Why are we poisoning ourselves?

Americans banned DDT in 1972 and PCBs a few years later. We pat ourselves on the back for banning these and other toxic chemicals, but should we? Recent research suggests that though they were banned forty years ago, they are still making us sick.

Although these chemicals were banned, the chemical industry continues to churn out new products about which we know little. Will we find out decades later that these new chemicals are just as likely to poison us as their predecessors? The history of their predecessors suggests that is a likely outcome.

Living with the consequences of our folly

The National Research Council recently published a report (1) that informed us that at least 126,000 sites throughout the country have contaminated groundwater that requires remediation. About 10% of those sites are considered “complex” which is a euphemism for the fact that the technology required to clean them up does not presently exist, meaning that restoration is unlikely to be achieved in the next 50 to 100 years. The report estimates the cost of cleaning up these sites will be from $110 billion to $127 billion. However, the report also acknowledges that both the estimate of the number of sites and the cost of the clean up are probably underestimates.

What are the consequences of living with toxic chemicals? Researchers at Brown University tested the blood of over 3,000 women between the ages of 16-49 for levels of mercury, lead, and PCBs. These three chemicals are known to harm brain development of fetuses and babies. The sample was designed to represent the national population of 134.4 million women of childbearing age. Here’s what they found:

  • “Nearly 23 percent of American women of childbearing age met or exceeded the median blood levels for all three chemical pollutants.” (2)
  • “All but 17.3 percent of the women aged 16 to 49 were at or above the median blood level for one or more of these chemicals, which are passed to fetuses through the placenta and to babies through breast milk.” (2)
  • “As women grew older, their risk of exceeding the median blood level in two or more of these pollutants grew exponentially to the point where women aged 30 to 39 had 12 times greater risk and women aged 40-49 [born before these chemicals were banned] had a risk 30 times greater than those women aged 16 to 19.” (2)
  • “Fish and alcohol consumption also raised the risk of having higher blood levels. Women who ate fish more than once a week during the prior 30 days had 4.5 times the risk of exceeding the median in two or more of these pollutants.” (2)
The body burden of multiple pollutants
The body burden of multiple pollutants

While these findings are horrifying, they pale in comparison to the stunning finding that “One risk factor significantly reduced a woman’s risk of having elevated blood levels of the pollutants, but it was not good news: breastfeeding. Women who had breastfed at least one child for at least a month sometime in their lives had about half the risk of exceeding the media blood level for two or more pollutants. In other words, …women pass the pollutants that have accumulated in their bodies to their infants.” (2)

This particular study emphasizes the consequences of these pollutants for the children of the women who were tested. What about the women themselves? Surely these pollutants are also affecting their health and well-being. We turn to an outstanding book—Living Downstream– by an ecologist and cancer survivor (so far) for an answer to this question.(3)

First we must acknowledge how little we know about the connection between chemical pollution and its consequences to our health. The damage being done to our bodies by pollutants is not immediate nor is our exposure usually quantifiable which makes cause and effect very difficult to prove. Circumstantial evidence of the connection is therefore easily dismissed as anecdotal: women born in the United States between 1948 and 1958 had almost three times the rates of breast cancer in 1997 than their great-grandmothers did when they were the same age. Coincidentally, pesticide use in the United States had doubled between 1952 and 1997. (3, page 13)

Ironically, although DDT and PCBs were banned forty years ago, the connection between breast cancer and these pesticides was not discovered until after they were banned. The first study was conducted 4 years after DDT was banned on only 14 women with breast cancer. Significantly higher levels of DDT and PCBs were found in their tumors than in the surrounding healthy tissues. It took another 17 years to replicate that study on a statistically significant number of women: 14,200 women in New York City who had mammograms. The 58 women in that sample who were diagnosed with breast cancer had higher levels of DDT and PCB in their blood than women without breast cancer. (3)

It took nearly 50 years to prove that women with breast cancer have higher levels of DDT and PCB in their bodies than women without breast cancer. How long will it take us to learn what damage we are doing to ourselves with the pesticides that we are using now?

We aren’t testing for chemical pollution

Bacterial pollution at Pine Lake, San Francisco.  February 2012
Bacterial pollution at Pine Lake, San Francisco. February 2012. Courtesy Save Sutro

In San Francisco, the Department of Public Health tests the water bodies in the city for bacteria. In February 2012 they closed Pine Lake to the public because of bacterial levels. This incident prompted us to ask about San Francisco’s testing of water bodies. We learned that testing for bacteria is the ONLY test conducted in San Francisco. The watershed of Twin Peaks and Glen Canyon into Islais Creek was sprayed with pesticides over 30 times in 2011 by the Natural Areas Program, yet the water in the creek was not tested for pesticide levels. Islais Creek flows into the bay.

The need for more testing of water bodies was recently recognized by the European Science Foundation. (4) They conducted a poll of 10,000 citizens from 10 European countries which found that pollution is the top concern of the public among all concerns regarding the marine environment.

The public has good reason for their concern. There are presently about 30,000 chemicals available on the European market with production volume exceeding one ton per year. The volume of these chemicals entering rivers, streams, estuaries, and seas is increasing and potentially damaging marine organisms, ecosystems, and processes. Yet the testing of waters for these chemicals lags far behind the increasing number of chemicals being introduced to the environment.

We are on a pesticide treadmill

The tests required to put new chemicals on the market are minimal. The testing of pollution levels in the environment is also minimal. Yet, we continually introduce new pesticides about which we know little. Why? We speculate about the motivation for introducing new pesticides into the environment:

  • As the patents on pesticides expire, the manufacturers must introduce new pesticides in order to maintain their profit margins.
  • The longer a pesticide is in use, the more likely its target is to build up a resistance to it. Hundreds of weeds are resistant to available herbicides. Hundreds of insects are resistant to available insecticides.
  • The less the public knows about a pesticide, the less likely they are to be afraid of it and the less likely they are to object to its use..

Why is this issue relevant to Million Trees?

Our regular readers might wonder what this has to do with the mission of Million Trees to inform the public of the destruction of non-native trees for the purpose of creating native plant gardens. The connection is that the use of pesticides by these projects is skyrocketing as the war on non-native plants escalates.

Volume of pesticide use by San Francisco's "Natural Areas Program."  Courtesy San Francisco Forest Alliance
Volume of pesticide use by San Francisco’s “Natural Areas Program.” Courtesy San Francisco Forest Alliance

Those who work for these projects and those who support them defend their use of pesticides in our public parks by telling us they are following the rules, and the rules guarantee no harm will be done by the pesticides. What they don’t seem to understand is that many of the pesticides—and other chemicals—that we now know are harmful to us and the animals that we live with, were legal when they were used. They were legal because we did not know yet that they were harmful.

It took decades for us to understand that the pesticides we were using were harmful. We see no reason to believe that the pesticides we are using now will not also prove to be harmful. By the time we learned how harmful they are, a great deal of damage had already been done. And although many were banned decades ago, they persist in the environment and in our bodies. Therefore, we object to the frivolous use of pesticides in our public parks. Using pesticides for the purpose of killing vegetation solely because it is non-native is irresponsible, given the potential damage they can do to humans and wildlife.


(1) National Academy of Sciences, “Clean-up of some U.S. contaminated groundwater sites unlikely for decades,” November 8, 2012

(2) Marcella Remer Thompson, Kim Boekelheide, “Multiple environmental chemical exposures to lead, mercury, and polychlorinated biphenyls among child-bearing-aged women: Body burden and risk factors,” Elsevier, November 16, 2012

(3) Sandra Steingraber, Living Downstream, Addison-Wesley, 1997

(4) European Science Foundation, “Chemical pollution in Europe’s Seas: The monitoring must catch up with the science,” March 21, 2012

Low doses of pesticides are also hazardous to our health

We are reprinting, with permission, an article on the Save Sutro website about recent research reporting that even low doses of chemicals can be harmful to our health.  This research has serious implications for the pesticides being used by the many “restoration” projects in the San Francisco Bay Area.  This article is focused on pesticide use by San Francisco’s misnamed Natural Areas Program.  In fact, every manager of public land in the Bay Area that engages in native plant “restorations” uses pesticides to eradicate non-native species. 


When we speak up against the Natural Area Program’s frequent pesticide use, its supporters frequently tell us that – compared with say commercial agriculture – the Natural Areas Program (NAP) uses small amounts of toxic chemicals. “The dose makes the poison,” they argue.

But it’s not true.

For now, we’ll leave aside the question of whether it’s reasonable to compare NAP to  commercial agriculture (where fears of chemicals are driving a growing Organic movement). What we’d like to talk about today is recent research about pesticides, specifically, endocrine disruptors. Here’s a quote from the abstract of a study by a group of scientists:

“For decades, studies of endocrine-disrupting chemicals (EDCs) have challenged traditional concepts in toxicology, in particular the dogma of “the dose makes the poison,” because EDCs can have effects at low doses that are not predicted by effects at higher doses….

“…Whether low doses of EDCs influence certain human disorders is no longer conjecture, because epidemiological studies show that environmental exposures to EDCs are associated with human diseases and disabilities. We conclude that when nonmonotonic dose-response curves occur, the effects of low doses cannot be predicted by the effects observed at high doses.”

[Ref: Hormones and Endocrine-Disrupting Chemicals: Low-Dose Effects and Nonmonotonic Dose Responses, Vandeberg et al, in Endocrine Reviews, March 2012]


The NAP uses several pesticides rated as “Hazardous” or “Most Hazardous” by San Francisco’s Department of the Environment. But the one they’ve favored is glyphosate — better known as Roundup or Aquamaster.

It’s strongly suspected of being an endocrine disruptor.

Here’s a 2009 study: Glyphosate-based herbicides are toxic and endocrine disruptors in human cell lines.

Another study, also published in 2009, looked at puberty and testosterone: Prepubertal exposure to commercial formulation of the herbicide glyphosate alters testosterone levels and testicular morphology. The abstract of the study ends with this sentence, “These results suggest that commercial formulation of glyphosate is a potent endocrine disruptor in vivo, causing disturbances in the reproductive development of rats when the exposure was performed during the puberty period.”

And here’s a study published in 2007, reflecting the research of a group of scientists from Texas A&M: Alteration of estrogen-regulated gene expression in human cells induced by the agricultural and horticultural herbicide glyphosate


Most people weren’t aware that pesticides were being used in so-called “Natural Areas.” The notices were small and well below eye-level. You had to be looking for them, which isn’t likely for most people out hiking or jogging by, or keeping an eye on small kids. In recent months, the labeling has improved, with taller posts and clearer information.

Now that people are beginning to notice, they’re also objecting. The response we hear most often is “Why would they use herbicides in a natural area?”

So the NAP has started posting explanations, justifying its use of toxic herbicides justifiable against “invasive plants.”

These plants, they say, are “a handful of non-native species” that are “displacing the rich biodiversity of native flora and degrading our natural heritage.”


We have several problems with this statement.

  • If it’s a “handful,” the NAP must have very big hands. From the pesticide application records, we’ve counted nearly twenty-five different plant species under attack by chemicals — including a couple that aren’t actually non-native.
  • There’s no evidence that all these plants are invasive and that they’re “displacing the rich biodiversity.” Native plants and non-native plants thrive together in natural mixed ecosystems. NAP can never eliminate all the non-native plants; the best it can achieve is a different mix, precariously maintained through intensive gardening.
  • There’s also no evidence it’s working. Using chemicals to kills things is cheap and easy, but it leaves a gap where something else will grow. Given that San Francisco’s environment has changed greatly since the 1776 cut-off used to define “native” plants, it’s not going to be those plants. Rather, what will naturally grow back will be the most invasive plant at the site. An excuse for more herbicides.
  • The NAP is destroying habitat in its quest to kill native plants. Many of the plants destroyed are bushes that provide cover and nesting places, or flowering plants that offer nectar to butterflies, bees and other pollinators and the birds and animals that feed on them. The “native flora” don’t necessarily provide much of either, even if they can be successfully gardened.

Escalating pesticide use by the unnatural Natural Areas Program

Webmaster: We are grateful to Save Mount Sutro Forest for their research on pesticide use by San Francisco’s misnamed Natural Areas Program and for giving us permission to reprint this update on NAP’s pesticide use in 2011.


We spent a couple of hours, the other day, in the beautiful McLaren Lodge, leafing through a thick binder of pesticide reports for the San Francisco Rec and Park Department. It was so thick in part because it contained a lot of nil reports… supervisors of various sections writing in to say things like “No Roundup used in this complex.

The monthly reports from the Natural Areas weren’t nil. Far from it.

Some months ago, we wrote that the pesticide use in the Natural Areas seemed to have increased sharply in 2010 compared with 2009. Oh, said a critic, don’t focus on an individual year. It might go back down next year, it might just be a blip.

If so, we’re not blip-free yet. According to our preliminary figures (which we will update if we get better information) pesticide applications in 2011 were up 20% from 2010.

The NAP continues to use glyphosate regularly (38 39 times in 2011). It’s mostly switched from Roundup to a different formulation, Aquamaster. This alternative provides better control over the adjuvant, the stuff that the pesticide is mixed with. It still contains glyphosate, with its attendant risks.


Part of the reason for switching to Aquamaster is that POEA, the adjuvant in Roundup, is actually toxic instead of being inert. But it’s not just the POEA. Glyphosate itself has problems, particularly in terms of pregnancy problems and birth defects. A 2005 article published in the journal of the National Institutes of Health noted that glyphosate was toxic to placental cells (and Roundup was even more so):

“… glyphosate is toxic to human placental JEG3 cells within 18 hr with concentrations lower than those found with agricultural use, and this effect increases with concentration and time or in the presence of Roundup adjuvants.”

In addition, it’s an endocrine disruptor. French scientists published an article in the journal Toxicology titled, “Glyphosate-based herbicides are toxic and endocrine disruptors in human cell lines.”

According the the guidelines from San Francisco’s Department of the Environment, Aquamaster is to be used “Only as a last resort when other management practices are ineffective.” Since this last resort occurs some 40 times in a year, we suggest the DoE consider reclassifying Aquamaster as Tier I to reflect the latest research on glyphosate.


The big change this year was the move from Garlon (triclopyr) to Polaris or Habitat (imazapyr). According to the record, Garlon was only used thrice in 2011, while imazapyr was used 40 times.

This is somewhat of an improvement in that Garlon is a very toxic chemical, classified as Tier I; imazapyr is less toxic and classified as Tier II.

Unfortunately, it’s possible that the best thing about imazapyr is that it isn’t as bad as Garlon. It is very persistent, and doesn’t degrade easily. It moves around, being exuded by the roots of the plants it’s meant to poison. And its break-down product is a neurotoxin – it poisons the nervous system. It’s banned in the European Union.

The NAP also used Milestone four times. (That does sound like a last resort.) Fortunately. Milestone is an extraordinarily persistent chemical that has been withdrawn from sale in the UK, and is rightly classified as Tier I, Most Hazardous.


The NAP also continued to violate pesticide guidelines. In August 2011, they used Aquamaster against ludwigia (water primrose) in Lake Merced — a lake that is considered red-legged frog habitat. The guidelines ask for a 60-foot buffer zone. Since the water primrose is in the water (and so, we presume is the frog), this buffer zone’s not happening.

Some readers will remember this post about the dateless sign threatening pretty much all the vegetation near the Twin Peaks reservoir with Garlon and Aquamaster. We never got to the bottom of that. The pesticide records don’t mention it.

[Edited to Add (22 Jan 2012): One of our readers asked about this Glen Canyon notice, too, listing the use of Glyphosate and Imazapyr against ivy and acacia.

Again, we don’t know what happened but it’s not in the pesticide records.]


Shelterbelt Builders, the contractor the Natural Areas uses for pesticide application, earned more fees from Rec & Park as pesticide applications increased:

  • In fiscal 2009-10 (year ending June 30), it earned $51 thousand;
  • In fiscal 2010-11, it was paid $78 thousand;
  • In fiscal 2011-12, it’s been paid (or is owed) a total of $84 thousand, and the fiscal year is only half-finished.

[Edited to Add: This is public information from the SF Controller’s website. You can see it here. ETA2: The report on the SF Controller’s website has been changed. Here is the new link. Also, the picture here can be enlarged by clicking on it until it’s readable.]

On Mount Sutro, though the Sutro Stewards’ volunteers have been gutting the understory and destroying habitat, we are glad to say there is still no use of herbicides. Again, our thanks to UCSF for preserving possibly the last pesticide-free wildland in San Francisco. Even if only temporarily.


It’s not a good time to be a plant or a tree in San Francisco. The San Francisco Chronicle reports that the city is handing off 23,000 street trees to homeowners to care for. It estimates it will save $300 thousand. The kind of comments people made on the article don’t bode well for the future of those trees. Meanwhile, it seems to be able to find funding to destroy trees in Natural areas across the city, trash habitat needed by the city’s wildlife, and take out quirky old trees that give some of these wild areas their character.

Response to Nature in the City

Nature in the City (NIC) is one of many organizations that support native plant “restorations” in San Francisco as well as the principle entity which engages in them, the Natural Areas Program (NAP) of the Recreation and Park Department.  NIC is consistently critical of anyone who questions the value of these restorations, but in their most recent newsletter they confront our objections directly.  Although we don’t presume to represent the many constituencies which are critical of the Natural Areas Program, we are responding in this post to NIC based on our knowledge of the issues. (The NIC newsletter is in quotes and is italicized.  Our response is not italicized.)

“Natural Areas in 2012

Last fall saw the the [sic] Planning Commission public meeting for the Draft Environmental Impact Report (DEIR) for the Significant Natural Resource Areas Management Plan.  Some time later this year, the City will issue a Final Environmental Impact Report, which may be appealed by opponents of the Natural Areas Program.

Unfortunately, a handful of people are still propagating misinformation about the rationale, values, and intention of ecological restoration, management and stewardship, and of the City’s celebrated Natural Areas Program.”

Webmaster:  Critics of the Natural Areas Program cannot be described accurately as a “handful of people.”  We now have four websites(1) representing our views and there have been tens of thousands of visits to our websites.  Comments on our websites are overwhelmingly supportive of our views. Our most recently created website, San Francisco Forest Alliance, lists 12 founding members.  That organization alone exceeds a “handful of people.”

Our objections to the Natural Areas Program have also been reported by three major newspapers in the past month or so (San Francisco Examiner, Wall Street Journal,  Sacramento Bee).

 Many critics of NAP have been engaged in the effort to reduce its destructive and restrictive impacts on our parks for over 10 years.  Scores of public meetings and hearings have been held to consider our complaints.  We consistently outnumbered public speakers in support of NAP until 2006, when the NAP management plan was finally approved by the Recreation and Park Commission.  Although we were outnumbered for the first time, there were over 80 speakers who asked the Recreation and Park Commission to revise NAP’s management plan to reduce its negative impact on our parks.

The public comments on the NAP DEIR are the most recent indicator of the relative size of the groups on opposite sides of this issue.  These comments were submitted in September and October 2011.  We obtained them with a public records request.  The Planning Department reported receiving about 400 comments.  In analyzing these comments, we chose to disregard about half of them because they were submitted as form letters, even though they were from dog owners who were protesting the loss of their off-leash privileges in the natural areas.  We also leave aside the comments from golfers whose only interest is in retaining the golf course at Sharp Park.  In other words, we set aside the majority of the comments critical of the NAP management plan in order to focus on those comments that demonstrate a comprehensive understanding of the impact of NAP on the city’s parks.  Of the comments remaining, those critical of NAP and its deeply flawed DEIR outnumbered comments in support of the NAP DEIR about three to one.  We urge NAP supporters to read these public comments to learn about the wide range of criticisms of NAP, including pesticide use, destruction of trees, recreational access restrictions, loss of wildlife habitat and more. 

We will challenge NIC’s accusation that we are “propagating misinformation” within the context of their specific allegations:

“Contrary to the many myths that continue to percolate, the Natural Areas Plan and Program seek to do the following (among other worthwhile endeavors):

1.       Protect and conserve our City’s natural heritage for its native wildlife and indigenous plant habitats and for the overall health of our local ecosystem;”

Webmaster:  Since the majority of acreage claimed as natural areas by NAP 15 years ago had no native plants in them, there is little truth to the claim that NAP is protecting our “natural heritage.”  The so-called “natural area” at Balboa and the Great Highway is typical of the “natural areas.”  There is photographic evidence that it was built upon for about 150 years.  It was the site of Playland by the Beach before it was designated a “natural area.”  Sand had to be trucked onto the property and disked down 18” into the construction rubble, then shaped into dunes by bulldozers before native plants could be planted on it. 

Natural Area at Balboa & Great Highway under construction

We don’t make any distinction between “native wildlife” and any other wildlife currently living in our city.  We value them all.  Most are making use of existing vegetation, whether it is native or non-native.  They do not benefit from the loss of the blackberries that are their primary food source or the loss of the thickets or trees that are their homes.  We do not believe that wildlife in San Francisco benefits from the destructive projects of the Natural Areas Program.  See photos of insects, birds, and other wildlife using non-native plants in the natural areas here.

Damselflies mating on ivy, Glen Canyon Park

We do not think an ecosystem that has been sprayed with herbicides qualifies as a “healthy ecosystem.”  NAP sprayed herbicides at least 86 times in 2011.  Their use of herbicides has increased over 330% in the last 4 years.  NAP uses herbicides that are classified as more toxic than those most used by other city departments.  Last spring, 1,000 visitors to Glen Canyon Park signed a petition, asking the Natural Areas Program to stop using pesticides in their park.  This petition was given to Scott Wiener, the Supervisor representing the district in which Glen Canyon Park is located.

These are statements of fact that can be easily verified by the public record.

2.       “Educate our culturally diverse city about the benefits of local nature and about helping with natural areas stewardship in your neighborhood;”

Webmaster:  Although we value education, we do not consider the staff of NAP and/or its supporters qualified to provide it.  We hear them make statements that are demonstrably not true, such as “grassland stores more carbon than trees.”  We see them spray herbicides in the dead of winter that are supposed to be sprayed in the spring when the plants are actively growing.  We watch them plant things where they won’t grow, such as sun-loving plants in deep shade and plants in watersheds where they will soon be drowned by seasonal rains.

And we also have had bad experiences with the volunteers who are called “stewards” by NAP, but sometimes act more like vandals.  We see them spraying herbicides that they aren’t authorized to use.  We see them hacking away at trees that haven’t been designated for removal.  NAP is not providing the necessary guidance and supervision to the volunteers many of whom seem to consider themselves the de facto owners of the parks. 

3.       “Manage the City’s wildlands for public access, safety and the health of the “urban forest.””

Webmaster:  We do not oppose the removal of hazardous trees.  However, we also know that most of the trees that have been designated for removal by the NAP management plan are NOT hazardous.  They have been selected for removal solely because they are not native and are perceived to be obstacles to the reintroduction of native plants.  Claims to the contrary are inconsistent with the management plan as well as our experience in the past 15 years.  (Watch video about the destruction of 1,600 trees over 15 feet tall planned for Mt. Davidson.)

“We hear occasional complaints about public access and tree removal. Three simple facts are thus:

1. Every single natural area in the City has at least one trail through it, where one can walk a dog on a leash;”

Webmaster:  The loss of recreational access in the natural areas is real, not imagined.  The following are verbatim quotes from the NAP management plan:

  • “Approximately 80 percent of the SFRPD off-leash acreage is located within Natural Areas.” (page 5-8).  The NAP DEIR proposes to close or reduce the size of several off-leash areas.  The DEIR provides no evidence that these areas have been negatively impacted by dogs.  It also states that all off-leash areas in the natural areas are subject to closure in the future if it is considered necessary to protect native plants.  Since NAP has offered no evidence that the proposed immediate closures are necessary, one reasonably assumes it will offer no evidence if it chooses to close the remainder of the 80% of all off-leash areas in San Francisco located in natural areas.  We know from the DEIR public comments that NAP supporters demand their closure.
  • Public use in all Natural Areas, unless otherwise specified, should encourage on-trail use… Additionally, interpretive and park signs should be installed or modified as appropriate to include “Please Stay on Trails” with information about why on-trail use is required.”  (page 5-14)   In other words, the only form of recreation allowed in the natural areas is walking on a trail.  Throwing a ball or frisbee, having a picnic on the grass, flying a kite, climbing the rocks are all prohibited activities in the natural areas.  And in some parks, bicycles have been prohibited on the trails by NAP. 
  • “Finally, this plan recommends re-routing or closing 10.3 miles of trail (approximately 26 percent of total existing trails).” (page 5-14)  So, the only thing visitors are allowed to do in a natural area is walk on the trails and 26% of all the trails in the natural areas will be closed to the public.

2. “The act of removing (a small subset of) non-native trees, e.g., eucalyptus, that are in natural areas has the following benefits:
   a. Restores native habitat for indigenous plants and wildlife;
   b. Restores health, light and space to the “urban forest,” since the trees are all crowded together and being choked by ivy;
   c. Contributes to the prevention of catastrophic fire in our communities.”

Webmaster:  Destroying non-native plants and trees does not restore indigenous plants and wildlife. Native plants do not magically emerge when non-native plants and trees are destroyed. Planting indigenous plants might restore them to a location if they are intensively gardened to sustain them.  However, in the past 15 years we have seen little evidence that NAP is able to create and sustain successful native plant gardens.  Native plants have been repeatedly planted and they have repeatedly failed. 

NAP has not “restored” the health of the urban forest.  They remove trees in big groups as they expand their native plant gardens.  They are not thinning trees.  They are creating large openings for the grassland and dune scrub that they plant in the place of the urban forest.  Every tree designated for removal by the NAP management plan is clearly selected for its proximity to native plants.  It is disingenuous to suggest that NAP’s tree removal plans are intended to benefit the urban forest.

Of all the fictions fabricated by native plant advocates to justify the destruction of our urban forest, the claim that its destruction will “prevent catastrophic fire” is the most ridiculous.  The native ecology of California is highly flammable.  Most fires in California are in native chaparral.  According to San Francisco’s hazard mitigation plan, there has never been a wildfire in San Francisco (2) and one is unlikely in the future because the climate is mild and moist.  When it is hot in the interior, it is foggy in San Francisco.  The hot winds that drive most fires in California never reach San Francisco because it is separated from the hot interior by the bay.  San Francisco is surrounded by water, which moderates its climate and virtually eliminates the chances of wildfire. The tall non-native trees precipitate moisture from the summer fog, which moistens the forest floor and reduces the chances of ignition.  In the unlikely event of a wind-driven fire, the trees provide the windbreak which would stop the advance of the fire. 

3. “The overall visual landscape of the natural areas will not change since only a small subset of trees are planned to be removed over a 20-year period.”

Webmaster:  In addition to the 18,500 trees over 15 feet tall which NAP proposes to destroy, the NAP management plan also states its intention to destroy non-native trees less than 15 feet tall.  In other words, the future of the forest will also be killed.  The intention is to eliminate the urban forest in San Francisco’s parks over the long term.  Yes, this will take some time, but the long-term intention to eliminate the forest is clear.

“Please feel free to email steward@natureinthecity.org if you would like more clarification about the intention, values and rationale of natural resources management.”

Webmaster:  We urge our readers to take NIC up on this offer to provide  ”more clarification” of its spirited defense of the Natural Areas Program. 

  • Do you think NIC is deluded about there being only a “handful of people” that are critical of the Natural Areas Program?
  • Did you notice that NIC does not acknowledge the use of herbicides by NAP?  Do you think that a fair representation of criticism of NAP can omit this issue?
  • If you visit a park that is a natural area, do you think NAP has demonstrated in the past 15 years what NIC claims it is accomplishing?
  • Do you think NIC has accurately described recreational access restrictions in the natural areas?
  • Do you think that San Francisco’s urban forest will be improved by the destruction of 18,500 mature trees and countless young trees?

(1) Save Sutro Forest, Urban Wildness, San Francisco Forest Alliance, Death of a Million Trees

(2) “The California Department of Forestry and Fire Protection (CAL FIRE) has no record of any wildfire in San Francisco.” San Francisco Hazard Mitigation Plan, 2008, page 5-18.

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