural Areas Program applied herbicides to the so-called “natural areas” 69 times in 2010. Most of those applications were of the most toxic herbicide (Garlon) for which the Natural Areas Program was granted exceptional permission to use by the Department of the Environment.  How much more herbicide must be used by NAP if they actively manage the MA-3 areas?  The EIR is curiously silent on this question.

Public Comment Opportunities

The public will have two opportunities to comment on the EIR and its “environmentally superior alternative” which will aggressively expand the restoration efforts of the Natural Areas Program, require more tree removals and recreational access restrictions, probably cost much more, and probably increase the use of herbicides.

  • “A public hearing on this Draft EIR and other matters has been scheduled by the City Planning Commission for October 6, 2011, in Room 400, City Hall, 1 Dr. Carlton B. Goodlett Place, beginning at 1:30 p.m. or later. (Call 558‐6422 the week of the hearing for a recorded message giving a more specific time.)”
  • “Public comments will be accepted from August 31, 2011 to 5:00 p.m. on October 17, 2011*. Written comments should be addressed to Bill Wycko, Environmental Review Officer, San Francisco Planning Department, 1650 Mission Street, Suite 400, San Francisco, CA 94103. Comments received at the public hearing and in writing will be responded to in a Summary of Comments and Responses document.”
  • “If you have any questions about the environmental review of the proposed project, please call Jessica Range at 415‐575‐9018.”

*[ETA:  The deadline for written comments has been extended to October 31, 2011, at the request of the Planning Commission.]

If you have an opinion about the expansion of the Natural Areas Program proposed by the Environmental Impact Report  you would be wise to speak/write now.  It is your last opportunity to do so.

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*Type in search box:  Natural Areas Program management plan

Are native species inherently superior to non-native species?

The native plant movement is based on the fundamental assumption that native species of plants and animals are inherently superior to non-native species.  The basis of this assumption seems to vary.  Sometimes the explanation offered is as simple as “the non-native doesn’t belong here.”  It’s not clear what that statement means.  Putting it in the best light, it implies that there is some optimal ecology that is best represented by exclusively native species.  A less generous interpretation would be that non-native plant and animal species are the non-human equivalent of illegal immigrants. 

We will examine this claim of the superiority of native species in the context of bees to make the point that nature is complex and cannot be oversimplified by such a sweeping generalization.

Professor Gordon Frankie, our local expert on the bees of the Bay Area, says that native bees are superior pollinators to the European honeybee.  If that were true, we would consider that a legitimate basis for the judgment that, in this case, the native bee is superior to the non-native bee.  However, the evidence available to us suggests that a comparison of the native to the non-native bee is more complicated.

In considering this question, we will focus on agriculture rather than residential gardens, because agriculture is economically more important and for the same reason more is known about the role of bees in agriculture.

Why would native bees be superior pollinators than non-native bees?

We know of two specific examples of native bees that are more effective pollinators of agricultural crops.  Both cases illustrate the pros and cons of native bees as agricultural pollinators.

Bumblebee on Cotoneaster, Albany Bulb

There are some crops—tomatoes, cranberries, blueberries, eggplants, and kiwi fruits—that are effectively pollinated by native bumblebees (Bombus) because of their unique method of pollination.  This method is called “buzz-pollination” or “sonication” and it is described as “an intense vibration, like a tuning fork being struck, pollen gathered from other flowers literally exploded off Bombus.”(1)

Unfortunately, though its pollination technique is superior, other characteristics of the native bumblebee have limited its usefulness in agriculture.  The crops with which it is most effective produce only pollen.  Therefore, the bumblebee must be provided with an alternate source of nectar to fulfill its dietary needs.(2)  

The bumblebee, like most native bees, is solitary.  It does not live in hives like the social European honeybee.  Therefore, it cannot be transported where and when it is needed, as the honeybee can.  An attempt at a high-tech solution to this limitation ended in disaster:  “In the 1990s, a bumblebee species Bombus occidentalis, was made extinct when experimenting breeders mixed species in Europe and shipped queens back to America.  The queens carried with them an exotic disease that Bombus occidentalis has no immunity for.”   Growers of tomatoes are now “forced to resort to less efficient pollinators.”  (Schacker 2008). 

Another example of a native bee that is a superior pollinator of an agricultural crop is the alkali bee which is the most efficient pollinator of alfalfa, a crop that is essential to the dairy and beef industries.  “Alfalfa flowers…keep their sexual parts hidden, under tension like a spring.  Bees must trip the spring to get at the pollen, and in so doing, they are hit on the head—something honey bees are not particularly fond of.  The alkali bees…don’t mind getting hit on the noggin and will happily pollinate a field of alfalfa.”  (Schacker 2008). 

Native bee approaching nest in ground, Albany Bulb

Unfortunately, the alkali bee, like 85% of native bees in the US, nests in the ground, in particular the alkaline soils of the western US for which it is named.  As cropland in the west expanded, the alkali bee was virtually wiped out by plowing up the ground in which it nested.  A leafcutter bee was imported from Canada as a substitute, but a fungus is now infecting its larvae. (Schacker 2008)

These disadvantages of native bees can be compensated for by providing nesting and nectar sources adjacent to croplands.  These hedgerows must be large enough to provide sufficient nesting opportunities and nectar sources. 

However, such hedgerows do not solve all the potential problems of using native bees as pollinators.  Because the bees are resident year around and cannot be transported, they cannot be removed when the crops are sprayed with pesticides.  And the pesticides are very damaging to the bees.  Therefore, a commitment to providing hedgerows for a resident bee population is also a commitment to organic agriculture, i.e., without using pesticides. 

This is not to say that the honeybees aren’t being adversely affected by the use of pesticides in the crops they are pollinating.  The impact of pesticides on  honeybees would be exacerbated if they were resident when pesticides were applied to the crop.  As it is, the honeybee is being affected by the residues of the pesticides on the crops they pollinate.  This is considered one of the primary reasons for Colony Collapse Disorder of commercial honeybees which has been destroying about one-third of commercial honeybee hives in the past few years.

Unlike most native bees, the European honeybee does not hibernate.  It is therefore available year around to be transported where and when it is needed.  Most native bees hibernate, but not necessarily at the same time.  Different species of native bees hibernate at different times and are therefore available for pollination at different times. 

Most native bees are more selective in their pollination than the European honeybee which is an extreme generalist:  “honeybees have the greatest pollen dietary range…of any known pollinator.” Although there are “only a handful of well-documented cases in North America of truly monolectic bees [a bee that visits only one kind of flower]” (Buchmann 1996), the flower preferences of native bees are narrower than that of the European honeybee.  While some native bees may prefer native plants, honeybees are willing to pollinate both native and non-native plants.  This is important because virtually all of our agricultural crops are non-native.

Native bees are not inherently superior to non-native bees

Honeybee hives, USDA photo

In summary, the European honeybee has several important advantages over native bees as pollinators of agricultural crops:

  • Because the honeybee is a social bee that lives in hives, it can:
    • Be transported where and when it is needed
    • Be removed from the agricultural crop when it is sprayed with pesticides
    • Does not need to be provided with nesting space and an alternate food supply
  • The honeybee is available for pollination services year around because it does not hibernate.
  • The honeybee pollinates a wider range of flowers than most native bees.

While native bees may be more efficient pollinators of residential gardens, there are a number of disadvantages to using native bees for agricultural pollination.  Although many of these obstacles can be overcome with greater use of resources, we cannot agree with the assumption of native plant advocates that native bees are inherently superior to the non-native European honeybee.  As with all sweeping generalizations, the truth is usually more complicated because nature is complex and man’s understanding of it is limited.

(1) Schacker, Michael, A Spring without Bees, Lyons Press, Guilford, Conn, 2008.

(2) Buchmann, S, and Nabhan, G, The Forgotten Pollinators, Island Press, 1996

“Museumification” of our parks separates children from nature

The Berkeley Meadow

We recently published an article about the Berkeley Meadow, a 72-acre fenced pen for native plants and animals.  In response, one of our readers alerted us to a video cartoon about the Berkeley Meadow which we recommend to you.  “Grandpa Takes the Kids to the Plant Zoo” captures the absurdity of this “restoration” project.

The sentiments expressed by the children in this video remind us of an article published in 2004 about similar restoration projects in Chicago and San Francisco.  “Urban Park Restoration and the ‘Museumification’ of Nature” was written by Dr. Paul Gobster after he visited the Bay Area as a visiting professor at UC Berkeley, collaborating with colleagues in landscape architecture.

Dr. Gobster is a social scientist with the US Forest Service, stationed in the Chicago area and the editor of a book* about the restoration movement there.  The restorations in Chicago are similar to those in the San Francisco Bay Area because both places were primarily grassland prior to the arrival of Europeans.   Restorations in both areas therefore require the destruction of most trees.  In the Chicago area, many of the trees are native because of the natural succession of grassland to shrubland and finally to forest.  The fires of Native Americans that sustained the grassland were stopped at the time of settlement.

In “Museumification,” Dr. Gobster expresses his opinion of the restorations in the San Francisco Bay Area and in Chicago:

“…it is my contention that little headway has been made in exploiting the key role urban parks might have in strengthening the ties between nature and culture.  To the contrary, some current attempts at ecological restoration in urban parks may distance people from the experience of nature even further than did earlier naturalistic designs, leading to a form of detached observation not unlike what one might experience in a museum.  Instead of providing a bridge between nature and the city…park restoration can lock nature inside the gates of paradise and leave people on the outside looking in.”

Dr. Gobster is particularly concerned about the impact of “museumification” of parks on children who should be the primary beneficiaries of our parks.  Their earliest experiences with nature may foster a lifelong interest in nature or an alienation from it.

“The wild and weedy nature that existed in many of these urban park areas prior to restoration provided [a setting for unstructured play]…Now displaced by a more ecologically diverse yet more fragile nature, these kinds of activities are discouraged just as they are in more manicured park settings.  Children are much less likely to attain satisfying nature experiences through passive forms of interaction and thus may be disproportionately affected by such changes.  The result of this museumification is that we are creating a significant gap in the spectrum of nature experiences available to urban children precisely at the nearby places where children stand the best chances for getting acquainted with nature.  Thus while striving to achieve authenticity in the restoration of ecosystems we may be sacrificing the authenticity of children’s nature experiences.”

Children discovering nature. NPS photo

In “Grandpa Takes the Kids to the Plant Zoo,” we see that the kids are uninterested in looking at the plants on the other side of the fence.  They ask Grandpa to take them elsewhere so they can play.  Grandpa must also ask them not to touch the few plants within reach because they have been sprayed with herbicides.  The park is not accessible to the kids because it is behind a fence and it has also been sprayed with herbicides, so it’s not a safe place for them to play.  In the East Bay Regional Park District, for example, herbicide use in its restoration projects (AKA “resource management”) increased 300% in 2009.  Herbicides had not been sprayed in the Serpentine Prairie prior to 2009, when it was fenced for “restoration.”  Now it is sprayed with herbicides, mowed, planted, and is due for periodic prescribed burns to prevent its succession to shrubs and subsequently to oak woodland.

When we alienate children from nature, we jeopardize the future of our parks.  If parks are not viewed as useful places, they will not enjoy the support needed to sustain them.  And if nature is not viewed as valuable, we undermine the public’s support for preservation of the environment.  As adults debate the merits of native plant restorations, they should keep in mind the needs of children because the future of our public lands is in their hands and children are unable to speak for themselves in the public policy arena. 

* Gobster & Hull, eds., Restoring Nature, Washington DC, Island Press, 2000

“Mulch Madness” and other restoration mistakes

Thanks to Professor Gordon Frankie (UC Berkeley), we have learned a lot about the bees in the Bay Area.  He has been studying our bees for over 20 years and has made a wealth of interesting information available on his website.

Native bee (Anthrophora urbana) approaching nest in ground at Albany Bulb

Unlike the European honeybee, our native bees are usually solitary.  That is, they do not live in social colonies such as the hives of the European honeybee.   Most (60-70%) California native bees live in small nests in the ground.  Although they may produce enough honey to feed their own young, they don’t store an excess of honey like the honeybee.

Professor Frankie has identified one of the biggest challenges to native bees in urban gardens, “Mulch Madness.” 

“[If] you happen to be one of the many ground-nesting bees that looks for garden sites for digging small tunnels where you will lay your eggs in individually-made brood cells that you will provision with pollen and some nectar, [you have a new problem in urban gardens]…Something has happened in recent years to those favored bare dirt sites that makes your task much harder and oftentimes impossible.  MULCH MADNESS has arrived and has become a highly promoted ‘eco-friendly’ method for suppressing weeds, conserving water, and unknowingly discouraging ground-nesting bees!”

Anyone who is familiar with native plant restorations knows that most are covered in a thick layer of mulch.  When tree removals are required for a restoration, the mulch is usually composed of the chips of the trees that have been cut down.  The projects of UC Berkeley for which UC is applying for FEMA funding (based on its claim that the clear-cutting of all non-native trees will reduce fire hazards) say specifically that the clear-cut areas will be covered with 24 inches of mulch composed of the chips of the destroyed trees.

The UC Berkeley projects also claim that native vegetation will return to these clear-cut areas without being planted, based on an assumption that the seeds of native plants are dormant in the soil.  One wonders how these seeds would be able to germinate when covered with 24 inches of mulch, or how the sprouts could penetrate it.  Their proposal contains the fanciful suggestion that squirrels will plant the acorns of oaks in the mulch, which may be true of the oaks, but is an unlikely scenario for the many other native plants and trees which UC claims will populate their “restorations” without being planted.

Accommodating bees in native plant restorations

In the unlikely event that native plants would emerge from this tomb of mulch, they won’t find a population of bees to pollinate them in the future because bees will not be able to populate these projects:  “bees will not dig through a thick layer of mulch.”  Frankie suggests that “about 50% of your garden be left in bare dirt for the bees and other organisms.”  Studies indicate that it will take between 10 and 15 years for 24 inches of mulch to decompose.

Native plant restorations also require the use of herbicides.  A particularly toxic herbicide, Garlon, is used to kill the roots of the non-native trees after they have been cut down.  If the stump isn’t sprayed with this herbicide immediately, the tree will resprout.  The plans for the UC Berkeley projects say that retreatment with this herbicide is required twice per year for 10 years.  Although insecticides are considered one of the primary reasons why bee populations are declining in the United States, less is known about the effect of herbicides on bees and other insects, because testing of these chemicals is minimal. Some scientists believe that all pesticides (both insecticides and herbicides) are more harmful to bees and other animals than we presently know.*  Professor Frankie recommends against the use of all “synthetic chemicals” in a garden in which bees are welcome.

Would native plant restorations benefit from more bees?

The restorations with which we are familiar in the San Francisco Bay Area are often unsuccessful.  That is, they are not usually populated by native plants unless they have been intensively planted, weeded, and irrigated.  Few managers of public lands have the resources for such intensive gardening.  UC Berkeley has been clear-cutting non-native trees on its properties for about 10 years, so we can visit some of those areas to see the results of such projects.  They are now weedy messes, as shown in this photograph.

Results of clear-cutting non-native trees, UC Berkeley project

The use of heavy mulches and herbicides in native plant restorations raises these questions:    Would using less mulch and herbicide attract more bees?  Would more bees benefit the native plants?  Would restorations be more successful if they were more attractive places for bees?  We don’t claim to know the answers to these questions.  However, we don’t think that the managers of these projects know the answers either.

Would scientific methods produce more successful native plant restorations?

What the managers of these projects call “adaptive management,” we call “trial-and-error.”  There is no science involved in these projects.  Control areas are not set up to test questions such as “Will a more bee-friendly environment benefit our projects?”    We think a more methodical approach to these efforts would be less wasteful and more successful.  If we could see more success, perhaps we would be less opposed to what seems like the needless destruction of non-native trees.  As it is, the consistently poor results do not justify the destruction that we witness.

* Schacker, Michael, A Spring without Bees, Lyons Press, Guilford, Connecticut, 2008.

Nature is resilient, animals can adapt to change

We are always puzzled by the widespread belief amongst native plant advocates that native animals are dependent upon native plants and the corollary argument that non-native plants are invasive because they have no predators.  We suspect that one of many reasons for this assumption is a lack of understanding about evolution.  That is, if you believe that animals are unable to adapt to new plant species, then you probably assume that the new plant species are not useful nor are they prey to native animals.  

The Gallup Poll tracks the opinions of Americans regarding evolution.  In 2010 a surprisingly small percentage of Americans (16%) believed in the evolution of man unguided by God.  Even amongst those who believe in evolution, it is often seen as an historical process that moves too slowly to be perceived.  Science has only recently found living examples of on-going evolution:

“A growing appreciation that organic evolution, like mountain building, is an ongoing rather than simply historical process has stimulated an infusion of evolutionary thinking into mainstream ecology.”(1)

The Soapberry Bug

Soapberry bug on balloon vine. Scott Carroll, UC Davis

The soapberry bug (Jadera haematoloma) is an example of a native insect that has changed genetically in less than 100 generations over a period of 20 to 50 years in response to a new non-native plant host. 

The soapberry bug is named for the plant upon which it depends for both food and reproduction, the Sapindaceae family (‘Soapberry’ family).  In southern Florida, the native host plant of the soapberry bug was the balloon vine (Cardiospermum corindum).  As its name suggests, its seed is large and round.  The soapberry bug that feeds on that seed has a large jaw–up to about 70% of its body length–that enables it to get the seed into its mouth. 

In the 1950s a new member of the Sapindaceae family of plants was introduced to southern Florida, the Chinese flametree (Koelrueleria elegans) as an ornamental.  Its seed is much smaller than the seed of the balloon vine.  The soapberry bug quickly made a transition to its new host and over time it evolved several adaptations to it.  The jaw of the soapberry bug that feeds on the flametree is much smaller, as little as 50% of its body length. 

The life cycle of the soapberry bug has also changed and is better suited to the brief, simultaneous availability of seeds of its new host, the flametree:  “The flametree-specialized race [of soapberry bug] has a briefer development time (and thus an earlier age at first reproduction), greater fecundity, and exhibits greater expenditure of effort towards reproduction than the balloon vine race of J. haematoloma from which they originated.”(2)

In south Florida, the soapberry bug now has two genetically distinct races that are suited to their specific hosts–one native, one not.  The original race has not changed where its host is the native balloon vine.  The soapberry bug is not very mobile, so these two populations are physically separated.  This is an example of increased genetic biodiversity in response to an introduced plant. 

There are 400 genera and 1,500 species of plants in the Sapindaceae family all over the world(3), so we should not be surprised to find many other examples in the scientific literature of insect hosts that are adapted to them, whether they are native or introduced plants, as well as differences in those insects that are suited to the specific plants and/or their locations.  The soapberry bug isn’t an isolated example of an insect that has rapidly evolved to adapt to new hosts.  On the other hand, science cautions us against generalizing to all insects. 

We offer our readers three sources of information, depending upon their scientific knowledge.  The National Public Radio story about soapberry bug evolution is addressed to the layman.  At the opposite extreme, the citation in our footnotes is addressed to scientists with expertise in genetics.  The middle ground, from which we drew most heavily, is a website about soapberry bugs. 

Cheerful conclusion

As we often do, we conclude cheerfully that nature is remarkably resilient.  Although nature is less fragile than native plant advocates believe it to be, we don’t take that as an invitation to abuse it.  We treat nature with respect, and that includes taking care of what is here, whether it is native or non-native.  

(1) Carroll, Scott P., et. al., “Genetic architecture of adaptive differentiation in evolving host races of the soapberry bug, Jadera haematoloma,” Genetica, 112-113: 257-272, 2001

The Bees of Berkeley

Gordon Frankie is a Professor in the Department of Environmental Science, Policy and Management at UC Berkeley.  He has been studying the preferences of bees in northern California for over 20 years.  In 2002 he published an article in Fremontia, the journal of the California Native Plant Society, reporting on the preliminary results of his study.*

First, a word about the methods used in his study.  His research team visited the residential gardens of north Berkeley and Albany twice per week for three years, 1999 to 2002.  In the first stage of the study, the team identified the plants that were being visited by bees.  In the third year, they focused on counting the number of visits made to the identified “bee plants” by each species of bee.

The plants of Berkeley

Frankie’s team reports having identified 600-700 different varieties of non-native plants in the study area.  Native plants were defined as those that occur historically only in northern California.  Only 50 species of native plants were identified in the study area.

The bees of Berkeley

Frankie was surprised by the diversity of the bee population found by his research team.  They report having identified 74 different species of bees (updated on his website to 81).  Of those, only two were non-native bees (the European honeybee and the leaf cutting alfalfa bee).  Putting these numbers into perspective, there are approximately 1,600 species of bees in California and about 4,000 known to occur in the U.S.  Frankie reported that the population of European honeybees in the study area has declined significantly in the past 10 to 15 years.

What do the bees of Berkeley want?

The bees were observed visiting a small number of the total number of flowering plants available to them.  Only 72 species of flowering plants were visited by bees often enough to be counted by this study as “bee plants,” about 10% of the total number of flowering plants available to them.  Fifty-three of the “bee plants” were non-native and 19 were natives. 

Native bumblebee on non-native cotoneaster, Albany Bulb, Albany, California

While the bees of Berkeley are using a higher percentage of the available native plants (38%) than they are of non-native plants (8%), the percentage of non-native plants they are using is nearly 75% of all the flowers they are using.   Clearly, the non-native plants are important to the bees of Berkeley.

Frankie explains that many non-native plants are not useful to bees because they have been cultivated for looks, rather than for the nectar and pollen needed by the bees.  However, on his website, he updates his research with some strong recommendations to include both natives and non-natives in our gardens both for the benefit of the bees and the benefit of native plants.

Non-native plants extend the blooming period in our gardens, which provides food to the bees for a longer period of time:

“California native [plants] tend to flower in early spring and summer, while non-native ornamentals bloom mainly in late summer to fall, so a combination of both would be ideal for attracting the highest potential density of bees.”

Also, when our gardens attract more bees, all the plants in our gardens benefit from their pollination services, which will also benefit the native plants in our gardens:

“If your priority is a healthy garden, it makes good ecological sense to consider your plants’ bee-attractiveness, rather than focusing exclusively on whether one hundred percent of your plants are natives.  Even if your priority is to have a native garden, it can be highly advantageous to include even a couple of exotic plants on the basis of their bee-attractiveness.  The bees they attract will help your natives thrive.”

Frankie reminds us that the bees don’t care about the nativity of the plants that they use. 

“Insects and other wild animals make no distinction between weeds and plants we put in our gardens.  From the perspective of the bee, any plant that provides quality pollen and nectar is attractive.  For the short period they are in bloom, weeds such as dandelions and white clover provide bees with good sources of pollen and nectar.”

Opening our minds to the benefits of non-native plants

The bees of Berkeley remind us that the obsession with native plants is a human hang up that is not shared by animals.  They consider the nativity of the plants that are useful to them to be irrelevant.  So should we. 

* Gordon Frankie, et al, “Bees in Berkeley,” Fremontia, July/October 2002

Evolution didn’t stop in 1492

One of the most appealing of the many arguments used by native plant advocates in support of their ideology is the evolutionary concept of “co-evolution.”  Co-evolution is defined by Forgotten Pollinators(1) as “The idea in evolutionary ecology that certain mutualistic organisms have directed or redirected each other’s evolutionary trajectory.”  The implication of this theory is that plants and animals that have evolved together are interdependent and that loss of a particular plant will result in the loss of the animals with which it evolved.  Native plant advocates sometimes describe these relationships as “a lock and key,” implying that native plants and animals fit together in a mutually beneficial relationship which is exclusive. 

Those who believe this theory are obviously deeply committed to saving all native plants because they believe the loss of any single plant would inevitably lead to the loss of the animals that are dependent upon it.  Likewise, non-native animals are often exterminated based on the assumption that they compete with native animals and that loss of native animals will lead to the loss of native plants.

There are three problems with this theory. First, while there are some examples of truly exclusive co-evolved relationships in which both species cannot survive without the presence of the other, the number of such relationships is quite small.  Second, even these relationships are not immutable because evolution has not stopped, and therefore other species may develop mutualistic relationships with the prior exclusively mutualistic species.  And third, organisms are opportunistic and are quick to take advantage of any new opportunities, meaning that many interactions observed between species in the wild are not co-evolved at all.  For example, the honeybee pollinates hundreds of species of North American plants and it didn’t evolve with any of them (since honeybees were introduced into North America from Europe, which had introduced them from Africa).

Why is “co-evolution” rare in nature?

When defining “co-evolution” Forgotten Pollinators adds this caveat, “Good examples of truly reciprocal coevolution are difficult to find.”  Although the concept of “co-evolution” has a certain logical appeal, the explanation for why it is rare in nature is even more logical:  it is a risky survival strategy in a world that is constantly changing.  If, for example, the specific plant upon which a specific animal depends doesn’t bloom or doesn’t return from its dormant phase because of a sudden, even temporary, change in the climate, the animal that is dependent upon that plant is out of luck.  Since such fluctuations of environmental conditions are common, natural selection does not favor the animal that is restricted to a single plant for which there is no substitute.  Such exclusive relationships therefore do not persist in nature.

Nature provides “back-ups” that will enable plants and animals to respond to fluctuating environmental conditions.  For example, few plants have a single pollinator.  Most have several, usually of several different types.  One bee may be a particularly effective pollinator of a particular plant, but that plant is probably also visited by a fly, a butterfly, a bird, a beetle, etc.  As humans do, plants and animals don’t just give up when conditions change.  We all look for and usually find other alternatives. 

Native bumblebee gathering nectar and/or pollen from non-native cotoneaster. Albany Bulb, Albany, California

“Evolution right under our nose”

The Science Section of yesterday’s New York Times features an article about evolution of animals in New York City.   In the most densely populated city in the country, founded nearly 400 years ago, 74% of the native plant species that existed when the city was founded in 1624, still exist there.(2)  San Francisco has an even lower rate of extirpation of its native plants since it was founded in 1850.  Ninety-seven percent of the 714 plant species known to exist in San Francisco in 1850 are still found in San Francisco. 

Midtown Manhattan as seen from the Empire State Building. Creative Commons Attribution Share Alike

The fascinating article in the New York Times reports that the ability of animals to evolve in response to changing environmental conditions has enabled their survival in the urban environment. 

The white-footed mouse is an example of a native animal that is thriving in New York City.  The urban environment creates isolated urban islands, such as parks.  Scientists find that virtually every park in New York City has a population of genetically unique white-footed mice.  In fact, “The amount of [genetic] differences you see among populations of mice in the same borough is similar to what you’d see across the whole southeastern United States,” according to the scientist studying this mouse in New York City.

It’s difficult to imagine a more altered, artificial environment than the road medians on Broadway on the Upper West Side of Manhattan, which are composed of landfill used to cover the subway tunnel.  However, scientists have found 13 species of ants living in some of these medians.  Nine of the thirteen species are native. 

Nature is opportunistic and resilient.  It isn’t necessary to eradicate non-native plants and animals to ensure the survival of native plants and animals.  What greater laboratory to illustrate the resilience of nature than New York City? 

(1) Buchmann and Nabhan, The Forgotten Pollinators, Island Press, 1996

(2) Duncan et al, “Plant traits and extinction in urban areas:  a meta-analysis of 11 cities,” Global Ecology and Biogeography, July 2011