Ecology – Page 35 – Conservation Sense and Nonsense

Conciliation Biology: Revising Conservation Biology

Our interest in invasion biology is primarily in its application, specifically to “restoration” projects. Therefore, as science revises the assumptions of invasion biology we are equally interested in the implications for ecological restorations.

Professor Scott Carroll (UC Davis) is a particularly good candidate to lead the way in revising ecological restoration practices, as informed by current scientific theories of invasion biology. His study of rapid evolution of the native soapberry bug to accommodate use of non-native vegetation puts him in the forefront of the effort to integrate evolutionary theory into invasion biology.

And so we introduce to our readers, Professor Carroll’s proposal that we turn from efforts to eradicate non-native species in favor of a new approach which manages the co-existence of native and non-native species. He calls this approach Conciliation Biology.*

Conciliation Biology is based on these premises:

The environment has been radically altered by the activities of humans
The environment will continue to change in the future.
It is not feasible to eradicate non-native species.
The cost of attempting to do so is prohibitive.

These are familiar themes on Million Trees and we will not belabor them in this post. Rather we will focus on those aspects of Professor Carroll’s proposal that are new to us.

Rapid evolution can resolve apparent ecological problems

Garlic mustard is an invasive non-native plant which tolerates shade and emits a powerful root toxin known to inhibit the germination of other plants, notably forest trees. This chemical tool to reduce competition is known as allelopathy, a weapon used by many plant species, both native and non-native.

Since garlic mustard arrived first in the eastern US and spread slowly west, scientists compared the allelopathic toxicity of a population of garlic mustard known to have arrived 50 or more years ago with a population which arrived only 10 years ago. The toxicity of the recently arrived garlic mustard was significantly greater than that of the older population. In fact, the understory and seedling germination were rebounding in the forest with the older population of garlic mustard.

In other words, science informs us that ecological problems caused by the arrival of new exotic species can resolve themselves over time.

New exotic species are sometimes better adapted to the changed environment

Professor Carroll cites a study of two aquatic species (Phragmite and Hydrilla) which provide superior ecological services than their native counterparts because of changes in the environment. The extreme weather events associated with climate change are subjecting our coasts to unprecedented storm surges. Native species of marsh grass are not as successful in protecting the coast against the ravages of these storm surges.

We have our own local example of the same phenomenon. Non-native Spartina marsh grass is being eradicated along the entire west coast of the country. It grows taller and thicker than native Spartina and it does not die back during the winter months as the native species does. Since storm surges occur during the winter months, surely the non-native Spartina provides superior protection to our coast. We have yet to see a scientific experiment which proves this point, but common sense tells us that it is a study that needs to be done, particularly since ornithologists have reported that the eradication of non-native Spartina has been harmful to our dwindling population of endangered California Clapper Rail.

The harmful effects of eradication efforts

We have seen many such harmful consequences of eradication efforts, but Professor Carroll provides his own example. Iberian rabbits are native to Spain. They were intentionally imported to Australia where they quickly became a problem. The Australians imported a virus from South America that killed the rabbits. The virus was also introduced to Britain for the same purpose. The virus has spread back to Spain where it is killing the rabbits in their native range. The rabbits are prey of several rare species of animals in Spain, including the Iberian lynx. The absence of their prey is now decimating those native predator populations as well.

Biological controls are one of many dangerous games being played by those who share in the fantasy that it is possible to eradicate non-native species without paying a price. Sometimes that price is greater than whatever cost may be associated with the non-native species.

Simply eradicating non-native species will not necessarily result in the return of natives

Professor Carroll tells us the story of the failed attempt to save the Large Blue butterfly in Britain from extinction to illustrate this point. This was apparently a spectacularly beautiful butterfly, and so the British spent 50 years trying to bring it back from extinction. They failed because they figured out too late that the butterfly is dependent upon an ant which lives only in heavily grazed vegetation. The ant population no longer existed within the range of the butterfly because grazing had long ago been abandoned.

How many other pointless efforts to reintroduce endangered species are there? We recently told our readers about the effort to reintroduce the endangered Mission Blue butterfly to Twin Peaks in San Francisco. This is a radically altered environment with high levels of nitrogen and carbon dioxide associated with the urban environment. The annual brush fires of pre-settlement San Francisco are no longer capable of sustaining the scrub required by the butterfly and the prescribed burns, which are the artificial equivalent, are not allowed in San Francisco. The scrub is therefore maintained with repeated applications of pesticides which are unlikely to benefit the endangered butterfly.

What is Conciliation Biology

Conservation biology has been “constrained by often futile efforts to restore historical communities, and [does] not appreciate the unavoidable and dynamic contributions of ongoing adaptive evolution.” * Conciliation biology proposes to address these shortcomings by:

Taking a longer-term view of the chronic effects of changes in the environment.
Making greater use of evolutionary theory
Fostering ongoing adaptation by accepting the hybridization that increases genetic variability
Identifying and supporting community mechanisms that increase resiliency
Improving the effectiveness of the science of invasion biology by using a multidisciplinary approach

How long will It take for this new approach to filter into the minds of those who are busily destroying non-native vegetation and damaging the environment in the process? How much damage will be done before these destructive methods are abandoned in favor of an approach that accommodates the reality, inevitability, and often the advantages of change?

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*Carroll, Scott, “Conciliation biology: the eco-evolutionary management of permanently invaded biotic systems,” Evolutionary Applications, 2011, 184-199.

Invasion Biology: The way forward

We’re following up on our previous post in which we reported that empirical studies do not support the hypotheses of invasion biology. In that case, six hypotheses of invasion biology were tested by empirical studies and largely failed. Furthermore, more recent studies are less supportive than older studies, indicating declining support for the assumptions of invasion biology.

Now we are going to tell you about a new publication by another team of scientists who challenged other assumptions about invasive plants and also conducted their own original research of one of the most basic assumptions of invasion biology: that invasions are facilitated by disturbance.

Wildfire in Bitterroot National Forest 2000 — Wildfire, Bitterroot National Park, 2000. Wildfires are a type of disturbance that has increased with global warming and drought.

We introduced our readers to the leader of this research team, Professor Angela Moles, in a recent post about the mounting evidence that attempts to eradicate non-native species are futile. Professor Moles (University of New South Wales, Australia ) gave a TED (Technology, Entertainment, Design) presentation in which she reported that introduced species have changed significantly since their introduction and that if they weren’t yet new species, they soon would be. She proposed that non-native plants in Australia be granted citizenship.

Professor Moles collaborated with 21 scientists all over the world (Uganda, Indonesia, Mexico, USA, Australia, New Zealand, Japan, Argentina, Estonia, New Zealand) in the study that resulted in a recently published article entitled, “Invasions: The trail behind, the path ahead, and a test of a disturbing idea.” *

The trail of invasion biology

As the title suggests, the article begins by reporting that after 30 years and 10,000 publications, invasion biology has tested many assumptions and found inconsistent evidence to support them:

The search for traits of introduced plants that predict invasiveness has been a dead end: “…it is not currently possible and will probably never be possible to predict which species are likely to become problem invaders on the basis of traits alone. We therefore suggest that this is one area of invasion biology that merits less attention in the future.”
Invasion biology predicted that lack of genetic variability would hinder evolutionary adaptation in introduced species. This assumption has not been supported by empirical studies: “…rapid evolution has been repeatedly demonstrated in introduced populations, and the predicted reduction in genetic variance has not been observed.”
Rapid evolution of introduced species has been well established by empirical studies: “We have reached the point where additional case studies demonstrating rapid evolutionary change in introduced species are unlikely to have a major impact on our understanding of invasions.” New research questions are needed.
There is little evidence to support the assumption that introduced plant species will cause extinction In native communities: “…there are astonishingly few documented cases of native plants being driven to extinction by competition from introduced plants. There is no evidence for any native species in the United States being driven to extinction even within a state, by competition from an introduced plant species.”

The way forward in invasion biology

Professor Moles and her team then tell us why invasion biology has not been able to prove the assumptions on which the theory is based. The theory of invasion biology was based on untested assumptions that have been accepted as true although there is no empirical evidence to support them. The goal for the future of invasion biology should be to identify these assumptions that have been accepted as dogma, test them, and abandon those that are not consistent with empirical facts.

The authors of this study also, “…join a growing chorus, suggesting that our approach to invasion biology has been too simplistic.” Studies have tended to focus on the features of introduced plants in isolation. A more fruitful line of inquiry will consider the complex interactions between newly introduced species and their new environment:

“Rather than focusing on one factor at a time, we need to find ways (including multivariate analysis) to synthesize information about the recipient habitats/ communities, the characteristics of both resident species and the invaders, demographic processes, propagule pressure [measure of the number of species released into a region in which they are not native], the differences between current conditions and those with which the resident species evolved, evolutionary change to both native and introduced species, plasticity and feedbacks and interactions between different species and processes.”

You might say, “Phew! That sounds like a daunting task.” And so it is, but this team of scientists takes it on with an elaborate and complex study of one of the most basic assumptions of invasion biology: that disturbance facilitates plant invasions.

Does disturbance facilitate plant invasions?

“Disturbance is thought to facilitate invasion by simultaneously opening new ground for colonization, decreasing the competition from resident native species and releasing pulses of resources.” The definition of “disturbance” has varied in different studies, but generally includes fire, grazing, agriculture, erosion, wind, and flood. Empirical tests of this theory have produced mixed results. Even when the results have been positive, they have not persisted over the long-term.

Because disturbance is a natural feature of all ecosystems, native species have adaptive features that enable them to respond to natural disturbances. Therefore, the research team theorized that it is not disturbance per se which creates opportunity for invasions by introduced species, but rather changes in the disturbance regime. Their research study was therefore designed to distinguish between the level of disturbance and changes in the level of disturbance.

Given the international composition of their research team, they were able to select 200 sites in eight countries. They selected only those sites for which the natural patterns of disturbance were known. Their research methods were statistically complex and a detailed description of them is beyond our comprehension and probably many of our readers, but we encourage those with the necessary scientific knowledge to read the article which is available on the internet.

Their analysis of these 200 sites led them to the conclusion that the change in disturbance regimes was far more predictive of the success of invasions than the level of disturbance but that both variables explained only 7% of the variation in the percent of cover or species richness contributed by introduced species.

In other words, one of the most basic assumptions of invasion biology did not pass an empirical test of its validity. Invasions by introduced plants are largely unexplained by disturbance.

New Orleans post Katrina — Post Katrina New Orleans. Floods are another type of disturbance that is likely to increase with climate change.

The future of invasion biology

Science is rapidly revising the assumptions of invasion biology. We strongly believe that it is just a matter of time before science informs us that introduced species are here to stay and that this is not the terrible news we have been led to believe. It is inevitable that this information will filter slowly from the scientific community to the community of native plant advocates. We hope that they hear and accept this good news before our non-native trees are destroyed.

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*Moles, Angela, et. al., “Invasions: The trail behind, the path ahead, and a test of a disturbing idea,” Journal of Ecology, British Ecological Society, 2012, 100, 116-`127. All quotes are from this article

Support for hypotheses in invasion biology is uneven and declining

“Support for major hypotheses in invasion biology is uneven and declining” is the title of a paper recently published in NeoBiota* co-authored by seven scientists from all over the world (Germany, USA, Spain, Canada, Czech Republic). The title captured our attention because it is consistent with our viewpoint.

The international team of scientists analyzed 371 empirical studies which tested six major hypotheses in invasion biology. They found that empirical evidence for these hypotheses is uneven and declining. The hypotheses that were tested by the studies were:

Invasional meltdown: the presence of invasive species facilitates invasion and survival of additional new species.
Novel weapons: invasive species with traits new to an exotic habitat have a competitive advantage over native species.
Enemy release: introduced species have a competitive advantage in the exotic range because they are released from their enemies in the new environment.
Biotic resistance: More biologically diverse ecosystems are more resistant to invasion.
Tens rule: 10% of newly introduced species escape to the wild; 10% of those naturalize in the wild; 10% of those become invasive.
Island susceptibility: Invasive species are more likely to become established and have major ecological impacts on islands than on continents.

The scientists counted the number of studies that support, question/oppose, or are undecided/inconclusive about each hypothesis. They also compared the number of supporting studies when the hypothesis was new with the number of supporting studies published recently to determine the decline in support for the hypothesis. Here’s what they found:

Hypothesis	n	% of supporting studies	% of decline in support
Invasional meltdown	30	77%	41%
Novel weapons	23	74%	25%
Enemy release	106	54%	10%
Biotic resistance	129	29%	5%
Tens rule	74	28%	10%
Island Susceptibility	9	11%	25%

Although support is strongest for the invasional meltdown hypothesis, recent studies are less supportive than early studies, indicating substantial decline in support. Declining evidence of invasional meltdown is consistent with the fact that exotic species are eventually integrated into the food web which reduces their populations, stabilizing their spread. There is apparently little evidence that islands are more susceptible to invasion than continents and few studies have been done to test the hypothesis.

Declining support for scientific hypotheses has been observed in many disciplines, particularly medicine, ecology, and psychology. The scientists who study this phenomenon theorize that the decline is attributable to some combination of these factors:

Over time the amount of available long-term data increases.
The best examples which are the strongest cases for the hypothesis are most likely to be studied first.
Publication bias favors new hypotheses and those for which the results are conclusive.

The NeoBiota paper also observes that the empirical evidence supporting each hypothesis varies by taxonomic group (plants, invertebrates, vertebrates) and habitat type (terrestrial, freshwater, marine). For example:

The novel weapons hypothesis has been tested only for plants in terrestrial habitats.
Support for the invasional meltdown hypothesis is even across taxa and habitats.
Support for biotic resistance is strongest in marine habitats.

Where is invasion biology headed?

The authors of the NeoBiota paper are not suggesting that invasion biology be abandoned. Rather their goal is to redirect scientists in the field to more productive efforts, such as:

Where a hypothesis cannot be generalized to all taxa and habitats specify exactly where it is applicable.
Rather than focusing on newly introduced species, focus on the interaction of a those species with their new environment.
Discard those hypotheses that don’t work.

Based on our fifteen years of experience studying the native plant movement and its theoretical underpinnings in invasion biology we wholeheartedly support the advice of the authors to focus scientific efforts on the interaction of new species with their new environment. We strongly believe that the success of newly introduced species is based largely on changes in the environment into which they are introduced. In other words, invasions are more a result of changes in the environment than on the characteristics of the introduced species.

We also endorse the advice that scientists be more specific about the applicability of the assumptions of invasion biology. We have seen the damage done by sweeping generalizations about how ecosystems operate in the hands of hobbyists. Nature is complex and we do not necessarily understand all the factors operating in a given environment. We hope that scientists will lead the way to the public’s more nuanced understanding of ecosystems.

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*Jeschke, Jonathan, et. al., “Support for major hypotheses in invasion biology is uneven and declining,” NeoBiota, 14: 1-20 (2012)

Hybridization is an adaptive strategy for species survival

Geospiza magnirostris. Linda Hall Library — Large ground finch. Linda Hall Library

We introduced Darwin’s finches to our readers in our previous post. We told you about the research of Rosemary and Peter Grant on the Galápagos Islands that documented the rapid adaptation of the finches to radical changes in their food sources resulting from extreme weather events. In this post we will continue the story by telling you about another of the amazing discoveries of the scientists studying the finches over a period of nearly 30 years.

Natural selection resulted in the survival of finches with body sizes and shapes that were best suited to the availability and type of food. Sexual selection enhanced those physical characteristics during periods in which females had more choice because they were greatly outnumbered by males. In addition to these adaptations, the birds increased their cross-breeding with other species and the resulting hybrids actually had a survival and breeding advantage over their species “pure” parents.*

In the first five years of the research study, there was little evidence of different finch species interbreeding, known as hybridizing. On those rare occasions when species interbred, the resulting generation was not as successful as their parents, with respect to finding a mate and raising another generation.

Such lack of success of hybrids is considered the norm in nature. In fact, many hybrids are sterile, incapable of reproducing. Think of the sure-footed but sterile mule—the offspring of a horse and a donkey—as the classic example of a hybrid.

After the severe drought of 1977 and the flood of 1983, the Grants began to notice an increasing number of cross-breeding birds. It seemed that the resulting hybrids were having more breeding success than the pre-drought hybrids and the data confirmed their observation.

This counter-intuitive conclusion required some careful consideration and the conclusion is a valuable lesson in our rapidly changing environment. The environment on the islands was radically transformed by the severe drought and subsequent flood. The cactus was overwhelmed by a vine that smothered it. The plants with big, hard seeds were attacked by a fungus that decimated the population. The small seeded plants thrived and became the dominant food source.

The rapidly changing environment was causing more rapid evolution and the genetic variability of hybrids was giving them an advantage. If the environment is changing rapidly in unpredictable ways, the birds could increase the odds of finding a winning strategy by increasing the variability of their genes, sometimes resulting in novel traits.

We cannot and should not, however, anthropomorphize the birds by imputing motives to the selection of a mate of another species. The starving cactus finch probably observes that a male of another species—a seed-eating ground finch, for example—appears to be more fit than a male of her own species. She is not thinking of the odds of increasing genetic variability. Natural selection operates without the conscious effort of species.

The implications of hybridization

We are experiencing a period of rapid change because of the anthropogenic (caused by humans) impacts on the environment, most notably climate change, but surely many other impacts which we don’t necessarily understand. These would seem the ideal conditions for the hybridization of species which speeds up evolution by increasing genetic variability.

Unfortunately, one of many strategies of the native plant movement and nativism in the animal kingdom is to prevent hybridization because it is perceived as a threat to native plants and animals. We have reported to our readers some examples of such attempts to prevent hybridization and there are many more in the literature:

Our local native plant society wants only California poppies to be allowed to grow in the exact location in which they historically existed. They fear that if poppies from another neighborhood are allowed to grow in proximity to the local native, “genetic pollution” will occur.

california-poppy — The variety of California poppy being eradicated from the Presidio in San Francisco.

Non-native Spartina marsh grass on the entire West Coast of our country is being eradicated because it was hybridizing with the native species of Spartina.
Conservationists are trying to find American bison that are not hybrids of cattle, with little success. Cattle have been interbreeding with bison for several hundred years, so this seems a fruitless task, like many nativist fantasies.

Are efforts to prevent hybridization depriving plant and animal species of opportunities to adapt to the rapidly changing environment? We don’t know the answer to that question, but we find it a provocative line of inquiry.

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*This information is drawn from: Jonathan Weiner, The Beak of the Finch, Vintage Books, 1994

Darwin’s Finches: An opportunity to observe evolution in action

The finches on the Galápagos Islands are called Darwin’s finches because of the important role they played in the development of his theory of natural selection and evolution of species.

Galapagos Islands - satellite photo — Galapagos Islands, satellite photo. Daphne Major is too small to be visible.

Charles Darwin spent five weeks on the Galápagos Islands in 1835, near the end of a five year expedition. Although he noticed the similarity of the birds on the different islands, he didn’t realize they were all related to one common ancestor until he returned home. Fortunately, he collected many specimens of the birds to bring home for study. It wasn’t until those specimens were examined by an ornithologist that he learned they were 13 species of finches, distinguished primarily by variations in the size of the bird and its beak size and shape.

Unfortunately, he hadn’t recorded which islands the specimens were from, so the implications of their differences were somewhat of a mystery. He lamented in Voyage of the Beagle, “It is the fate of every voyager, when he has just discovered what object in any place is most particularly worthy of his attention, to be hurried from it.”

But Darwin was no dummy, so despite lacking the data necessary to prove his point, he speculated in his memoir, “…in the thirteen species of ground-finches, a nearly perfect gradation may be traced from a beak extraordinarily thick, to one so fine, that it may be compared to that of a warbler. I very much suspect that certain members of the series are confined to different islands…”

Such development of new species from a common ancestor in response to varying environmental conditions is called adaptive radiation. Species also diverge from one another to reduce competition by specializing in a particular food forage type or technique. Nearly 200 years later, science has proven Darwin’s hunch, but just as he had no way of knowing how long this process of speciation took, modern science still cannot answer that question.

Darwin’s finches continue to change in response to changing conditions

Rosemary and Peter Grant have studied the finches on two Galápagos Islands (Daphne Major & Genovesa) for about thirty years. Nearly every year they visited the finches, weighing and measuring every appendage of the birds, especially their beaks. They banded the birds so they could follow their breeding success. They also measured their food: how much food but more importantly how accessible the food is to the birds such as the difficulty of opening seeds.

The availability and type of food is what determines the shape and size of the birds’ beaks. In a year in which there is plenty of rain, there is usually plenty of food which is relatively easy for the birds to eat. When it doesn’t rain, the birds are reduced to the difficult task of trying to crack open a large, hard seed pod. That’s when a big bird with a big beak has an advantage.

Extreme weather is therefore a “selection event,” a time when not every bird is equipped to survive. And the birds that survive are best equipped for those extreme conditions. When the conditions improve, the bird that survived the hard time is not necessarily best equipped for the good times.

These are the principles of natural selection, but they were largely theoretical until the Grants spent many years watching the birds and how they survived such selection events. They had the good fortune to witness two such events in the first twelve years of their study.

The drought

In the fifth year of the Grants’ study, 1977, there was a severe drought. After one short storm in early January, there was no more rain for the remainder of the year. In January, there were 1,300 finches on the island they studied that year. At the end of the year, there were less than 300 finches left on the island.

The Grants measured and weighed the birds that survived the drought. Then they returned to their lab at Princeton University to study their data:

Not a single finch was born and survived on the island in 1977
The surviving birds were 5-6% larger than the dead birds
The average beak size of the birds that survived was 11.07 mm long and 9.96 mm deep. The average beak size of the birds that did not survive was 10.68 mm long and 9.42 mm deep. These critical differences were too small to see with the naked eye, but became evident when the measurements were analyzed by computer. This makes a strong case for scientific measurement verses anecdotal observation, which passes for “evidence” amongst native plant advocates.
Few female birds survived the drought, presumably because male birds are larger than females.

In the years following that drought, sexual selection played an important role in maintaining the population of larger birds with larger beaks. Because the female birds were scarce, they could be very selective in their mates. Who did they choose? Of course, they chose the males with the traits that allowed the birds to survive the drought year. When the ratio of males to females is more even, sexual selection plays a less important role in natural selection in monogamous species such as the finches.

The flood

Here on the West Coast, we are familiar with the weather phenomenon of El Niño, the nickname given to a heavy rain year resulting from an unusually warm ocean current. In 1983, we experienced the strongest El Niño on record, as did the Galápagos Islands.

In 1983, the Grants witnessed the reversal of the results of the 1977 drought: “Natural selection had swung around against the birds from the other side. Big birds with big beaks were dying. Small birds with small beaks were flourishing. Selection has flipped.” *

Lessons learned

Darwin’s finches give us reason for optimism about the future. Nature can and will respond to changes in the environment. Natural selection is not just an historical process that stopped when The Origin of Species was written nearly 200 years ago. Natural selection is operating at all times, whether we notice it or not.

However, the loss of nearly 80% of the birds on a Galápagos Island during a severe drought is not cause for celebration. Although the species survived, hundreds of individual birds did not. So, we are quick to add that our confidence in the adaptive abilities of nature is not an argument for abusing the environment.

Climate change has caused extreme weather events which are undoubtedly selection events for many species of plants and animals. Unless we take action to reduce greenhouse gas emissions we can predict more of such events. Destroying millions of trees solely because they are not native is irresponsible given the contribution their destruction makes to the greenhouse gases causing climate change.

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*Jonathan Weiner, The Beak of the Finch, Vintage Books, 1994

Integrating new species into the food web

We have been reading panic-stricken news reports about zebra mussels for over 10 years, but we weren’t paying much attention until a recent news report that they have arrived in California. We decided it was time to educate ourselves about this “invasive species.”

Zebra mussels and their close relative, the quagga mussel, arrived in the Great Lakes Region of the United States in 1988, probably in the ballast water of big ships. Although they are native to southern Russia and Ukraine, they are now found throughout Europe and England.

The negative side of the ledger

What the mussels lack in size, they make up for in numbers. Though they are tiny—about the size of a dime–they are prolific breeders capable of creating big colonies rapidly. They are a fresh-water mussel which means they exist where there are often water treatment facilities that supply our drinking water. Their larvae are microscopic so they can enter water treatment facilities through the intake pipes and clog the system.

They filter huge quantities of water, consuming plankton (microscopic plants and organisms) depriving other animals of nutrition. This filtering of the water also increases water clarity and light penetration, changing the entire ecosystem in complex and unpredictable ways.

The positive side of the ledger

Where the mussels have gained a foothold, they have quickly entered the food web. A monitoring program was started soon after mussels were found at Long Point Bay in Lake Erie. The first sampling done in 1991 found mussels in 27% of the sampling stations, an estimated 1,189 tons of mussels. By 1992, mussels were found in 80% of the sites, an estimated 4,536 tons of mussels. (1)

In 1992, the monitoring program also started conducting stomach analysis of ducks killed at Long Point Bay. Three species of duck (Greater and Lesser Scaup and Bufflehead) were found to be feeding heavily on the mussels. Between 1993 and 1995 the population of mussels declined significantly from the highpoint of 4,536 tons to only 758 tons in 1995. The population of the duck predators increased correspondingly during the same period of time. (1)

The authors of this study speculate that the mussels were also depleting their food source at the peak of their population and that they had exhausted available attachment sites, but the scientists believe duck predation was the primary reason for the declining population of mussels. As always, there are many variables operating simultaneously in the ecosystem, and it isn’t possible to isolate one from the others. (2)

Ducks aren’t the only predators of the mussels. Crayfish are apparently capable of consuming large quantities of the mussels. And some fish eat the mussels. One study found that yellow perch didn’t eat the mussels in 1994, but a later study in 2004 reported that the perch were eating the mussels. Plankton waste from the mussels settles on the lake bottom and the bottom feeders benefit from that fall out.

There is a downside to this story, however. Remember that the mussels filter the water as they eat. In addition to filtering plankton, they also filter pollutants and contaminants. Researchers assume that the predators of the mussels are consuming those pollutants which then become a part of the food chain. The mussel-consuming ducks at Long Point Bay apparently had elevated levels of contaminants in their tissue compared to ducks that consume only aquatic plants. (2)

What should we do?

According to the news story about the mussels in a local paper, the California legislature is considering increasing the registration fee for boats which would raise about $5 to $8 million dollars. Although the news story isn’t clear about how this money would be used, let’s assume for the sake of argument that it would be used to prevent the spread of these mussels beyond the 25 lakes in California where they are now found. That would apparently involve more inspection of boats being put into the water where the mussels don’t presently exist. If that’s the plan, we enthusiastically endorse it. Prevention is the best medicine, as they say.

But once the mussels have arrived, all scientists agree that eradicating them is not a realistic option. Therefore, dousing them with chemicals—which is one of the recommended treatments—will undoubtedly do more harm than good.

New species quickly become a part of the landscape. Our initial reaction to them tends to be negative because we are suspicious of change. In fact, there may be benefits that aren’t immediately evident and even if there isn’t an immediate benefit, they are often integrated into the environment over time. Their populations often stabilize once they have exhausted available resources. We should be patient because nature is resilient and our time frame is much shorter than nature’s time frame.

Are we learning this lesson?

Broom, Redwood Park, Oakland, California

The California Invasive Plant Council (Cal-IPC) is dedicated to the eradication of non-native plants. Scotch broom is one of their favorite targets for eradication. Little progress has been made in this effort (see “Broom: ‘I’ll be back’” and “Broom: ‘I’m ba-ack’”) and recently Cal-IPC acknowledged this in their newsletter. However, they urged their supporters not to lose heart because they reported that broom is now being browsed by herbivores. So, what native plant advocates could not accomplish with manual labor and chemical warfare, the animals may accomplish by incorporating broom into their diets. One hopes the animals aren’t eating broom doused with herbicides.

Cal-IPC also acknowledges in this article that broom does not grow in shade: “Broom cannot tolerate heavy shade. It usually established following logging or other activities that remove tree canopy.” Could it be that they have finally noticed that the result of clear-cutting non-native trees in the East Bay hills is more broom, not more native plants? We can only hope so.

There are pros and cons to every decision we make. We don’t always know in advance what they are. So, it pays to be cautious. If we are patient, maybe nature will sort it out without our interference. Particularly when our interference damages nature, we should exercise restraint. We should give nature more credit for healing itself. It has a much better track record than we do.

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(1) Cox, George W., Alien Species and Evolution, Island Press, 2004

(2) Petrie, Scott A., Knapton, Richard H., “Rapid Increase and Subsequent Decline of Zebra and Quagga Mussels in Long Point Bay, Lake Erie: Possible Influence of Waterfowl Predation,” J. Great Lakes Research, 25(4) 772-782

Doug Tallamy refutes his own theory without changing his ideology

In our debates with native plant advocates, the scientist who is most often quoted to support their beliefs is Doug Tallamy who wrote an influential book, Bringing Nature Home: How Native Plants Sustain Wildlife in our Gardens. Professor Tallamy is an entomologist at the University of Delaware.

Professor Tallamy’s hypothesis is that native insects require native plants because they have evolved together “over thousands of generations.” Because insects are an essential ingredient in the food web, he speculates that the absence of native plants would ultimately result in “ecological collapse” as other animals in the food web are starved by the loss of insects. (1)

Professor Tallamy freely admits that his theory is based on his anecdotal observations in his own garden, not on scientific evidence: “How do we know the actual extent to which our native insect generalists are eating alien plants? We don’t until we go into the field and see exactly what is eating what. Unfortunately, this important but simple task has been all but ignored so far.” (1)

This research has now been done to Professor Tallamy’s satisfaction by a Master’s Degree student under his direction. The report of that study does not substantiate Professor Tallamy’s belief that insects eat only native plants. In his own words, Professor Tallamy now tells us:

“Erin [Reed] compared the amount of damage sucking and chewing insects made on the ornamental plants at six suburban properties landscaped primarily with species native to the area and six properties landscaped traditionally. After two years of measurements Erin found that only a tiny percentage of leaves were damaged on either set of properties at the end of the season….Erin’s most important result, however, was that there was no statistical difference in the amount of damage on either landscape type.” (2)

Corroborating Evidence

This finding that insects are equally likely to eat native and non-native plants may be new to Professor Tallamy, but it isn’t new to the readers of Million Trees. We have reported many studies which are consistent with this finding.

anise-swallow-tail-butterfly-in-fennel — Anise Swallowtail butterfly in non-native fennel

Professor Arthur Shapiro (UC Davis) reports that 82 of 236 (35%) total species of California butterflies have been observed either laying their eggs or feeding on non-native plants.
Professor Dov Sax (Brown University) compared insects living in the leaf litter of the non-native eucalyptus forest with those living in the native oak-bay woodland in Berkeley, California. He found significantly more species of insects in the leaf litter of the eucalyptus forest in the spring and equal numbers in the fall. Professor Sax also reports the results of many similar studies all over the world that reach the same conclusion.
The California Academy of Sciences finds that several years after planting its roof with native plants, it is now dominated by non-native species of plants in the two quadrants that are not being weeded, replanted and reseeded with natives. Their monitoring project recently reported that there were an equal number of insects found in the quadrants dominated by native plants and those dominated by non-native plants. (Correction: Should read “…equal number of orders of insects…”)
Jennifer Owens (Ph.D., University of Michigan) reports 30 years of observing her garden in Wildlife of a Garden (Royal Horticultural Society, 2011). She found that non-native species were better as food plants for moth larvae than native species. Moth larvae used 27% of the native species in the garden as food plants, and 35% of the alien plants.

English garden Great Dixter — The English garden, where plants from all over the world are welcome

Specialists vs. Generalists

When debating with native plant advocates, one quickly learns that the debate isn’t ended by putting facts such as these on the table. In this case, the comeback is, “The insects using non-native plants are generalists. Insects that are specialists will not make that transition.” Generalists are insects that eat a wide variety of plants, while specialists are limited to only one plant or plants in the same family which are chemically similar.

Professor Tallamy offers in support of this contention that only “…about 10 percent of the insect herbivores in a given ecosystem [are not specialists],” implying that few insects are capable of making a transition to another host plant.

However, categorizing insects as specialists or generalists is not a dichotomy. At one extreme, there are some insects that choose a single species of plant as its host or its meal. At the other extreme, there are insects that feed on more than three different plant families. It is only that extreme category which has been estimated at only 10% of all phytophagous (plant-eating) insects. The majority of insects are in the middle of the continuum. They are generally confined to a single plant family in which the plants are chemically similar.

Putting that definition of “specialist” as confined to one plant family into perspective, let us consider the size of plant families. For example, there are 20,000 plant members of the Asteraceae family, including the native sagebrush (Artemisia) and the non-native African daisy. In other words, the insect that confines its diet to one family of plants is not very specialized.

Soapberry bug on balloon vine. Scott Carroll, UC Davis — Soapberry bug on balloon vine. Scott Carroll. UC Davis

Professor Tallamy offers his readers an explanation for why specialist insects cannot make the transition from native to non-native plants. He claims that many non-native plants are chemically unique and therefore insects are unable to adapt to them. He offers examples of non-native plants and trees which “are not related to any lineage of plants in North America.” One of his examples is the goldenrain tree (Koelreuteria paniculata). This is the member of the soapberry (Sapindaceae) family to which the soapberry bug has made a transition from a native plant in the soapberry family in less than 100 generations over a period of 20 to 50 years. Professor Tallamy’s other examples of unique non-native plant species are also members of large plant families which probably contain native members. Professor Tallamy is apparently mistaken in his assumption that most or all non-native plants are unique, with no native relatives.

The pace of evolution

Even if insects are “specialists” we should not assume that their dependence on a native plant is incapable of changing over time. Professor Tallamy’s hypothesis about the mutually exclusive relationships between native animals and native plants is based on an outdated notion of the slow pace of evolution. The assumption amongst native plant advocates is that these relationships are nearly immutable.

In fact, evolution continues today and is sometimes even visible within the lifetime of observers. Professor Tallamy provides his readers with examples of non-native insects that made quick transitions to native plants:

The hemlock wooly adelgids from Asia have had a devastating effect on native hemlock forests in the eastern United States.
The Japanese beetle introduced to the United States is now eating the foliage of over 400 plants (according to Professor Tallamy), some of which are native (according to the USDA invasive species website).

These insects apparently made transitions to chemically similar native plants without evolutionary adaptation. If non-native insects quickly adapt to new hosts, doesn’t it seem likely that native insects are capable of doing the same? That is both logical and consistent with our experience. For example, the native soapberry bug mentioned above has undergone rapid evolution of its beak length to adapt to a new host.

Although Professor Tallamy tells us that the relationship between insects and plants evolved over “thousands of generations,” he acknowledges much faster changes in plants when he explains why non-native plants become invasive decades after their arrival: “Japanese honeysuckle, for example, was planted as an ornamental for 80 years before it escaped cultivation. No one is sure why this lag time occurs. Perhaps during the lag period, the plant is changing genetically through natural selection to better fit its new environment.” Does it make sense that the evolution of plants would be much more rapid than the evolution of insects? Since the lifetime of most insects is not substantially longer than the lifetime of most plants, we don’t see the logic in this assumption.

Beliefs die hard

Although Professor Tallamy now concedes that there is no evidence that insects are dependent upon native plants, he continues to believe that the absence of native plants will cause “ecological collapse.” In the same book in which he reports the study of his graduate student, Professor Tallamy repeats his mantra: “…our wholesale replacement of native plant communities with disparate collections of plants from other parts of the world is pushing our local animals to the brink of extinction—and the ecosystems that sustain human societies to the edge of collapse.”

This alarmist conclusion is offered without providing examples of any animals being “pushed to the brink of extinction.” In fact, available scientific evidence contradicts this alarmist conclusion. (3)

Here are more articles about the mistaken theories of Doug Tallamy:

Doug Tallamy claims that non-native plants are “ecological traps for birds.” HERE is an article that disputes that theory.
Doug Tallamy claims that native and non-native plants in the same genus are not equally useful to wildlife, but he is wrong about that. Story is HERE.
Doug Tallamy advocates for the eradication of butterfly bush (Buddleia) because it is not native. He claims it is not useful to butterflies, but he is wrong about that. Story is HERE.
Doug Tallamy publishes a laboratory study that he believes contradicts field studies, but he is wrong about that. Story is HERE.
Doug Tallamy speaks to Smithsonian Magazine, Art Shapiro responds, Million Trees fills in the gaps: HERE
Doug Tallamy’s Nature’s Best Hope perpetuates the myth that berry-producing non-native plants must be eradicated because they are less nutritious than the berries of native plants. Available HERE.
Doug Tallamy believes we must prevent hybridization. Hybridization is a natural process that increases biodiversity and enables plants and animals to adapt to changes in the environment. Available HERE.
There is NO evidence to support Doug Tallamy’s claim that insect populations are declining because of the existence of non-native plants. Available HERE.

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(1) Tallamy, Doug, Bringing Nature Home, Timber Press, 2007

(2) Tallamy, Doug, “Flipping the Paradigm: Landscapes that Welcome Wildlife,” chapter in Christopher, Thomas, The New American Landscape, Timber Press, 2011

(3) Erle C. Ellis, et. al., “All Is Not Loss: Plant Biodiversity in the Anthropocene,” http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0030535

Biological Control: Another dangerous method of eradicating non-native species

We were recently reminded of the use of biological controls to eradicate non-native species when we learned that Australian insects may have been illegally imported to California to kill eucalyptus, which had been virtually pest free until 1983. So, an article in the New York Times about the development of a fungus for the purpose of killing cheatgrass (Bromus tectorum) caught our attention. The fungus has been given the ominous name, Black Fingers of Death, for the black stubs of cheatgrass infected with the fungus.

Cheatgrass is one of the non-native grasses that have essentially replaced native grasses throughout the United States. It was probably introduced with ship ballast and wheat seed stock in about 1850. As we have reported, native grasses were quickly replaced by the non-native grasses which tolerate the heavy grazing of domesticated animals brought by settlers. Native Americans had no domesticated animals.

Biological controls have frequently caused more serious damage than the problems they were intended to solve. Therefore, we would hope that their intended target is doing more damage than the potential damage of its biological control. We must ask if the cure is worse than the disease. And in this case, we don’t think the damage done by cheatgrass justifies inflicting it with the Black Fingers of Death.

The track record of biological control

Biological control is the intentional introduction of animals, pests, microbes, fungi, pathogens, etc., for the purpose of killing a plant or animal which is perceived to be causing a problem. The ways in which some of these biocontrols have gone badly wrong are as varied and as many as the methods used.

Introduced species of plants are said to have an initial advantage in their new home because their pests and competitors are not always introduced with them. This is the “enemy release hypothesis” popular amongst native plant advocates to explain the tendency of non-native plants to be invasive. However, this is usually a temporary advantage which is exaggerated by native plant advocates who do not seem to recognize the speed with which native species can adapt to new species, and vice versa.

Therefore, a popular method of biological control is to import the predator or competitor of the non-native species which is considered invasive. This is only effective if the pest is selective in its host. There are many examples of such introductions which did not prove to be selective: “For the United States mainland, Hawaii, and the Caribbean region, Pemberton (2000) listed 15 species of herbivorous biocontrol insects that have extended their feeding habits to 41 species of native plants…” (1) Although most of the unintended hosts were related to the intended hosts, some were not.

Similar shifts from target to nontarget species have occurred for biocontrol agents of animal pests: “For parasitoids introduced to North America for control of insect pests Hawkins and Marino (1997) found that 51 (16.7%) of the 313 introduced species were recorded from nontarget hosts. For Hawaii, 37 (32.3%) of 115 parasitoid species were noted to use nontarget hosts…biological control introductions are considered to be responsible for extinctions of at least 15 native moth species [in Hawaii].” (1)

There are also several cases of biological controls escaping from the laboratory setting before they had been adequately tested and approved for release. A virus escaped the laboratory in Australia and killed 90% of the rabbits in its initial spread through the wild population. Very quickly, the virus evolved to a less fatal strain that killed less than 50% of the rabbits it infected. A second virus was then tested and also escaped its laboratory trial and has spread through the rabbit population throughout Australia.

A fly being considered for introduction to control yellow starthistle apparently escaped and damaged a major cash crop of safflower in California according to a study published in 2001, illustrating the risks of biocontrols to agriculture.

This is but a brief description of the diverse ways in which nature has foiled the best efforts of the scientists designing biological controls for non-native species of plants and animals. The source of this information (1) therefore concludes, “…many releases of species have inadequate justification…The first goal of research must be to show that the introduced biological control agent will not itself cause damage.” Given this wise advice, we will return to the question, “What damage is being done by cheatgrass and does that damage justify the introduction of The Black Fingers of Death?”

Why is cheatgrass considered a problem?

Cheatgrass is one of the many non-native annual grasses which have replaced the native grasses which were not adapted to the grazing of domesticated animals. Cheatgrass is a valuable nutritional source for grazing animals when it is green and loses much of its nutritional value when it dries.

Grazing is only one of the types of disturbance which create opportunities for non-native grasses to expand their range into unoccupied ground. Fire is another disturbance which gives cheatgrass a competitive advantage over native grasses because it uses available moisture and germinates before native grasses can gain a foothold on the bare ground cleared by fire.

Cheatgrass is said to increase fire frequency by increasing fuel load and continuity. Unfortunately, increasing levels of CO₂ (carbon dioxide) in the atmosphere is increasing the fuel load of cheatgrass: “…the indigestible portion of aboveground plant material [of cheatgrass] …increased with increasing CO₂.” (2)

Carbon dioxide is the predominant greenhouse gas which is contributing to climate change. And increasing frequency of wildfires is one of the consequences of the higher temperatures associated with climate change. Therefore, one of the causes of the expanding range of cheatgrass is increasing levels of the greenhouse gases contributing to climate change. Rather than address the underlying cause, we are apparently planning to poison the cheatgrass with a deadly fungus.

If we are successful in killing the cheatgrass, what will occupy the bare ground? Will native grasses and shrubs return? Will whatever occupies the bare ground be an improvement over the cheatgrass which has some nutritional value to grazing animals? The US Forest Service plant database gives us this warning, “Care must be taken with methods employed to control cheatgrass so that any void left by cheatgrass removal is not filled with another nonnative invasive species that may be even less desirable.”

Recapitulating familiar themes

The project to develop a deadly fungus to kill cheatgrass is another example of the issues that we often discuss on Million Trees:

Are the risks of the methods used to eradicate non-native species being adequately assessed and evaluated before projects are undertaken?
Are the underlying conditions—such as climate change–that have contributed to an “invasion” being addressed by the methods used to eradicate them? If not, will the effort be successful?
Is the damage done by the “invasion” greater than the damage done by the methods used to eradicate the invader? Is the cure worse than the disease?

We do not believe that these questions are being addressed by the many “restoration” projects we see in the San Francisco Bay Area. Consequently, we believe that these projects often do more harm than good.

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(1) Cox, George W., Alien Species and Evolution, Island Press, 2004

(2) Ziska, L.H.; Reeves III, J.B.; Blank, R.R. (2005), “The impact of recent increases in atmospheric CO₂ on biomass production and vegetative retention of cheatgrass (B. tectorum): Implications for fire disturbance.”, Global Change Biology. 11 (8): 1325–1332,

The futility of eradicating non-native species

We tend to focus on the native plant “restorations” in our neighborhood, but we should not lose track of the fact that similar efforts are taking place all over the world. The native plant movement is international and if it loses momentum, we should expect to see loss of support for its destructive projects elsewhere. So, today we will tell our readers about several recent developments that suggest that scientists all over the world are having second thoughts about invasion biology, which is the scientific underpinning of the native plant movement.

Second Thoughts: The Hawaiian Case

We have reported to our readers about the many “restoration” projects in Hawaii. There is some logic to focusing such efforts on islands, because they are the places most vulnerable to the loss of native species attributed to introduced species and theoretically they are also the places where re-invasion should be easiest to control.

Scientists have recently published the results of a ten-year effort to return an “invaded” forest to its native origins. They spent about 5 years clearing the forest of all non-natives. They planted the scorched earth with natives and then they walked away from it to observe the long-term sustainability of their effort. Five years later they report that the composition of the forest—with respect to its nativity—has essentially returned to its original state.

They tested several hypotheses while observing the changes in the forest during the second half of the project. Conventional wisdom had been that the more densely natives occupied the ground, the less vulnerable it would be to re-invasion. Much to their surprise, this was not the outcome of their experiment. The more densely natives occupied the ground, the greater the population of non-natives in the final analysis. They conclude that the same conditions which encouraged the growth of native plants were equally beneficial to the growth of non-native plants.

This study was conducted by the US Forest Service. We hope they learned something from this experience. Specifically, we hope that the US Forest Service now understands that native plant “restorations” are not a one-shot deal. They are a permanent commitment to garden that restoration with the same amount of effort. That’s why scientists—such as Professors Arthur Shapiro and Peter Del Tredici—tell us that large scale projects are not sustainable in the long term. A small scale native plant garden as an historical illustration is a worthwhile effort. Gardening our vast public lands is like “plowing the sea,” as Professor Shapiro told us recently.

Second Thoughts: The New Zealand Case

New Zealand has made herculean efforts to save its native species from “invasions” by non-native species: “New Zealand is a very weedy country. Indigenous plant species are matched in number by naturalized exotic species and about 20 new invaders are discovered each year. Thus, a weed eradication program has been under way for the past 10 years, but eradicating an unwanted plant species is much more difficult than it might seem.” (1)

Eradicating yellow tree lupin in New Zealand, NZ Dept of Conservation — Eradicating yellow tree lupin, New Zealand Dept of Conservation

How successful have these efforts been? According to a recent study, they have had very little success: “The current issue of the journal Invasive Plant Science and Management assesses the progress of 111 weed eradication programs carried out by New Zealand’s Department of Conservation. Only four of these programs have met with success, while 21 have been discontinued and the rest remain an ongoing challenge.”

The report concludes, “After a decade, New Zealand’s weed eradication strategy has yet to yield significant results.” Anyone who has been watching similar efforts all over the San Francisco Bay Area will not be the least bit surprised by this conclusion. With the exception of small gardens which are irrigated and intensively gardened, these projects are weedy messes, usually behind fences.

Second Thoughts: The Australian Case

Emma Marris interviewed the manager of one of many “restoration” projects in Australia for her book, Rambunctious Garden. He told her about the 18 month process of killing all non-native animals in a 15-square mile sanctuary enclosed by a prison-like fence, “sturdy, tall, and electrified.” (This was half of the Scotia Sanctuary)

“He was able to shoot out the goats in a matter of days. Rabbits were harder…he put out carrot bait…the rabbits…would learn to trust the new food source…[then] the carrots would be poisoned…[He] repeated this routine three times, running through 12,500 pounds of carrots…For each fox, he learned its habits and was eventually able to find perfect places to trap or poison them. He also trapped cats…The key to making it work, he says, was ‘perseverance, perseverance, perseverance.’” (2)

It was necessary to kill all the non-native animals before taking on the more difficult task of returning the land to native plants because of the interaction between the plants and animals. The non-native animals are considered a continuing and permanent threat to the sanctuary. The expectation is that this 250 acre restoration will require human intervention indefinitely into the future.

Australia is a huge place, so the prospect of this labor-intensive process being replicated on a nationwide basis is absurd. Therefore, it seems inevitable that Australian scientists would begin to question the efficacy of such efforts.

Just two months ago, an Australian scientist, Angela Moles, gave a TED (Technology, Entertainment, and Design) presentation suggesting that it is time to grant Australian citizenship to introduced species. Click here to see the video.

Her reasoning is based on the relatively new understanding of the speed with which evolution occurs. Her laboratory used the collection of a university herbarium to measure the changes in the plants that were introduced to Australia. The herbarium had samples of the same species of plants collected over a 60 year period from the same location. They found that the plants had changed in significant ways. In a sense, they were becoming Australian plants in response to the biotic (other plants and animals) and abiotic (climate, soil, etc) conditions of their new home. She predicted that if they weren’t yet genetically distinct from their ancestors, they soon would be. In other words, they are becoming distinct, new species…..Australian species.

She showed a slide of her son who is a 2^nd generation Australian. He is considered an Australian by law and custom. Then she showed a slide of clover which has changed significantly since its introduction. After 130 generations, it is still not considered Australian. After showing a few of the massive eradication projects and describing the scale and futility of those efforts, she suggested that it is long past time to accept the clover and other introduced species as Australian.

And, of course, we agree. Let us abandon the destructive and futile war on non-native species. The sooner we do, the less damage will be done to the environment and to the animals that live in it, including us.

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(1) “Eradicating Weed Species in New Zealand Poses a Larger Challenge Than Expected,” Science Daily, July 21, 2012

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

The “Look, don’t touch” approach to environmental education

Environmental education plays an important role in the native plant movement. Young people are indoctrinated with the native plant ideology and recruited as volunteers in native plant restorations.

We were introduced to the relationship between environmental education and the native plant movement on our first visit to the Randall Museum in San Francisco. The Randall is operated by San Francisco’s Recreation and Park Department. According to its website it “…offers youth and adults opportunities for active involvement and recreation in an integrated program of arts and sciences…The Museum strives to inspire creativity, curiosity, and appreciation of the world around us.”

On our first visit, the main room of the museum was decorated with posters that had been drawn by the children visiting the museum. The posters covered the perimeter of the room. Each poster featured an animal, a plant, and the message “Save California’s native plants for the [pictured animal].”

Snowy Plover poster2 — Poster at the Randall Museum

The relationship between each animal and the pictured native plant seemed tenuous at best. Here is a picture of one of those posters, which claims that the Snowy Plover requires a particular native plant. In fact, Snowy Plovers make no use of this plant or any other.

According to The Sibley Guide to Bird Life and Behavior, “Plovers…are specialized feeders that rely on vision to locate their prey, which includes all manner of invertebrates such as earthworms, adult and larval insects, amphipods, isopods, tiny crabs…” etc. They don’t eat plants nor do they require plants—let alone native plants—for nesting because they nest on the bare sand.

In addition to being misinformation, this approach to environmental education struck us as rather sterile. It reminded us of a public hearing about San Francisco’s Natural Areas Program at which a native plant advocate explained her objective for the education of children in San Francisco. She said that children should be required to memorize the names of 30 native plants each day. How boring, we thought. Would children be inspired to love nature by such a rote exercise?

Separating children from nature

Billy Goat Hill - SNRAMP sign3 — “Stay on designated trails” Signage in San Francisco’s “natural areas”

We are apparently not the only ones who have reacted to such an uninspiring approach to environmental education. In a recent article in Orion Magazine (1), a parent tells the story of taking his children to a class at the Happy Hills Nature Center. The nature center is surrounded by a meadow blooming with wildflowers, but instead of wandering through that meadow to explore, the children are required to go inside on a sunny day and watch 27 slides of wildflowers. They are bored stiff. When the class is over, they want to get outside, but they are told to stay on the trail and not to pick the flowers, even the non-native dandelions.

This is typical of the experiences that children are now getting in our parks. They are prohibited from wading in the creek or lake. They are prohibited from climbing the rocks or trees. Fences and signs require that they stay on the trails. They are told that nature is fragile and will not tolerate their presence. They are effectively prevented from interacting with nature. They may look, but they may not touch.

The Orion article concludes that this approach to environmental education will not foster an interest in or respect for nature. If children are alienated from nature, they will not have an interest in protecting it. The article cites two research studies in which early experiences with nature are found to correlate with an interest in nature as adults.

One study surveyed environmentalists to determine if there were any similarities in their childhood experiences. It found that “Most environmentalists attributed their commitment to a combination of two factors, ‘many hours spent outdoors in a keenly remembered wild or semi-wild place in childhood or adolescence, and an adult who taught respect for nature.’”

Another study interviewed two thousand adults in a wide range of occupations chosen at random in one hundred urban areas around the country. They found that “Childhood participation in ‘wild’ nature such as hiking or playing in the woods, camping and hunting or fishing, as well as participation in ‘domesticated’ nature such as picking flowers or produce, planting trees or seeds, and caring for plants in childhood have a positive relationship to adult environmental values.”

Of course, we couldn’t help but think of our own early experiences with nature. Vivid memories of building forts in the trees and dams in the creek came to mind. Both activities would be prohibited in today’s parks.

Defeating the purpose of environmental education

Memorizing lists of plants or looking at slides of them in a darkened room is not a substitute for interacting with nature. And that interaction will not take place behind a fence. The result of such childhood experience will be adults who are not interested in nature and therefore don’t care about protecting it. Ironically, those who claim to be devoted to saving nature are defeating their purpose by separating children from nature.

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(1) David Sobel, “Look, Don’t Touch,” Orion Magazine, July/August 2012