Ecology – Page 34 – Conservation Sense and Nonsense

Plans to destroy over 30,000 trees on Mount Sutro

We are reprinting with permission Save Sutro’s announcement of the Draft Environmental Impact Report for the project to destroy over 30,000 trees on Mount Sutro in San Francisco.

Here are the things you can do to participate in the effort to save this beautiful forest:

Sign the petition to save the forest. Available here.
Attend and speak at a UCSF hearing about the project: Monday, February 25, 2013, 7 pm, Millberry Union Conference Center, 500 Parnassus Ave, Golden Gate Room
Submit a written public comment by 5 PM, March 19, 2013 to UCSF Environmental Coordinator Diane Wong at EIR@planning.ucsf.edu or mail to UCSF Campus Planning, Box 0286, San Francisco, CA 94143-0286. Include your full name and address.
Write to the Board of Regents to ask why a public medical institution is engaging in such a controversial, expensive, and environmentally destructive act. Address: Office of the Secretary and Chief of Staff to the Regents, 1111 Franklin St., 12th Floor, Oakland, CA 94607  Fax: (510) 987-9224
Subscribe to the website SaveSutro.com for ongoing information and analysis.

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Mount Sutro Forest has approximately 45,000 trees in the 61 acres belonging to UCSF, and designated as an open space reserve. This dense forest, with an estimated 740 trees per acre, a sub-canopy of acacia, an understory of blackberry and nearly a hundred other plant species, is functionally a cloud forest. All summer long, it gets its moisture from the fog, and the dense greenery holds it in. Where it isn’t disturbed, it’s a lush beautiful forest, providing habitat for birds and animals, and a wonderful sense of seclusion from urban sounds and sights.

THE TREE REMOVAL PLAN

UCSF now has published a Draft Environmental Impact Report (DEIR) on a project to remove over 90% of the trees on three-quarters of the area. Only 15 acres – on the steep western edge of the forest – will remain as they are. Tree-felling could start as early as Fall 2013.

[Edited to Add:

Here is the PDF of the DEIR. Mount_Sutro_EIR_1-16-13_with_Appendices

Comments were due on March 4th, but because of the length and complexity of the document, neighbors asked for, and got, an extension. Comments are now due before March 19, 2013.]

On most of the forest (44 acres), UCSF plans to cut down trees to achieve a spacing of 30 feet between trees – the width of a small road – and mow down nearly all the understory habitat. On another 2 acres, they will space the trees 60 feet apart.

The stumps of the trees will be covered in black plastic, or else poisoned with Garlon to prevent re-sprouting. Eventually, this will kill the roots, which will start to decay. We’ll address some of these issues in more detail in later posts.

Right now, we want to talk about the number of trees that will be felled. A spacing of 30 feet between trees gives about 50-60 trees per acre. A spacing of 60 feet gives 12-15 trees per acre.

(The easiest way to think about it is that each tree occupies a 30 x 30 foot space, or 900 sq ft. An acre is 43,560 sq ft, so this would give 48.4 trees to an acre. The DEIR calculates it as 61 trees per acre, assuming each tree occupies a circle that’s 30 feet in diameter, 707 sq ft. But there’s no way to arrange circles without wasted spaces between them, so this doesn’t exactly work.)

So on 44 acres, they will retain maybe 50 trees per acre (or maybe fewer). On two more acres with a 60-ft spacing, they will retain 12-15 trees per acre. All the rest will be cut down. Even using the DEIR’s overly optimistic calculation, they will be felling some 31,000 trees. Our calculations are closer to 32,000. Either way, it’s a huge number.

That means that in the 46 acres where UCSF will be felling trees, they will remove more than 90% of the standing trees.

The DEIR says that they will start by cutting down trees that are dead or dying. Aside from their value as habitat (some birds like woodpeckers depend on them), there are not all that many of them in Sutro Forest, which despite everything that has been claimed to the opposite, is a thriving forest. Next in line will be trees with diameters under 12 inches, or roughly 3 feet around – as thick as an adult’s waist. Then they’ll start on the larger trees. Since it’s going to be 90% of the trees, we expect thousands of large trees to be removed.

IT GETS WORSE

However, this is not all. We expect further tree losses for four reasons:

Wind throw. Since these trees have grown up in a dense forest where they shelter each other, removing 90% of the trees exposes the remaining 10% to winds to which they’re not adapted. This can be expected to knock down a significant number of the trees not felled. Since the Plan only calls for monitoring the trees and felling any that seem vulnerable to wind-throw, it’s unlikely any vulnerable trees will be saved.
Physical damage. Damage done to the remaining trees in the process of removing the ones they intend to fell. With such large-scale felling, damage to the other trees is inevitable, from machinery, erosion, and falling timbers.
Pesticide damage. This forest has an intertwined, intergrafted root system. When pesticides are used to prevent resprouting on tree-stumps and cut shrubs and ivy, it is quite possible for it to enter the root system and damage remaining trees.
Loss of support. Compounding the effects of the wind-throw, the remaining trees will suffer from a lack of support as the root network dies with 90% of the trees being removed. This could destabilize them, and make them more likely to fail.

What remains will be a seriously weakened forest with a greater risk of failure and tree-loss, not the healthier forest that the DEIR claims. It is likely that the long-term impact of the Project will be the elimination of the forest altogether, and instead will be something like Tank Hill or Twin Peaks plus a few trees.

IMPLEMENTING THIS PLAN

The project is to be implemented in two phases. In the first phase, trees will be felled and the understory removed in four “demonstration areas” totaling 7.5 acres. They are shown on the map below in yellow, as areas #1-#4. (One of these, #4 “East Bowl”, is the two-acre area slated to have only 12-15 trees per acre.

One area (#5 on the map) is supposed to be a “hands off” area to demonstrate the untouched forest. However, a trail has already been punched through it in November 2011, even before the DEIR had been published.

During this phase, they would experiment with the 3 acres on the South Ridge, just above the Forest Knolls neighborhood. On 1 acre, they would use tarping to prevent regrowth of felled trees; on 1 acre, they would use pesticides, particularly Garlon; and 1 acre they would trim off sprouts by hand. They could also use pesticides on the understory “consistent with city standards” – presumably those of the Natural Areas Program (See article on NAP’s Pesticide Use.)

In the second year, the plan would be extended to the remaining forest, with the proviso that not more than a quarter of the forest would be “thinned” at “any given time

Why are native plant installations often failures?

We have been watching attempts to eradicate non-native plants and replace them with native plants on public lands in the San Francisco Bay Area for over 15 years. Few of these efforts have been successful. Non-native plants are repeatedly eradicated, then natives are planted. Within months the natives are dead and non-natives have returned.

The few projects that are successful are usually fenced, irrigated, and intensively planted and weeded. Few managers of public lands have the resources to achieve success. We have identified here on the Million Trees blog many reasons why attempts to return native plants to places in the Bay Area where they have not existed for over 100 years are often failures. Many of those reasons are related to the changes in the environment:

Higher levels of CO2 and associated climate change are promoting the growth of non-native plants. A USDA weed ecologist (1) studied the effects of higher temperatures and CO2 on the growth of non-natives (AKA weeds) by growing identical sets of seeds in a rural setting and an urban setting with higher temperatures and CO2 levels. Seeds grown in the urban setting produced substantially larger plants with much more pollen and therefore greater reproductive capability.
The growth of non-native annual grasses is encouraged by higher levels of nitrogen in the soil found in urban environments as a result of the burning of fossil fuels. (2)

The methods used by the projects undermine success

With the exception of the project on Mount Sutro in San Francisco, all of the projects use herbicides to eradicate the non-native plants and trees. Most of the non-native trees will resprout if their stumps are not sprayed immediately with herbicide and this must be done repeatedly to kill the roots of the trees. Many of these herbicides persist in the ground for years and probably suppress subsequent plant growth.

This problem is illustrated by a USDA study of the effects of a one-time aerial spraying of herbicides on grassland after 16 years. Although the herbicide is assumed to “dissipate” within a few years, the negative effect on the natives persisted 16 years later: “…the invasive leafy spurge may have ultimately increased due to spraying. Conversely, several desirable native herbs were still suffering the effects of the spraying,,,”

Anyone who is familiar with native plant restorations in the Bay Area knows that most are covered in a thick layer of mulch. When tree removals are required for a project, 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.

Chips of destroyed trees, UC Berkeley project. Photo courtesy Hills Conservation Network

These heavy mulches prevent native bees from nesting in the ground, as most native bees do. This reduces the population of pollinators which are essential to the germination of a new generation of the plants. If long-term sustainability is the goal of these projects, an environment that is friendlier to pollinators would be helpful.

Lack of horticultural knowledge is also handicapping these projects

One of 5 native oaks that survive on Tank Hill 10 years after 25 oaks were planted.

The managers of these projects often display a profound ignorance of basic horticultural knowledge. For example, we have seen them plant natives that require full sun in the deep shade of trees where they will not survive. We have seen them plant native trees that will not tolerate wind on the slopes of windy hills, only to watch the trees wither and die.

The managers of these projects are apparently unaware of the fact that hundreds of species of California native plants require fire to germinate their seeds and that most of the population will die within 5 years of the fire. (3) These are examples of such “pyroendemics” that sprout after a fire and are almost entirely gone within 5 years:

UC Berkeley and East Bay Regional Park District do not plan to plant any natives after eradicating non-native plants and trees. Their plans say that they expect seeds that are dormant in the ground to sprout when the ground is cleared of non-native plants. Unless they set fire to that ground, many seeds will not germinate and most of the plants that are germinated by that fire will disappear within 5 years unless another fire germinates another generation of plants.

UC Berkeley does not use prescribed burns on its property. East Bay Regional Park District (EBRPD) conducts only a handful of small prescribed burns every year, which they claim are solely for the purpose of reducing fuel loads. In an article about prescribed burns conducted by EBRPD, the District’s “Resource Analyst” is quoted as saying, “’This is not a restoration project. Our primary goal is fuels reduction.’” (4) Ironically, both of these owners of public lands claim that their objective in the eradication of non-native plants is to reduce fire hazard, yet they are trying to reintroduce a landscape that is dependent upon fire for survival.

The Natural Areas Program in San Francisco has never conducted a prescribed burn and the DRAFT Environmental Impact Report for their plan says they do not intend to do so in the future.

New and growing evidence that soil is altered by plants

In addition to these issues which have contributed to the failed attempts to reintroduce an historical landscape to the San Francisco Bay Area, we are reporting today on a new issue. Plants can change the microbial composition of the soil, including mycorrhizal fungi which have symbiotic relationships with plants.

Researchers tested soil for changes in composition after just three growth cycles. Several species of non-native annual grasses were grown in native soils. They reported that the non-native species reduced the population and changed the composition of the mycorrhizal fungi, which reduced the ability of native species to establish and persist in modified soils. (5)

The Berkeley Meadow is a 72-acre native plant garden on a former garbage dump on landfill.

These changes in the soil were observed after only three growth cycles. Our local projects are attempting to eradicate plants which occupied the soil for more than 100 years. In some cases such as the former garbage dumps in the East Bay on landfill, the soil was never occupied by native plants. Surely, the alteration of soil composition is a likely factor in the failure of attempts to turn these properties into native plant gardens.

How many more decades and how much more taxpayers’ money must we spend on these projects before land managers acknowledge their failures?

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(1) Lewis Ziska, USDA Scientist, Beltsville, MD

(2) US Fish & Wildlife, Recovery Plan for Mission Blue butterfly

(3) Jon Keeley, et. al., Fire in Mediterranean Ecosystems, Cambridge University Press, 2012

(4) Wendy Tokuda, “Taming the Flames,” Bay Nature, July-September 2012

(5) Nicholas Jordan, et. al., “Soil-Occupancy Effects of Invasive and Native Grassland Plant Species Composition and Diversity of Mycorrhizal Associations,” Invasive Plant Science and Management, October-December 2012

Bats in Glen Canyon Park are being evicted NOW!

We are reprinting with permission an article about bats in San Francisco’s parks from the San Francisco Forest Alliance. The article reports observations of bats as well as a study of bat populations in San Francisco’s parks. The study found that both the number of bats as well as the number of species of bats was related to the amount of forest edge in each park and the availability of water. The study reports that the forest edge contains more insects which are the primary food of the bats.

We are posting this story today because hundreds of trees in Glen Canyon Park in which bats and many other creatures live are being destroyed as we speak. Here is a video of the destruction which started yesterday and continues today, along with a narrative of how and why this needless destruction is happening. Please watch this moving video to understand why we are so committed to opposing the pointless destruction of our trees by extremist agendas that are damaging the environment and harming the animals that live in our open spaces. (Edited to Add: And here is a video showing the second day of the demolition project.)

The study did not find any relationship between the number of bats nor the number of species of bats with the percent of native plant coverage. We speculate—although the study does not—that the absence of correlation between bat populations and native plant populations suggests that there are not more insects in native plants than at the forest edge. Although native plant advocates claim that more insects are found in native plants, this is yet more evidence that this claim is not true.

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Bats are insect-eating machines. According to the USGS, “Bats normally eat about half their weight in flying insects each night.” So even for those who don’t find these night-flying mammals charming, it’s good to know there are bats among us.

San Francisco has at least four species of bats, all of which eat insects. According to research by Jennifer Krauel, which involved recording bat sounds to determine which species they were, Mexican Free-tailed bats are the most common. Parks with water – like Glen Canyon – also have Yuma Myotis bats. The other two species she found (more rarely) were Western Red Bats, and Little Brown Bats, and she found them in just a couple of places.

Her research indicated that “amount of forest edge and distance to water were the factors best explaining species richness and foraging activity.” It also showed that bats in San Francisco remain active through the winter and don’t hibernate or move elsewhere.

If you’re interested in reading her paper, it’s here as a PDF: Jennifer Krauel thesis on bats in SF

BATS IN GLEN CANYON PARK

Glen Canyon’s bats are often visible at dusk. They’re most evident in the Fall, though they’ve been seen at other times of the year. (The pictures above are from February and April, those below from October.)

Here’s a note on bat-viewing from one visitor to Glen Canyon.

“It was late in the afternoon, and late in October. We were standing around the entrance to the park on Alms Rd. As dusk fell, bats emerged from the tall eucalyptus trees. Quite suddenly they were in the air right above us. I pulled out my camera, which is not really good in poor light but I tried to take some pictures anyway. Here’s one:

“They’re difficult to spot in the picture, but all those black smudges are bats that were moving too fast for my pocket-camera. Here’s the same picture, cropped, with the bats circled in yellow:

“They dispersed over the canyon. Here’s another picture from a few minutes later (and the one below it shows where the bats are).

“It was fantastic. I haven’t seen this many bats anywhere in San Francisco.”

LARGE TREES ARE IMPORTANT

We did a little research, and found a Stanford report that emphasized the importance of large trees to a particular species of bats, Yuma Myotis… bats that Krauel’s research had actually found in Glen Canyon Park.

“Yuma bats that forage in the preserve travel several miles to roost in large trees in Portola Valley and Woodside, suburban communities on the San Francisco Peninsula. The average diameter of the bats’ chosen trees is about a yard across — more than three times wider than the average tree in those areas.”

(The link to the abstract of the actual Stanford research paper is HERE.)

That’s the size of the big eucalyptus trees in Glen Canyon Park – including those that SFRPD wants to chop down.

WHY BATS MATTER

Bats are an important part of an eco-system, and fill a role few other creatures do: They hunt night-flying insects like mosquitoes that birds don’t catch because they’re sleeping. This is especially important now as West Nile virus, a mosquito-borne disease, has been spreading.

Having bats in a landscape contributes to its bio-diversity. All species of bats are protected in California.

(Some people are concerned that bats carry rabies – and it’s true no one should handle bats, especially grounded bats that may be sick, with their bare hands. But according to the California Department of Fish and Wildlife, less than 1% of bats are infected. [Click HERE to see their note.] The risk of getting rabies from a bat is less than the risk of being struck by lightning.)

HOW WILL SF RPD ENSURE THE PRESERVATION OF THE BATS?

We’re concerned about the impact of the planned tree removals on Glen Canyon’s bats.

All species of bats are protected, and removing the trees will impact their habitat by reducing the number of safe roosting spots, especially for Yuma Myotis bats that need both large trees and nearness to water.
The contractor will be chopping down the trees in the daytime. Bats roosting there are likely to be killed – if not in the process of the tree-felling, by being forced to fly blinded and confused in the daytime and fall prey to hawks, crows and ravens.

How is SF RPD going to ensure the protection of these bats?

And in what ways will felling large trees near the stream alter the ecology of the canyon?

“It’s not nice to fool Mother Nature”

U.S. Fish & Wildlife Service recently announced that after a 25-year effort, they are finally giving up on the fantasy that they can relocate otters from the coast of California to one of the Channel Islands off the coast. From 1987 to 1991, they captured and relocated 140 otters in a futile attempt to create a “no-otter zone.” (1)

Only 40 otters remain near the Channel Islands. Fish & Wildlife claims that most of the otters returned to the coast. We’ll never know how many otters died in the process of relocation and subsequent repatriation. Clearly, even if they survived the pointless ordeal, they didn’t benefit from it.

Otters were nearly hunted to extinction because of their soft fur. Their population plummeted from 16,000 in the late 1700s to only 50 in the 1930s. They were listed by the Endangered Species Act as a threatened species in 1977 and their population has stabilized at about 2,800.

Because of their status as a legally protected species, U.S. Fish & Wildlife decided to move them based on their belief that they would be safer. They claimed to be concerned that the otters might be harmed by off-shore oil drilling. One wonders if their concern might have had more to do with the fishermen who say that otters are depriving them of their catch of abalone and sea urchins.

Fish & Wildlife published a study of their project in 2005, which acknowledged the failure of the effort, yet it took 7 years for them to get around to officially ending it.

Killing one animal to save another

Such attempts to control nature and the animals that live in it are the stock and trade of U.S. Fish & Wildlife as well as their colleagues in state agencies with a similar mission. Here are a couple of local examples.

The spotted owl was given endangered species status over 25 years ago. Logging was substantially reduced in the Pacific Northwest in an effort to save the habitat of the spotted owl, with devastating consequences for the timber-based economy. Despite that effort, the population of spotted owls declined over 40% in the past 25 years.

So, now US Fish & Wildlife has selected a new scapegoat for the decline of the spotted owl population. They have decided that another owl, the barred owl, is the culprit. The barred owl is larger and its range is apparently expanding. So, in its infinite wisdom, Fish & Wildlife recently announced that it will begin shooting barred owls where they don’t “belong” based on their assumption that the spotted owl will benefit from the removal of its competitor. (2)

Carpet bombing with rodenticides

As crazy as the plan to shoot barred owls is, here’s a plan that strikes us even worse. In April 2011, U.S. Fish & Wildlife announced its intention to evaluate a plan to aerial bomb the Farallon Islands off the coast of San Francisco with rodenticides to kill resident mice. (3)

Here’s their logic for this strategy: the mice are eaten by burrowing owls which don’t “belong” on the Farallones, in their opinion. They claim that they don’t want to kill the burrowing owls because they acknowledge that they are just as rare in their historic range as the birds they claim will be saved by this bizarre plan. They claim that when the burrowing owls eat all the mice, they start eating the eggs of the ashy storm petrel which is an equally rare bird, but it “belongs” on the Farallones, so its perceived needs trump those of the equally rare burrowing owl. They believe that if the mice are killed, the burrowing owls will return to where Fish & Wildlife believes they belong.

There is so much wrong with this plan that it’s difficult to know where to start. The Farallones are an important bird sanctuary, home to many species of birds many of which are rare. Can Fish & Wildlife guarantee that the burrowing owl is the only species of bird that will eat the poisoned mice? How many burrowing owls will die from eating the poisoned mice? If they don’t die, won’t they eat even more eggs of the storm petrel? Will the death of the mice deprive other species of birds of their food? As the rodenticide washes off the islands into the ocean, will it kill the marine life around the island? Will it enter the food web of the entire island, killing unintended targets such as the birds that eat fish?

As crazy as this plan sounds, it is not a new strategy for Fish & Wildlife. In 2008, 46 tons of rodenticides were dumped on an island in the Aleutian chain off the coast of Alaska. That carpet bombing is known to have killed a total of 420 birds, including 40 bald eagles. (4)

The outcry about the birds being killed by rodenticides has been getting louder recently. The San Francisco Chronicle reports that a coalition of wildlife and public health advocates has asked California’s regulator of pesticides to take rosenticides off the market. We hope these pleas for sanity will be heeded before the Farallones are bombed with rodenticides.

Nature is on the move

Just as humans have moved around the Earth in search of more hospitable conditions—more food, better climate, less competition—animals have done the same. Now humans have decided that the animals must stay put. Wherever they existed in the historic past is where they “belong.” When animals move, man has decided they are “invasive” and they must be stopped.

Man’s war on invasive species is accelerating because as the climate changes there is greater pressure on animals to move to find the food and habitat they need and on plants to find suitable growing conditions. Humans are apparently unwilling or unable to do anything to stop climate change, yet they are willing and able to try to prevent plants and animals from adjusting to climate change.

As senseless as it seems to deprive plants and animals of their survival mechanisms, this harmful approach has been immortalized in U.S. law by the Endangered Species Act. The ESA is about 40 years old and was enacted at a time when the consequences of climate change were largely unknown. It defines endangered species as any plant or animal that becomes rare within its historic range. So, for example, if an animal or plant moves in response to climate change, it is often designated as an endangered species even though it may be plentiful in its new home to which it is better adapted. And Fish & Wildlife comes to its “rescue” by trying to force it to return to its historic range to which it is no longer adapted.

As we pondered this conundrum, we were reminded of a television commercial in 1970. Mother Nature is telling stories to her animal friends in the forest, when someone hands her a tub of margarine to taste. She smiles sweetly and congratulates herself on how delicious butter is. She is informed that it isn’t butter, but rather an artificial substitute. She rises from her throne, raises her voice to scold, shoots lightning from her fingers and warns us, “It’s not nice to fool Mother Nature.” (see this charming video here).

Will nature punish humans for their refusal to allow it to change as needed to survive? No, not literally, of course, but perhaps we will suffer the unintended consequences of our arrogant attempts to control natural processes we do not understand.

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(1) Peter Fimrite, “Feds scrap ‘dumb idea’ of relocating otters,” San Francisco Chronicle, December 18, 2012

(2) Associated Press, “U.S. plans to kill Barred owls to save spotted owls,” San Francisco Chronicle, February 29, 2012

(3) Kelly Zito, “Pesticide bombing of Farallones mice stirs debate,” San Francisco Chronicle, May 12, 2011

(4) Peter Fimrite, “Concern over fallout of bombing mice,” San Francisco Chronicle, October 17, 2011

Mistletoe: Another “bad plant” is exonerated

Mistletoe has a mixed reputation. On the one hand, we associate it with the Christmas folk tradition of obliging those who stand beneath it to be kissed. But foresters have always considered it a parasite that sucks the life from the trees in which it lives. Today we have the pleasure of reporting the result of a study in Australia which exonerates mistletoe of this crime.* It’s our Christmas gift to our readers.

David Watson, an ecologist at Sturt University in New South Wales, Australia, had long suspected that his favorite plant, mistletoe didn’t deserve its reputation as a harmful plant. In 2004 he set out to prove his hunch. He removed all the mistletoe from 17 woodlands and compared them with 11 woodlands in which the mistletoe remained and 12 woodlands in which there was no naturally occurring mistletoe.

Removing the mistletoe was a huge task which took two years. A dozen people, using cherry-pickers and clippers removed 40 tons of mistletoe. They waited three years to study the differences in the three types of forest.

They found that there were more birds, mammals, and reptiles in the forests where the mistletoe remained. But the most significant difference in the three types of forest was that the number of insects on the forest floor where the mistletoe remained was much greater.

Mistletoe in silver birch. Creative Commons

There are more insects on the forest floor where mistletoe resides because the leaves of the mistletoe contain more nutrients than the leaves of the tree that it occupies. The tree uses the water and nutrients in its leaves before the leaves fall, whereas the fallen leaves of the mistletoe are both more abundant and contain more nutrients. The leaves of the mistletoe also fall throughout the year when many of the trees are dormant. Hence, there’s more food on the forest floor occupied by mistletoe for the insects that live there.

Mistletoe is found everywhere in the world except Antarctica. There are 1,400 species of mistletoe in 5 families. Fossil pollen grains indicate that mistletoe has existed in North America for millions of years. Although a controlled experiment has not been done in North America, some scientists have noticed the benefits of mistletoe to forest life. David Shaw, at Oregon State University, has noticed that the endangered northern spotted owl nests in mistletoe.

Science tests our assumptions

This study of mistletoe is a nifty little example of the power of science to test our assumptions. Our assumptions are often mistaken. We should keep an open mind about any assumption that has not been tested empirically.

Native plant advocates assume that native plants are inherently superior to non-natives and conversely, that non-native plants are not beneficial to wildlife. Their assumptions are not supported by scientific studies. In fact, when their assumptions are tested empirically, they are often proven to be wrong. The native plant movement is an ideology that is not based on science. It is a horticultural preference which should compete in the marketplace of ideas with all other horticultural preferences.

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*Alanna Mitchell, “Beyond the kiss, Mistletoe Helps Feed Forests, Study Suggests,” New York Times, December 17, 2012. Available here.

Acacia: Another Australian tree caught in the cross hairs of nativism

Webmaster: We are republishing, with permission, a post from the website of Christian Kull, Associate Professor of Geography and Environmental Science at Monash University in Melbourne Australia. He is also Adjunct Professor at the University of the South Pacific. He is presently based in Suva, Fiji, where his wife is employed by a division of the Secretariat of the Pacific Community. (We have added a few edits for an American audience.)

We have read the debate in scientific journals between Professor Kull and his colleague, Jacques Tassin, with Tim Low, which is described in this post. It sounded very familiar to us. On the one hand, Kull and Tassin wish to consider the economic and environmental benefits of acacia. Their pragmatic evaluation of acacia is attacked by Tim Low, using the same alarmist arguments that we hear in the San Francisco Bay Area about another Australian tree, the eucalyptus.

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Are Australian acacias planted overseas miracle plants for rural development, or are they the worst kind of environmental weeds? The battle lines appear rather stark at times. At least when one reads environmentalist Tim Low’s rebuttal to a critique that Jacques Tassin and I wrote of his views. We thought our statement to be tempered and tried to build a reasonable case for responsible use of exotic agroforestry trees (see also previous blog). But Low calls us “in denial about dangerous aid,” flogs a misplaced example about mesquite in an argument about acacia, all the time preaching his argument to the converted in the journal Biological Invasions. Low has even taken his views to an online editorial on the Australian Broadcasting Corp website and has promoted his views to the Herald Sun (link).

Meanwhile, in Vietnam, an entirely different story is developing. On 2 November, there was a small seminar and dinner in Hanoi, Vietnam celebrating the contributions of Australian and Vietnamese scientists to the forestry sector, primarily through the promotion of Australian acacia species. The Vietnamese Government awarded medals to Sadanandan Nambiar, Chris Harwood, Khongsak Pinyopusarerk, Rod Griffin and Stephen Midgley for “contributions to Vietnam’s forest development.” Australian acacias are now a common part of Vietnam’s rural landscape, rehabilitating denuded landscapes, and providing wood for industry and fuel. Australian aid (via CSIRO, AusAID, and ACIAR) played a role in supporting such initiatives since 1987, working together with Vietnamese partners like the Research Centre of Forest Tree Improvement and the Forest Science Institute of Vietnam.

Tea grown in shade of acacia in Vietnam. Photo by Chris Harwood

According to Stephen Midgley, there are now about 900,000 hectares of Australian acacia plantations in Vietnam (about the same area as the Californian Pinus radiata [Monterey pine] in Australia). Just last year, an estimated 120,000 hectares of acacias were planted in Vietnam – some 70% by smallholders [private property owners]. Acacias have been used as nurse crops to rehabilitate native forest areas; examples include the protection forests of Hai Van Pass and the Perfumed River catchment behind Hue. Acacias are now a valuable commercial asset, as hardwood woodchips and as furniture wood. Product value exceeded US$1.5 billion in 2011, with some US$400 million returning directly to the pockets of the growers, leading to improvement to livelihoods among acacia-growing communities.

An ecologist may look at this situation and worry that the acacias in Vietnam are going to ‘explode’ in the future, becoming problematic pests or replacing ‘natural’ forest. That is, they will become too successful for their own good. Indeed, apparently the weediness of acacias will be addressed to some extent at the upcoming IUFRO acacia sylviculture working party meeting in Vietnam. Chris Harwood, of Australia’s research agency CSIRO, wrote to me:

“On my just-completed trip to Vietnam I had a careful look (as I always do) in the farming landscapes of northern, central and southern Vietnam for signs of acacias spreading as weeds. There are no such signs. All the farming land is too intensively cultivated (Vietnam has a land area of 33m ha and a population of 87m), and all the acacias in the landscape are planted rather than naturally regenerated, except for very occasional patches of vacant ground which may have a few ‘volunteer’ acacia seedlings but which will soon go under cultivation. Quite large areas formerly under acacia plantations in southern Vietnam have been converted to rubber plantations during the last 5 years, with no evident difficulty. In the north, tea is successfully grown under Acacia mangium. The only caveat regarding weediness in Vietnam is that care must be taken when planting adjacent to native ecosystems to ensure that acacias do not spread into them. But this is a manageable potential problem and is just not an issue for the vast majority of acacia plantations that do not abut natural ecosystems.”

Acacia and cucumber field in Vietnam. Photo by Chris Harwood

In addition to ecological questions about invasion potential, social scientists may ask about how access to land and other rural power relations are altered by such forestry development. Indeed they have already (link). But the point here might be that shouting from diametrically opposed ideological camps is probably not the best way to move forward. In this case, there is a will to plant acacias (what combination of government diktat and social consensus I don’t know) and they are already deeply incorporated into the physical and socio-economic landscape. In addition to shaping the already very anthropogenic landscape by farming rice, other crops, and tree crops like rubber (over 1 million hectares), the Vietnamese are farming acacias. The question then, instead of “go acacia go” or “doom is coming,” is how farmers, foresters, villager leaders, government agents, and scientists might each in their own way address the questions of the future of Vietnam’s regional landscapes – what values are important, what are the options, what are the constraints and potential problems, what does the evidence show. It is this kind of measured approach Jacques Tassin and I tried to make in our response to Tim Low.

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Webmaster: We believe that the debate we are engaged in with native plant advocates should be a land-use decision. This should be a civil debate, which in a democratic society should result in a decision that reflects the wishes of an entire community.

Unfortunately, native plant advocates seem to believe that their demand that non-native trees and plants be destroyed is a moral imperative. Although they claim environmental damage from non-native trees, they are unable to provide the scientific evidence to support that claim. In the absence of such evidence, their demands are just an imposition of their gardening preferences on the public. The tactics they use to impose their will are inconsistent with their claim that they are on the moral high-ground and the methods they use to eradicate non-native species are also inconsistent with their claim that they are benefiting the environment.

Our urban forest is under siege

P1010683 — The urban forest on Mt. Davidson is slated for destruction.

According to California Trees (1) the US Forest Service has determined that tree cover in the country’s urban areas is decreasing by 4 million trees a year. Although no research has been done on tree loss throughout California, the US Forest Service reported a one-percent decline in trees and shrubs in Los Angeles despite a big campaign to plant one million trees there.

You might think that the loss of trees in urban areas is the result of increasing development and you would probably be at least partially correct. But many trees are lost for more trivial reasons that we think could be easily prevented. Here are some local examples of trees in the Bay Area that were needlessly destroyed or soon will be.

The City of Oakland has a “view ordinance” which guarantees homeowners the preservation of their view at the time they purchased their home. This view ordinance was invoked by a resident in the Oakland hills who demanded that her neighbor and the City of Oakland destroy trees obstructing her view. Her neighbor purchased her house because of its forested view. Yet, the desire for a forested view was trumped by her neighbor’s desire for a treeless view. The law required that 25 trees be destroyed on private property and 21 trees on city property in order to restore the view of a 95-year old property owner who no longer lives in her home. When trees are destroyed for such trivial reasons, we should not be surprised by the following compendium of absurd excuses to destroy trees. (The story is here.)
The people of San Francisco are trying to prevent the destruction of their urban forest which is almost entirely non-native. The City of San Francisco is systematically destroying non-native trees in order to return the landscape to its historical origins as grassland and dune scrub. The latest battle in this long war is a particular park, Glen Canyon, in which the City proposes to destroy about 160 trees in the short -run and 300 trees in the long-run. A handful of the trees are hazardous and aren’t disputed, but most have been evaluated as “poor suitability” which is the latest euphemism used by native plant advocates to describe non-native trees. They propose to replace most of the trees with native shrubs and a few tall trees that are native to California, but not to San Francisco, such as Douglas Fir and Cottonwoods. It remains to be seen if either of these species will survive in San Francisco. Douglas Fir requires more rainfall than San Francisco receives and Cottonwoods are hot-climate trees which don’t tolerate mild temperatures without seasonal fluctuations. We suspect that is the strategy, i.e., to plant trees for the sole purpose of placating the public without any intention that the trees will survive. (The story is here.)
The space shuttle Endeavor was recently retired from service. Its permanent home is now a museum in Los Angeles, where 400 street trees were destroyed to accommodate the delivery of the space shuttle from the airport to the museum. The neighbors were not pleased, as you might imagine. They unfortunately live in a blighted part of Los Angeles, so they didn’t have the clout needed to save their trees. Do you think these trees would have been destroyed in Beverly Hills? We doubt it. (The story is here.)
The neighbors of Dimond Park in Oakland are trying to save the trees in their park from being destroyed by a “restoration.” We often marvel at the use of the word “restoration” to describe projects which are more accurately described as “destruction.” This is yet another native plant project, which is hell bent to remake nature to its liking. In this case 42 trees would be destroyed, of which 27 are native, including 17 redwood trees. Please help the neighbors save their trees by signing their petition which is available here.
Finally, we share the story of a property owner on 65^th St in Oakland who with a great deal of courage and tenacity was able to save most of the street trees on her block from being destroyed by the City of Oakland. The trees weren’t posted as required by Oakland’s ordinance. The crew who came to cut them down couldn’t tell her why they were being cut down, nor could they tell her who owned the trees. We encourage you to read her story because it will give you a brief lesson on the difficulty of advocating against the needless destruction of trees.

Deforestation causes climate change

We have been accumulating these stories in the past few months, but are finally inspired to share them with our readers because of the recent storm on the East Coast, Sandy, which caused over $50 billion in damage and the lives of over 100 people. What’s the connection? The connection is that Sandy has finally forced people to take the threats of climate change more seriously.

When will this new interest in climate change translate to an interest in saving our trees? Probably not soon, because few people understand that globally, deforestation contributes 20% of greenhouse gases that cause climate change. The public and its elected representatives are focused primarily on transportation as the source of climate change. Transportation contributes only 10% of greenhouse gases globally.

Here in California, we are gearing up to put our climate change law (AB 32) into action by creating a cap and trade auction which will enable emitters of greenhouse gases to purchase carbon offsets. Ironically, one of the things that carbon emitters can do to offset their contribution to greenhouse gases is to plant trees. Yet, those who destroy trees are not being required to purchase carbon offsets. Until the people who destroy trees are required to pay for the damage they do to the environment, we are unlikely to see a change in the cavalier attitude that governments seem to have about destroying trees.

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(1) California Trees, Winter 2012, Vol 20, no 2

Ecosystem processes are comparable in native and non-native forests in Hawaii

Hawaiian_forest_-_Flickr_-_USDAgov — Native Hawaiian forest. Creative Commons Attribution

Joseph Mascaro is one of the scientists Emma Marris interviewed for her ground-breaking book, Rambunctious Garden. (1) Marris visited Mascaro on the Big Island of Hawaii, where he was studying the forests, comparing native with “novel” forests, the name given to ecosystems composed of both native and introduced species of plants.

According to Marris, Mascaro considers Ariel Lugo his mentor. Lugo is a US Forest Service scientist living and working in Puerto Rico. He is one of the first scientists to observe and report that non-native forests in Puerto Rico are performing important ecological functions and benefiting native forests by restoring depleted agricultural soils and providing shelter to native seedlings.

Lugo, like many native plant advocates, received his education in ecology at a time when there was deep suspicion of introduced species. The conventional wisdom was that introduced species were competitors of preferred native species, that they were inferior members of an ecosystem and that they would eventually dominate and replace their native predecessors.

When Lugo’s team reported that the understory in the non-native forest was so dense that it made the forest impenetrable, he was incredulous. Slowly, the reality of the non-native forest penetrated the prejudices of his training. He submitted his findings for publication repeatedly. After a lengthy debate, his study was finally published in 1992. He still considers himself an outlier amongst his colleagues in the Forest Service.

Joseph Mascaro is now a Postdoctoral Associate at the Carnegie Institution for Science in Stanford, California. His study of the novel forests of Hawaiian lowland rain forests has recently been published: “Novel forests maintain ecosystem processes after the decline of native tree species.” (2) We will do our layman’s best to report his main findings.

Judging the forest by the functions it performs

The scientific community seems to agree that introduced plant species have resulted in a net increase in species on the Hawaiian Islands: “Seventy-one vascular plant species are known to have become extinct in Hawaii over the past ~1700 years, while at least 1,090 introduced plant species have become naturalized during this period: an approximate doubling of its pre-human contact flora.” (2)

Mascaro’s study asks and answers the question, what are the functional implications of increased diversity due to invasion? He proposes and tests three hypotheses:

Species richness and diversity are greater in novel forests than native forests in lowland Hawaii.
Basic measures of ecological functions of novel forests meet or exceed measures in native forests. He used these basic measures:
- Aboveground and belowground production of biomass, called productivity
- Aboveground and belowground storage of carbon
- Cycling (or turnover) of nitrogen and phosphorous between soil, trees, and leaf litter.
- Because forest establishment in Hawaii begins on barren lava flows on which there is no available nitrogen and it takes several centuries to accumulate the nitrogen needed by native trees, the disparity between the functioning of novel and native forests are greatest on younger lava flows where novel forests are composed of nitrogen-fixing tree species.

He reports his findings: “At local scales, we found that novel forests had significantly higher tree species richness and higher diversity of dominant tree species. We further found that aboveground biomass, productivity, nutrient turnover (as measured by soil-available and litter-cycled nitrogen and phosphorus) and belowground carbon storage either did not differ significantly or were significantly greater in novel relative to native forests.” (2) Our interpretation of this study is that the novel forests of the lowland rain forests of Hawaii maintain basic functioning where native forests are now absent and that the novel forest facilitates the revegetation of barren lava flows by creating fertile soil.

800px-Hawaii_Cape_Kumukahi_lava_flow — Barren Hawaiian lava flow. Creative Commons Attribution

He also speculated that “Because large portions of the Earth’s surface are undergoing similar transitions from native to novel ecosystems, our results are likely to be broadly applicable.” (2) It is this conclusion that his findings can be generalized to other locations that brought Joseph Mascaro’s study to our attention.

Mascaro recently wrote to the Webmaster of the Save Mount Sutro Forest website and sent his study. He lives in San Francisco and drives over Mt. Sutro daily, on his way to work. Mascaro told the Save Sutro Webmaster, “I wanted to let you know that your website and effort are much appreciated. As a practicing ecologist, I find it bewildering that efforts to restore native plant communities (some of which I find very important) would be directed at a diverse, old-growth, functioning ecosystem smack in the middle of one of the largest cities in the country….Cases like Sutro are often emotional and controversial, and while I don’t disparage anyone’s view, I tend to think that great pause must be taken before destroying something that is centuries old. I hope you will continue your effort.” (quoted with permission)

We are grateful to Joseph Mascaro for his research on the novel forests of Hawaii and for expressing his opinion of the value of the forest on Mt. Sutro. We are also grateful to the Webmaster of Save Sutro Forest for her insightful and articulate defense of the Sutro Forest.

The evolution of ecology

We began this post with the observation that scientists have found it difficult to report their findings about novel ecosystems that are not consistent with their educational training. When we expect to see something, it is often difficult for us to see something that contradicts those expectations. We commend scientists such as Ariel Lugo for reporting his observations, although they weren’t consistent with his training.

We are also pleased to report that we have observed, first-hand, a change in the training of university students in ecology. We attended two sessions of an undergraduate seminar in a local, major university. That seminar is reading and evaluating Rambunctious Garden. The students were entirely receptive to the revision of traditionally negative judgments of introduced species. That revision is the main theme of Rambunctious Garden. These students are the next generation of ecologists. They are the beginning of a new conventional wisdom about the role of introduced species in our ecosystems.

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(1) Emma Marris, Rambunctious Garden, Bloomsbury, 2011

(2) Joseph Mascaro, R. Flint Hughes, Stefan A. Schnitzer, “Novel forests maintain ecosystem processes after the decline of native tree species,” Ecological Monographs, 82(2), 2012, pp. 221-228 by Ecological Society of America

Center for Biological Diversity is about power and control

We try to give people the benefit of the doubt. We assume that native plant advocates believe what they say even when we know what they’re saying isn’t true. We assume they share our commitment to protecting the environment even though we don’t agree about how to achieve that goal.

When the Center for Biological Diversity (CBD) was required by the Arizona Supreme Court to pay $600,000 in punitive damages for fabricating fraudulent evidence to support their unsuccessful effort to take federal grazing rights from a rancher in Arizona, we assumed it was just an example of over-zealous environmentalism. People who believe they are on an important mission sometimes think the means they use to achieve their goals are justified by the righteous ends of their cause.

However, recent events have forced us to reconsider our generous interpretation of CBD’s motives. In particular, we find the Center for Biological Diversity’s action and inaction on these two local issues contradictory:

On one hand, CBD filed for endangered status for the Franciscan manzanita. CBD’s clone, Wild Equity (founded by a former employee of CBD), sued when endangered status was delayed. They demanded the designation of critical habitat—including 196 acres of San Francisco’s public parks– for a plant which is likely a hybrid of one of the most common species of manzanita and will require dangerous and polluting wildfires to reproduce. This seems consistent with CBD’s long track-record of aggressively protecting rare plants and animals despite negative impact on humans.
On the other hand, CBD has thus far done nothing on behalf of the endangered Clapper Rail. It has been over a year since studies have shown that the eradication of non-native Spartina marsh grass in San Francisco Bay has decimated the small population of this rare bird. The assumption is that the Rail is exposed to its predators–particularly during nesting season–by eradication of dense, year-round cover provided by Spartina. It’s also possible that the pesticide (imazapyr) used to eradicate Spartina is a factor, because the effect of imazapyr on shore birds has not been tested. The absence of action on behalf of the Rail seems inconsistent with CBD’s extreme actions on behalf of other endangered plants and animals.

Is Center for Biological Diversity motivated by money?

So how do we reconcile these seemingly inconsistent actions vs. inactions of CBD? What motivates their selection of particular species of plants and animals for protection?

Ted Williams calls himself an “environmental extremist.” He is the author of a regular column in Audubon Magazine which is appropriately entitled, “Incite.” One of Williams’ articles demonizing eucalyptus is typical of the provocative approach of his column. In that article, he fabricated “data” about bird deaths to justify the crusade to eradicate eucalypts.

Williams is proud of his credentials as an environmental provocateur and he uses those credentials to defend his criticism of Center for Biological Diversity in an article in High Country News (1). He expresses his opinion that CBD is motivated by money. He points out that CBD has filed hundreds of suits against the federal government, using environmental laws, such as the Endangered Species Act, and that every time it wins it collects attorney fees from the federal government. The cost and number of these suits has become a major obstacle to US Fish & Wildlife and the Environmental Protection Agency in fulfilling their mandate to protect rare species.

Although these accusations are accurate, we don’t think this is an adequate explanation for CBD’s choice of issues to pursue. We turn to the New York Times to put this accusation into perspective. The Times reports (2) that CBD had filed 700 lawsuits when the article was published in March 2010, and they were successful in those suits 93% of the time. Those suits forced the government to list 350 endangered species and designate 120 million acres of critical habitat for their recovery.

However, revenue generated by the success of these suits was only $1.4 million in 2008, compared with $7.6 million from contributions and grants. In other words, only 16% of CBD’s revenue in 2008 came from their suits against the federal government.

Furthermore, the founder and Executive Director of CBD earned $116,000 in 2008, which doesn’t seem out of line for an organization with over 60 employees and offices all over the country (including the San Francisco Bay Area).

We don’t think the leadership of CBD is motivated by money.

It’s about power and control

We turn to the New Yorker magazine (3) to understand and explain the motivation of Center for Biological Diversity and its local ally, Wild Equity. In 1999, the New Yorker published an in-depth study of the leadership of CBD entitled, “No People Allowed.”

The article reports the creation of CBD and its early history in the southwest where it was founded and is still headquartered. Their initial efforts were direct-action, typical of traditional environmental organizations; then they discovered the power of the law: “’We’re crazy to sit in trees when there’s this incredible law where we can make people do whatever we want,’” said Robin Silver, one of the founders of CBD.

Using federal environmental laws, they apparently brought the timber industry in the southwest to a virtual halt and they were making similar progress in eliminating all grazing in the southwest when the article was published. Perhaps there was some benefit to the environment, but there was also significant economic loss to the human community in the southwest, according to the New Yorker.

So, what does CBD want? The New Yorker tells us that the founder’s deconstructionist philosophy is “a decentering and disempowering of the human.” Their goal is described: “…the center is endeavoring to undo the dominion of man over animals and plants…the only way to get to the desired state is to deconstruct stuff that exists in the world: legal arrangements, social and economic forms, and even physical structures.” CBD’s Executive Director tells us his motivation in the New Yorker article as well as the long term goal of CBD: “[Kieran] Suckling cheerfully admitted that he’s ‘using one side of industrial society against itself,’ but only temporarily; in the long run, he says, there will be a new order in which plants and animals are part of the polity. For example, legal proceedings could be conducted outdoors—in which case ‘the trees will make themselves felt.’”

We find the reference to the desires of trees particularly interesting. Apparently Mr. Suckling believes he speaks for the trees. What about the non-native trees which CBD demands we destroy on behalf of other plants and animals which it prefers? Mr. Suckling apparently considers himself the spokesperson for just particular trees of his choosing. Apparently the rights of trees will be limited to native trees when CBD has successfully established this new order.

Mountain View Cemetery - eucalyptus — “Bad” tree must go.

Mr. Suckling also implies that CBD’s control of the environment is only temporary until the new order is established in which plants and animals are in control. This reminds us of a similar fantasy about a new social and economic model which was originally proposed by Karl Marx. In creating the concept of communism, he envisioned a temporary dictatorship of elites which would eventually be ceded to a “dictatorship of the proletariat.” The world has now witnessed many attempts to install communism as the governing economic model, but we have not seen the dictatorship of elites willingly cede their power to the people.

This quote of CBD’s Executive Director from Ted Williams’ article, also helps us to understand why CBD sues the federal government to achieve their goals: “’They [employees of federal agencies] feel like their careers are being mocked and destroyed—and they are,’ he told the High Country News. ‘So they become much more willing to play by our rules.’” In other words, suing—and the threat of suit—is CBD’s means of controlling the federal agencies that are responsible for protecting the environment, i.e., forcing them to do what CBD wants.

Humans will always be in control of land-use decisions. It’s only a question of which humans are in control and CBD intends to be the humans in control. If we hand them that power, we will find it difficult to wrest it from them if we decide they are not using that power wisely or fairly.

We can’t defend all of the activities of humans when we damage the environment to suit our purposes. However, we don’t think the Center for Biological Diversity would be a better steward of our land. Even if they were capable of wise land-use decisions, we are unwilling to suspend democratic methods of making those decisions. As human society repeatedly demonstrates, absolute power corrupts absolutely. We are no more willing to hand our fate to Center for Biological Diversity than to any other despot, benevolent or not.

We invite Center for Biological Diversity to prove us wrong

We would like Center for Biological Diversity to prove us wrong. CBD can demonstrate that their motivation is not simply the confiscation of public land from human use as a means of destroying human society and civilization. They can start by filing suit on behalf of the endangered Clapper Rail to stop the pointless and destructive eradication of non-native Spartina in San Francisco Bay, using a toxic pesticide about which little is known. CBD can demonstrate their commitment to protecting animals even if humans are not punished by that effort.

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(1) Ted Williams, “Extreme Green,” High Country News, May 21, 2011

(2) Anne Mulkern, et. al., “Brazen Environmental Upstart Brings Legal Muscle, Nerve in Climate Debate,” New York Times, March 30, 2010.

(3) Nicholas Lemann, “No People Allowed,” New Yorker, November 22, 1999.

More evidence that eucalypts are not invasive

Eucalyptus, Mountain View Cemetery, Oakland

We have provided our readers with photographic evidence that eucalypts are not invasive in the San Francisco Bay Area (click here and here). Now we are going to tell you about more confirmation of this fact from a reputable source that will be difficult for native plant advocates to ignore: Encyclopedia of Biological Invasions.

The Encyclopedia was edited by Daniel Simberloff (U of Tennessee) and Marcel Rejmanek (UC Davis) and published by UC Berkeley Press in 2011. Many of our readers will recognize Simberloff as a prominent scientist in invasion biology. He is responsible for the “invasional meltdown” hypothesis which is central to invasion biology. A recent survey of empirical tests of the hypotheses of invasion biology found that there is considerable support for the “invasional meltdown” hypothesis, but that support is declining.

Professor Simberloff has aggressively defended the assumptions of invasion biology against scientists who think that a revision of those assumptions is required by recent empirical evidence. When Professor Mark Davis and 18 of his colleagues in ecology signed a comment in the Nature journal entitled, “Don’t judge species on their origins,” Professor Simberloff promptly recruited 140 of his colleagues to publish a rebuttal.

We establish Professor Simberloff’s credentials for our readers as a scientist who firmly believes that non-native species are a serious threat to biodiversity so that native plant advocates will consider him a credible source of information regarding eucalyptus.

“Eucalypts” according to the Encyclopedia of Biological Invasions

According to the Encyclopedia of Biological Invasions, eucalypts are “some of the most important solid timber and paper pulp forestry trees in the world.” There are about 40 million acres of eucalypts planted in tropical, sub-tropical, and temperate countries. The predominant species of eucalyptus in the Bay Area, Blue Gum (E. globulus), is grown in 13 countries in addition to the US and Australia. About 70 species of eucalypts are naturalized outside their native ranges. “However, given the extent of cultivation, eucalypts are markedly less invasive than many other widely cultivated trees and shrubs…they have been orders of magnitude less successful as invaders than pines and several other widely planted trees…Where eucalypts have invaded, they have very seldom spread considerable distances from planting sites, and their regeneration is frequently sporadic. “ (1)

Although the Encyclopedia admits to being puzzled by why eucalypts aren’t invasive, it offers “three major reasons for the limited invasiveness of eucalypts:”

Reason One: Seed dispersal of eucalypts is limited

The seeds of eucalypts have no natural means of dispersal, such as fleshy tissue which can function as wings on the wind. Tests have shown that the seeds “are dispersed over quite short distances.” (1) “Seed dispersal is mainly by wind or gravity and is virtually limited to twice the tree height.” (2)

The seeds of the Blue Gum are encapsulated in a woody pod which makes them inedible to birds and mammals. So, the seeds of the Blue Gum are not dispersed by animals.

Reason Two: High mortality of eucalyptus seedlings

Eucalyptus seedlings die quickly if they don’t establish roots in moist soil quickly. If the soil is too moist they are susceptible to destruction by fungus. If there is too much leaf litter or there is an understory, they are unlikely to find the quick access to the soil they need to survive. There is a narrow range of conditions needed to successfully establish eucalyptus seedlings.

Reason Three: Lack of compatible mycorrhizal fungi

Mycorrhizal fungi exist in the soil and sometimes form a symbiotic relationship with the roots of plants. They are often essential to the health of the plant because they facilitate the absorption of water and nutrients by the plant. Some biologists speculate that the specific species of mycorrhizal fungi needed for successful seedling development have not been exported with the eucalypts to foreign soils.

A balanced discussion of the pros and cons of eucalypts

Given the strong commitment of the authors of the Encyclopedia of Biological Invasions to invasion biology, we are impressed with its even-handed discussion of the ecological pros and cons of eucalypts as well as its recognition of the lack of hard data to support a particular conclusion: “Conclusions about positive or negative environmental and economic impacts of eucalypts are often anecdotal, highly controversial and context dependent.”

The authors suggest that eucalypts not be planted near streams as the moving water is a means of seed dispersal. On the other hand, when planted on degraded soil, the eucalypts have provided a fuel source which reduces pressure on remnants of native forests. Eucalypts have been a valuable source of nectar for honey production all over the world. More birds are said to be found in native forests than eucalyptus forests in California. However, three times as many salamanders are found in the eucalyptus forests compared to native forests in California.

Eucalyptus%20Bee - Brian Stewart — Eucalyptus and honeybee. Painting by Brian Stewart

The Encyclopedia also addresses the controversial question of whether or not eucalypts are allelopathic, which means chemicals in their roots or leaves suppress the germination of the seeds of other plants. It reports that there is no conclusive evidence on this question. However, the accumulation of leaf litter is probably a physical barrier to the germination of seeds in its understory, which is not an allelopathic method of suppressing competition. This is clearly true of other trees as well. For example, the tannins present in both oak and eucalyptus leaves prevent the rapid break down of the leaf litter which accumulates and creates a physical barrier to competing vegetation. This is one of many examples of the characteristics that both native and non-native plants have in common.

The Encyclopedia attributes the flammability of the eucalyptus forest to leaf litter which is exacerbated in California by rare deep freezes. These deep freezes cause die-back of eucalypts, contributing to fuel loads. It makes no mention of the oiliness of leaves as a factor in flammability.

There has not been such a deep freeze in the East Bay in over 20 years and 20-year intervals of such weather events have been historically typical. These deep freezes do not occur on the San Francisco peninsula because its climate is moderated by the ocean and bay surrounding it. Its climate is therefore warmer in winter and cooler in summer. Therefore, this caveat about the flammability of eucalypts does not apply in San Francisco.

The myth lives on…..

Despite the fact that there is no evidence—scientific or experiential—that eucalypts are invasive, the myth lives on amongst the community of native plants advocates. We will continue to provide the evidence that eucalypts are not invasive. We hope that eventually the public will be sufficiently informed that they will become resistant to this claim of native plant advocates which is one of many myths used to justify the needless destruction of eucalypts.

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(1) Marcel Rejmanek and David Richardson, “Eucalypts,” in Encyclopedia of Biological Invasions, eds, Daniel Simberloff and Marcel Rejmanek, University of California Berkeley Press, 2011.

(2) Craig Hardner, et. al., “The Relationship between Cross Success and Spatial Proximity of Eucalypts Globulus ssp. Globulus Parents,” in Evolution, 212, 1998, 614-618.