An Australian friend of eucalyptus

An Australian sheep farmer (we would say “rancher”), Jane Pye, spotted our defense of eucalyptus and got in touch:

“G’day, I stumbled across the SFFA website researching ‘allelopathy’ in eucalypts and was amazed to find so much antipathy towards gum trees over there – like an arboreal cane toad! What I really wanted to know is do you have any evidence of ‘positive allelopathy’ re eucalypts?  I live in the Australian outback with areas of dry sclerophyll forest. The commonest eucalypt here (Eucalyptus populnea) is often surrounded by native scrub trees & bushes. Strangely some of these box trees also have other trees growing out of their trunks which I think were planted there by the traditional owners (Aboriginal). These Tree in Trees are found in clusters around the old indigenous campsites, which are in turn found around good natural water catchments or native wells.”

My article debunking the popular myth that eucalyptus is allelopathic was republished by the San Francisco Forest Alliance (SFFA).  The myth of allelopathy is that eucalyptus emits a chemical that prevents the germination of other species, eliminating competition with eucalyptus for resources such as water.  But Jane’s experience with eucalyptus goes beyond debunking allelopathy in eucalyptus.  She has documented many examples of different tree species that have seemingly been planted inside the cavities of eucalyptus trees.  The eucalypts are a sheltering host to the guest tree species.  Clearly, eucalyptus is not inhospitable to other plant species.

Wilga (Geijera parviflora) guest in Bimblebox (Eucalyptus populnea) host.
Apophyllum anomalum guest growing from Bimblebox (Eucalyptus populnea) host

Jane believes that these “trees in trees” were intentionally planted by indigenous Aboriginal “farmers.”  She believes that this is one of many techniques that were developed by Aboriginal people to manage the land and vegetation to provide food and cultural implements.  She explains on her website:

“After years of admiring and speculating about these scar trees, I have finally gotten around to photographing most of them. I spend many days in the paddocks mustering sheep and some of these trees are like old friends. They are an important link to our Aboriginal past and a reflection on how innovative and resilient these people were. Surviving out here west of Walgett with our unpredictable climate of harsh droughts and random floods is still tough but these people managed their environment and thrived.

“So I dedicate this website to Freddie Walford, an Aboriginal stockman we had who taught us some bush lore and like many of his people, died too young. I will always remember his natural affinity with livestock, his love of polocrosse and his quiet humour and grace. He never spoke much about the scar trees but did say if I was ever to see bones inside an old coolabah [Eucalyptus coolabah], I should go as fast as possible in the opposite direction! This website aims to increase knowledge and record these trees but not to display any pictures or information that is culturally secret or sacred.”

Australian aborigines. Photo by Thomas Dick, 1920

The land management practices of Australian Aborigines were very similar to those of indigenous Californians for much the same reason.  These were hunter-gatherer cultures living in similar climates with seasonal drought.  They moved around as seasons changed and their diets changed accordingly.  Both cultures used fire as one of their primary tools.  Periodic fires refreshed the grasses that fed the grazing animals they hunted.  The primary grazers in Australia were kangaroos and other marsupials; deer and other ungulates are the original grazers in California.

Native Americans setting grass fire, painting by Frederic Remington, 1908

The land management practices of indigenous people are enjoying a renaissance.  A recent study of Aboriginal land management in Australia said, “Indigenous agency and governance is driving innovations in land management worldwide that provide more equitable solutions and strategic approaches to looking after the lands, waters and all living things, particularly in the face of climate change.”

Such intentional burns are now seen as a way to keep the brushy fuels that carry fire to a minimum, reducing wildfire hazards.  Cal Fire’s new “Wildfire and Forest Resilience Plan” and the Governor’s recent annual budget proposal tell us that more prescribed burns are planned in California to reduce fuel loads and fire hazards:  “CAL FIRE will expand its fuels reduction and prescribed fire programs to treat up to 100,000 acres by 2025, and the California Department of Parks and Recreation and other state agencies will also increase the use of prescribed fire on high risk state lands.”

It has taken hundreds of years to appreciate the value of indigenous land management and its context in their culture.  When Europeans arrived in both America and Australia, settlers assumed that their culture was superior to indigenous culture.  Early settlers made no attempt to learn from indigenous people, which was the settler’s loss.  Indigenous people had learned to live off the land, in most cases without cultivating crops and without domesticated animals.  Rather, indigenous people learned what was edible and what had medicinal value.  The first European settlement in America, Jamestown, ended quickly with starvation, because the settlers weren’t able to understand what the land offered them.  In Australia, knowledge of indigenous land management was also delayed by the cultural taboos of the indigenous people that prohibited the revelation of many of their cultural practices outside their ancestral clans.

 Wildfire in Australia

Jane also had some interesting observations about wildfires in Australia that are consistent with our experience in California:

I’m sorry to hear eucalypt forests are being destroyed over there as they are wonderfully useful trees. We don’t have many fires in inland Australia. It’s more of a coastal / high rainfall problem. We just don’t get the fuel build up as it’s a semi-arid region and we have thousands of merino sheep eating the grass and shrubs. There have been no fires on this property in over a century and probably much longer. We also have efficient native grazers – kangaroos and wallabies and now also goats that are increasingly common as an alternative to sheep.”

Jane Pye’s home. Gingie Station, Walgett, NSW, Australia. There are many places in California’s Central Valley that look much the same.

This is the strategy that I promote on this website.  If we reduce ground fuels that ignite easily, we can prevent most fires from igniting tree canopies that are harder to ignite.  Fire travels fast on the ground if given a continuous field of dry grass during the dry season.  Grazing animals are a far safer way of reducing these grassy ground fuels than the herbicides that are often used.  Herbicides leave a dead, dry thatch on the ground that is very flammable and grazing does not.

Walgett, Australia. Average Hi Temp 80 degrees. Average Lo Temp 54 degrees. Average rainfall 19 inches.

“Also we are very used to fire over here and many people regard those foolish enough to build in fire prone areas have only themselves to blame. Some of our small coastal towns are totally surrounded by National park and State forest and only have one road in – that’s why there were so many images of people sheltering on beaches last summer. It’s a hard issue but better hazard reduction burns and more fire fighting aircraft seem to be the way forward here. Also better fire retardant building materials.”

These observations are also consistent with the strategy that makes sense to me.  We must learn to live with fire because it is an essential element in Mediterranean ecosystems.  We can’t prevent it, but we can work around it with zoning that prevents building in extremely hazardous areas, using fire retardant building materials, and creating safe evacuation routes.

Thanks, mate!

 Alerted by Jane, I noticed this woody shrub sprouting from a eucalyptus stump in Stern Grove a few days after I heard from Jane.  Clearly, eucalyptus does not retard the growth of other species.

Stern Grove, San Francisco

Many thanks to Jane for getting in touch with us.  Thanks for her admiration of eucalyptus and Aboriginal culture.  I’ve had some lovely email chats with Jane.  Perhaps you would like to drop her a line to thank her as well:

Where does it end?

It is our pleasure to republish with permission a post from the website of Flood Creek Non-Nativist Landcare Group.  Flood Creek is located in Braidwood, New South Wales, Australia.  Across Australia, Landcare is a popular volunteer-based environmental movement which enjoys general support from government in the form of occasional financial grants. Over the last 25 years, many Landcare groups have undertaken projects with the stated goal of eradicating non-native plants based on a belief that native plants and animals would benefit.  That strategy will sound familiar to our readers, as will the damage to the environment which it causes.  

The Non-Nativist Landcare Group is a small team of people with a history of participation in Landcare who want to foster a discussion of current nativist approaches to environmental management, and question their outcomes.  Based on their experiences with conventional Landcare projects, the Non-Nativist Landcare Group has concluded that these often do more harm than good.  The Group describes their mission:   “Above all, this discussion is inspired by the goal of taking a more ecologically-based and functional approach to Australian socio-ecological systems and their health. We seek to highlight the inconvenient-truth that rational environmental management can never be based upon a simple mantra of “natives good, non-natives bad”. Extermination is rarely an effective way to promote landscape diversity and resilience.”

Please visit their website and wish them well in their effort to find a less destructive approach to land management.

When you look at the willful and wanton environmental destruction conveyed in these photographs you must ask yourself: ‘how could anyone do this in the name of environmentalism?’ After all the disturbance we’ve already inflicted upon this biosphere, how is this really helping?

Flood Creek 1


In this example of willow demolition, the trees were cut down and dragged away and the stumps were poisoned. Then (for some unfathomable reason) a drainage ditch was excavated into the floodplain. In the photo below, the main flow-line is 40m off to the left.

Flood Creek 2

Apart from the economic motives at play (a theme for a future post), I can think of only one reason why an ‘environmentalist’ might condone this kind of damage and disturbance. It must be to do with that old adage, ‘the end justifies the means‘.

The reasoning seems to be: ‘Sure, it makes a big mess and causes erosion, and nutrient release, and carbon emissions, and local temperature increases, and loss of habitat, but it’s necessary because we’re going to make Australia a place for natives-only again.’

So that’s the end we’re aiming for: a ‘native-only’ Australia. And these photos show the means we must accept along the way.  It seems we’re just going to remove all of the non-natives from this continent so the environment is back to ‘pristine’ again and then we can stop with the chainsaws and excavators and herbicides in the name of ‘saving’ the environment.

Flood Creek 3

We just want 1788-Australia back. Presumably without the dingoes and without the previous intrinsic Aboriginal management; plus with a few minor additions like cattle; and sheep; and horses; and apples; and asparagus; and hops; and wheat; and rice; and trout; and tomatoes; and lettuce; and cats; and dogs; and goldfish; and maybe just one or two other things, but that’s it! And we want all the ‘invasive’ natives, like Cootamundra Wattle, and Sweet Pittosporum, and Kookaburras to know their place and to go back where they were when Europeans first arrived….And stay there forever and ever….And not move just because the climate or fire regime has changed. And this won’t happen by itself so we’ll need funding and legislation and heavy machinery. And we’re going to fix it all ‘real good’ without knowing what it was actually like or exactly what species existed in many parts of the country back in 1788. And….and…..

Flood Creek 4

….And then again……When you think about it…..Are we ever actually going to achieve anything even remotely approaching a native Australia?…..really?

I doubt it.

And I’d doubt the sincerity (or sanity) of anyone who says that we could. Surely nobody actually believes this?

So, given this impossibility, it seems pretty reasonable to ask ourselves: ‘how can the end justify the means, when it’s clear there really is no conceivable end?’ If it just goes on and on forever, then how do we justify these means to no end at all? How do we live with this permanent state of expensive self-congratulatory environmental vandalism?

More importantly, given how well-supported the above activities currently are, how do objecting grassroots Landcarers begin to articulate new ways to work with the adaptive living-landscapes around us? And how do we influence the direction of our own movement so that participation in Landcare is not assumed to mean support for this destruction?

All the death and destruction in these photographs is familiar to us here in the San Francisco Bay Area.  The only difference is that the trees that were destroyed in this project were willows, which are native in California, but not native in Australia.  That difference helps us appreciate the arbitrariness of nativism, which treats eucalyptus as demons and willows as the “good” trees in California.  

We have yet to witness a “restoration” that wasn’t far more destructive than constructive.  And based on our experience in the San Francisco Bay Area, we can venture an answer to the rhetorical question, “Where does it end?”  It doesn’t end because every “restoration” is quickly occupied again by the plants that were destroyed by herbicide applications.  As long as the objective continues to be to kill everything non-native and re-populate a landscape with native plants, the project will never be complete. 

 Therefore, it only ends when the goal is revised and/or the effort is no longer funded.  And the only way to achieve that revised goal is for the public to object to the destruction of their public lands.  So, if you are tired of witnessing these destructive projects, speak up!  Tell your elected representatives that you don’t want your tax dollars spent on the pointless ruin of public open space. 

Californian-Australian Exchange

With a little help from our friends, we have discovered a new resource to help us understand why Blue Gum eucalyptus was brought to California from Australia.  True Gardens of the Gods:  Californian-Australian Environmental Reform 1860-1920 was written by an Australian historian, Ian Tyrrell.  Although we have read other accounts of the introduction of eucalyptus to California (most recently Jared Farmer’s Trees in Paradise), the perspective of an Australian on this history was new to us.

Those who despise eucalyptus often portray its introduction to California as a horrible mistake to be regretted and reversed.  Ian Tyrrell helps us to understand that there are actually good reasons for the introduction of eucalyptus that make sense in the context of the geographic and cultural realities of the historical period in which it was introduced. 

Historical geography of eucalyptus introduction

The gold rush in California and Australia occurred nearly simultaneously in 1849.  As these gold rushes played out, there was considerable travel of hopeful miners and their support structures between the two continents.  Naturally, they brought things with them that they considered useful to their enterprises and seeds of the Blue Gum were amongst their baggage from Australia to California.  Although there is speculation about the precise time and means of initial introduction, they remain theories.

Presently we think of Australia as being far away because our primary means of transportation is air travel and that trip is much longer than the trip to the East Coast of the US.  However, at the time of the gold rush, travel by ship was the primary means of transportation and the trip to Australia by ship was much shorter than the trip to our East Coast.  The trip around the horn of South America was both long and extremely dangerous.  In Richard Henry Dana’s Two Years Before the Mast, we share his terror during that voyage in the 1830s.

Hydraulic gold mining in California.
Hydraulic gold mining in California.

This shared experience of a gold rush meant that California and Australia also shared the environmental damage caused by the methods used to extract gold from the land.  Hydraulic mining was the primary method of extraction.  This method uses high-powered water pumps to erode riparian corridors to expose the gold in the soil.  Erosion is the result of this method of mining.

Ian Tyrrell tells us that the initial motivation for planting eucalyptus in California was to heal environmental damage caused by the gold rush.  Eucalyptus was an attractive choice for this task because it grows quickly and is well adapted to California which shares the same Mediterranean climate as much of Australia.  It seems ironic that the initial motivation for planting eucalyptus in California was to repair environmental damage, given that today the same trees are blamed for environmental damage by native plant advocates and mainstream environmental organizations such as the Sierra Club.

Our East Coast remained inaccessible to California until the completion of the transcontinental railroad in 1869.  The Panama Canal (completed in 1914) accommodated movement of large shipments of goods between the West and East coasts.

The cultural context

Tyrrell also introduces us to the intellectuals on both continents who were the environmentalists of the era of the gold rush.  George Perkins Marsh in America and Baron Ferdinand von Mueller in Australia were the environmental leaders of that period.  They were both committed to introducing species to their respective countries to improve the environment by creating “gardens of the gods”:  “These were pragmatic thinkers who leaned toward afforestation rather than preservation when the opportunity presented itself.  Early conservationists were, at bottom, advocates of a constructed landscape that would improve nature, not preserve.  In short, they were advocates for the garden concept.”   (1)

Mount Davidson, San Francisco, 1885.
Mount Davidson, San Francisco, 1885.

In California, the desire to import tree species from outside California was supported by the fact that much of California is naturally treeless.  Many species of trees that are native to California are not well adapted to many microclimates.  For example, if you want trees on a windward facing hill along the coast of California, you must plant a non-native.  So, cultural preference for introduced trees was supported by horticultural requirements of native tree species.

Timber famine

A second phase of afforestation with eucalyptus occurred towards the end of the 19th century when there was widespread fear in America that we had severely depleted our timber resources and would soon experience a shortage of timber needed to build our new communities.  Eucalyptus was considered an attractive substitute for native timber sources because it grew quickly.  Plantations of eucalyptus were planted throughout California based on the belief that a valuable market for the timber was just around the corner.

This period of speculative investment in eucalyptus came to an abrupt end around 1914 for several reasons:

  • Young eucalyptus does not make suitable lumber for building purposes.  We have since learned that eucalyptus makes valuable lumber at about 80 years of age.  We have also perfected kiln-drying techniques that produce high-quality eucalyptus lumber.
  • The economic value of eucalyptus forest for timber was also reduced because of the limited ability of eucalyptus to regenerate naturally:  “The eucalyptus bore ‘seeds abundantly, but apparently the latter does not find, as a rule, the proper conditions for germination…Except with the aid of the hand of man, therefore, the eucalyptus will not sensibly encroach upon the treeless area’” (1)  (This is yet more evidence that eucalyptus is NOT invasive, as native plant advocates claim.)
  • The demand for timber declined precipitously when alternative building materials were developed such as iron and cement.

Australia on the receiving end

Australian eucalyptus forest (Eucalyptus regnans). Victoria, Australia
Australian eucalyptus forest (Eucalyptus regnans). Victoria, Australia

As eucalyptus was introduced to California, Australians were importing the Monterey pine for timber.  Monterey pine is planted all over the world for timber.  It is the predominant timber species in New Zealand, but it never became as popular in Australia because it is softwood.  Eucalyptus is a hardwood and Australian’s developed a preference for hardwood that could not be satisfied with Monterey pine.  Unfortunately, that preference for hardwood has decimated the old-growth eucalyptus forests of Australia.

There is a lesson in this for us.  One of the advantages of introducing non-native trees is to protect native forests.  If we use our non-native trees to fulfill practical needs such as lumber and firewood, we are taking the pressure off the need to destroy our native forests.  Eucalyptus is still planted in many developing countries where firewood is still needed for fuel.  Wouldn’t we rather that these countries burn fast-growing eucalyptus than their native forests?

What can we learn from the Californian-Australian exchange?

Environmentalism is a cultural construct.  Its meaning has changed and will undoubtedly continue to change because culture is dynamic, just as nature is dynamic.  Mid-Nineteenth Century environmentalism was not wedded to native species, as is contemporary environmentalism.  Fifty years ago, when Rachel Carson’s Silent Spring was published, pesticide use was considered harmful to the environment.  Now we find that mainstream environmental organizations are actively promoting the use of pesticides to support their demands for eradication of non-native plants and trees.

We tend to look back at historical ways of doing things—such as planting eucalyptus—with a condescending attitude: “How could they be so stupid?”  Another way to look at the past is to look at the historical context in which those choices were made.  If we had sufficient knowledge of the historical context, perhaps those choices would make good sense.

Finally, if we look around the world at what is being planted today, we must acknowledge that planting non-native tree species often has practical advantages.  Non-native tree species might grow where native species won’t grow and where we need trees for windbreaks, visual and sound screens, erosion and pollution control, carbon sequestration, etc.  Or non-native tree species might protect native species by fulfilling specific needs that would otherwise require the use of native species.

As we often do on Million Trees, we reach the conclusion that more knowledge often results in more tolerance.  Thanks to Ian Tyrrell for these insights and to our friends for alerting us to this valuable resource.

(1) Ian Tyrrell, True Gardens of the Gods:  Californian-Australian Environmental Reform, 1860-1930, University of California Press, 1999

The New Nature: Winners and losers in wild Australia

In The New Nature, Australian ecologist Tim Low takes us on a tour of his continent/country to make the point that every nook and cranny has been impacted by the activities of humans.  (1) It is a dizzying adventure because it challenges many of our assumptions about nature:

  • Human civilization has benefited many plant and animal species in Australia.  For example, places such as garbage dumps and sewage treatment plants are sources of food for many species, from the bottom of the food web to the top.  Many animals hang out in the company of humans where they find housing, food, and protection from their predators.
  • However, there are “winners” and “losers” in the changed environment.  Not all species benefit equally from the resources provided by humans and not all species are equally adaptable to change.
  • When “winners” dominate at the expense of rare species, the “winners” are nearly always native species, according to Low.  Non-native “invaders” are hardly mentioned in Low’s tour of Australia.
  • Low defines “conservation” as active management of ecosystems, including aggressive culling (AKA killing) of native species as needed to prevent extinction of rare species.  He acknowledges that these massive killings are controversial in Australia, which was some comfort to us.
  • Eucalyptus forests in Australia are in serious trouble.  There is no evidence in Australia that they are the aggressive “invaders” they are labeled in California.
The Australian eucalyptus forest as painted by Hans Heysen:  Mystic Morn, 1904
The Australian eucalyptus forest as painted by Hans Heysen: Mystic Morn, 1904

As ecologists tend to do in the United States, Low uses pre-European Australia as the baseline from which changes in ecosystems are judged.  The Aborigines of Australia were hunter/gatherers, like many Native American tribes in North America.    Like our Native Americans, they used fire to support their hunting.  Periodic burning of grassland promotes the growth of new grass which attracts the grazing animals they hunted.  In Australia, the grazing animals were marsupials, such as kangaroos, rather than the ungulates in North America.  Periodic burning also prevented natural succession from grassland to forests.

When Europeans arrived, the population of Aborigines plummeted as it did in North America and the remaining population was displaced from most of their homelands.  Their way of life was radically altered and hunting was no longer their primary means of living.  That was the end of the annual grassland fires that had maintained the grassland.

Australian eucalyptus forest as painted by Frederick McCubbin:  The Pioneer, 1904
Australian eucalyptus forest as painted by Frederick McCubbin: The Pioneer, 1904

The Europeans brought sheep and cattle that partially replaced the function of the Aboriginal fires to maintain grassland.   However, there is a fine line between over-grazing and grassland maintenance.  Many native grasses were replaced by annual grasses introduced with the livestock of the Europeans, just as it was in North America.  Europeans in Australia actively suppressed fire for safety reasons.

Here is a brief summary of the consequences of these changes in human use of the land:

  • Koala and joey.  Creative Commons
    Koala and joey. Creative Commons

    There were few koala bears in Australia when Europeans arrived at the end of the 18th century.  They were easy marks for Aboriginal hunters because they sleep in the canopy of trees during the day.  When Aboriginal hunting stopped, the population of koalas skyrocketed.  Because they are so cute, humans love them and they want them everywhere, so they have been introduced into parks where they had not lived in the past.  Now they are killing eucalyptus forests in those parks.  Park managers want to cull them and sometimes they do, but Australians strenuously object to these efforts to balance the population of koalas with available resources.  When managers are prevented from culling, the forests die and the koalas eventually starve.  This makes for disturbing reading.

  • Kangaroos in native grassland
    Kangaroos in native grassland

    Kangaroo populations have benefited from both the disappearance of Aboriginal hunters and the eradication of dingoes by cattle and sheep ranchers.  The large species of kangaroos now have no natural predators so their populations have destroyed much of the grassland that they graze.  Kangaroos are also aggressively culled and Australians aren’t happy about that either.

  • Insect predators of eucalyptus forests have increased because they are “fed” by the fertilizer in stock paddocks.
  • The absence of fire has also radically altered many ecosystems.  Where kangaroos and stock have overgrazed, the fires that start aren’t sustained because there isn’t sufficient fuel.  When there are no fires to reduce the understory, the forest retains more moisture.  The forest gradually converts from dry forests to tropical forests and the trees cannot regenerate in the wet, dense understory:  “If you take eucalypt forest, add fertilizer and water, you have the recipe for rainforest.”   This is another factor in the decline of the eucalyptus forest in Australia.
  • The changes in these ecosystems reverberate throughout the food web.  The insects, birds, and animals that lived in one type of ecosystem aren’t necessarily adapted to the changes.  Some species disappear and others arrive that often compete with their predecessors in the ecosystem, further diminishing rare species.

Although there are North American counterparts to most of these changes in the environment, the concluding chapters of Low’s remarkable book are entirely foreign to us.  He is unequivocal in his assessment that human attempts to compensate for the damage that has been done to Australian ecosystems in their residential gardens inflicts even greater damage by helping “winners” displace “losers.”  Bird boxes and feeders benefit only the most aggressive birds which give them an even greater advantage over the forest birds that are in decline.  Likewise, garden ponds are occupied by only a few species of the toughest frogs.   His assessment of native plant gardening is so surprising that we will quote it directly:

One tenet of wildlife-friendly gardening is that native plants be used, but often that’s not what animals want.  Growing native plumbago for native butterflies doesn’t help as much as growing the exotic equivalent, which sprouts hundreds more flowers.  And switching native animals over to native plants is often harder than it sounds.”

We visited Australia as tourists for a month, but that is nearly the limit of our understanding of its ecology.  It felt much like home inasmuch as it’s another of the five Mediterranean climates in the world.  We can’t claim that this experience is sufficient to question Tim Low’s description of Australian ecology.  So, until we learn otherwise, we must say that the drivers of environmental change in Australia are primarily anthropogenic and the existence of non-native species plays little role.  However, we can’t help but wonder if a difference of perception accounts for the radically different assessment of American ecologists.  In other words, are American ecologists blaming non-native species for environmental changes that are just the consequence of human activities?   That seems another equally logical explanation for the radical difference in American and Australian assessments of non-native species.


(1)    Tim Low, The New Nature:  Winners and Losers in Wild Australia, Penguin Books Australia, 2002

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, 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

Scotia Sanctuary, Australia

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 2nd 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.  


(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