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April 04, 2005

On invasions and exotics and natives

Hungry Hyaena draws attention to a post by Swarthmore history professor Timothy Burke on the issue of invasive species and our attitudes toward them. Though Burke's post is about six months old, it contains some statements that I think bear continued comment.

Burke tells of a trip to the Canadian Rockies in which he found poor fishing in some streams, due in part to a Parks Canada policy against stocking fish. From Burke's post:

The purpose behind Parks Canada policy appears to be two-fold. First, to remove trout from aquatic environments within the National Parks where non-native predatory fish are deemed destructive in their impact on the ecosystem; second, to protect native species like the bull trout and the cutthroat trout.

The first objective I can see—it’s easy to forget that the introduction or repeated re-stocking of trout into waters that wouldn’t normally support a trout population has a significant impact on other organisms, like amphibians, particularly if the water is cold enough for the trout to reproduce.

The second objective I feel a bit more ambivalent about. If rainbow trout elbow out bull trout, then that’s a problem from the standpoint of losing a species of trout, but on the other hand, rainbows pretty well occupy the same niche as bull trout, only more successfully and possibly voraciously. The vision here isn’t just the preservation of a species — it’s the larger antipathy towards “invasive species” that’s become an orthodoxy of environmental science.

The statement that rainbows are appropriate replacements for bull trout in Alberta trout streams is trivially easy to debunk, so let's save it and deal with that last, rather inflammatory statement first.

There's a nascent if not growing tendency on the part of non-scientific observers of the sciences to speak in terms of "orthodoxy," or "dogma," to portray scientists as members of a bureaucratic herd who are largely opposed to independent thought.

You see this most often, of course, among creationists who oppose the teaching of evolution in the schools (or anywhere else for that matter), but it also comes to the surface in cases like the recent debacle over the unfortunate Terry Schiavo, in which people who couldn't diagnose a fractured femur on an x-ray declared that the panel of neurologists who declared Schiavo's persistent vegetative state were acting out of some sort of obligatory pro-death sensibility. In my line of work, I hear such statements coming from the environmentally concerned, most often when they criticize researchers for failing to support notions like Multiple Chemical Sensitivity or health hazards from EMFs, or when they defend homeopathy and other pseudosciences.

One can easily write off such people as "kooks," but Burke is no kook. Tim Burke is a friend of the sciences and a thoughtful and careful writer, so that fact that this notion appears in his writing is worth study.

And, as it turns out, Burke is using the phrase "orthodoxy" in a context that gives many friends of the sciences similar misgivings. He continues:

I do wonder about that attitude a bit, not just in the context of fishing, but as a whole. When I read some of the material on the dangers of invasive species, its rhetoric and tropes sometimes seem uncannily familiar, reminding me very much of ideas about race, miscegenation and nativism in modern colonialism, in post-colonial nationalism, and in identity politics.

This is, of course, not a new idea, as almost anyone who has worked to restore native plants to a patch of land will tell you. Many people react near-violently to the thought of removing even the most invasive and destructive plants from a piece of landscape: broom in the California coast, feijoas in Hawai'i and Florida. In Virginia, I even heard strong argument for allowing kudzu to grow unimpeded.

We who have torn out invasive plants to plant local natives have been called Nazis, compared to Serbian "ethnic cleansers," accused of racism and genocide. And that response pales by comparison to that received by those who suggest housecats might not be the best addition to wild landscapes.

This response is not limited to the grassroots, but is occasionally echoed in statements by the mainstream media and representatives of local government. In San Francisco, for example, defenders of native species have come under sustained attack on three fronts. There are the feral cats, which especially in Golden Gate Park have wiped out most of the ground-dwelling birds, including native quail. In the Presidio, there are attempts to cut down invasive eucalyptus tress - which far from being passive catchers of wind and rain, have been implicated in the direct killing of native bird species due to sticky nectar that seals hummingbirds' nostrils - in favor of plantings of endangered species once native to the site. And there are the plovers, endangered beach-nesting birds that are particularly vulnerable to disruption by free-roaming dogs, and in whose interest the National Park Service is attempting to enforce a leash law on a section of Ocean Beach. All three issues have earned defenders of native species regular and scientifically illiterate criticism from San Francisco Chronicle columnist Ken Garcia and County Supervisor Leland Yee.

If the charge of hewing to orthodoxy is to be made, it's as defensible to level it at opponents of efforts to control exotic species as it is to criticize environmental scientists for it.

And though the notion of a scientific herd mentality is not wholly without merit, science at its best carries the seeds of self-correction. It's worth noting that a century ago, the scientific community was more or less persuaded that introducing exotic species into ecosystems was a value-neutral event, if not actually a beneficial action for the ecosystem as a whole. It was agricultural scientists who introduced kudzu to the southeast, for instance, choosing it for the very characteristics of fast growth and hardiness that make it anathema today.

In fact, Burke's very language underlines the fact that ecological science has shifted away from a previous consensus in favor of introductions, where he mentions that Parks Canada has stopped stocking non-native fish. Which means that at one point Parks Canada did stock exotic fish, presumably on the advice and with the consultation of the best wildlife biologists to which Government Canada had access.

All this raises the question: why has the science shifted so radically in a relatively short period? Answer: because we have learned about the damage such introductions can cause.

When you use words such as "orthodoxy," the clear connotation is of inflexibility, of hewing to a dogma despite evidence to the contrary. What scientists concerned about invasive species display may, in some cases, be unwarranted concern. It is far from being orthodoxy.

That's a lot of analysis of one word in Burke's piece, but it's a pivotal word. I by no means intend this allusion as a slight to Burke, but his argument is remarkably like that Michelle Malkin used recently in condemning the recent salad-dressing attack on Pat Buchanan. Malkin decried the attack, and rightly so, but then went on to allege that this violence was the exclusive province of the left, ignoring that fact that violence from the right is higher by several orders of magnitude. Similarly, Burke ascribes "orthodoxy" to scientists and others concerned about invasive species, while giving a free pass to those who would impose the jargon and definitions of wholly unrelated social sciences onto the discipline of wildlife biology.

That's not to say that native species defenders haven't been flagrantly insensitive to the connotations of the loaded language they often use carelessly to describe invasive species. I've met a few California native plant activists who regard Central American laborers in much the same way they do invasive star thistle. This is problem enough that I've written on the subject, as for example in this piece, which when it was first published in the Contra Costa Times won me a fair bit of hate mail from the racists at

Executive summary of the piece: Not all exotic species are invasive. Origin of the species isn't the issue; behavior is. And though the language some use to describe invasive species is redolent with horrible memory, that doesn't mean we ought to fall into the trap of metaphor. People coming from other places increase diversity, while invasive species decrease it.

As illustration of the warning against conflating "invasive" and "exotic," a mistake that many die-hard native plant activists make staggeringly often, consider the raven. The raven is native to the Mojave Desert. The raven is an invasive species in the Mojave Desert. Ecosystem disruption and human presence have encouraged an increase in raven numbers in the desert, and this increase comes at a catastrophic cost: the seemingly inevitable extinction of the desert tortoise, whose young are a favorite raven snack.

It's behavior, not origin, that concerns wildlife biologists.

Burke continues:

There’s some similar desires to stop the forward motion of change, to fix environments (human or natural) in their tracks, the same suspicion of dynamism.

This is definitely true among some sectors of the environmental movement. It's largely untrue among wildlife biologists - especially in the arid Western states, where change is stochastic rather than continuous - and almost completely untrue among paleobiologists and paleontologists, whose work is based almost entirely on recording and analyzing evidence of past ecosystems radically different from those in which we now live.

Popular understanding of the environmental sciences seems to lag a generation or more behind the actual state of the science. A lay environmentalist may believe that preserving an ecosystem at status quo, in situ, in perpetuity is a laudable goal. A freshman undergraduate student in the environmental sciences knows this is an impossibility. Not only do species migrate and their populations fluctuate, but the species themselves change, through speciation, genetic drift or depauperation, random acts of carnage, and the occasional natural advent of new species into their habitat. Extinction is a normal process taking place at a background level that may occasionally spike, due either to disaster or to the vagaries of chance.

Dynamism is the normal state of affairs in an ecosystem, which after all functions to disperse and use up solar energy as completely and efficiently as possible. The question, as Timothy himself readily admits, is scale. How much additional strain does the current rate of destructive species introductions add to an ecosystem burdened with damage from human society? And how much does the damage from human society accentuate the success of invasive species - many of which are disturbed ecosystem colonizers?

Resume fisking:

What is particularly striking to me is that the arguments against “invasive species” even from scientists sometimes seem not so much technical or scientific (when they are, they usually rest on the relatively weak assertion that there is a burning necessity for general biodiversity that trumps all other possible principles of ecological stewardship) but mostly aesthetic.

This is the key point in Burke's essay, and the key controversy in the whole range of subjects relating to environmental protection. That "relatively weak assertion" about biodiversity is the foundation of the ecological sciences. Because one of the outmoded metaphors long ago abandoned by scientists but still revered by lay enthusiasts is "the balance of nature," there seems to be a general sense that a few judicious extinctions are no real problem. If the bull trout goes extinct, at least there's a rainbow trout of about the same size to "keep the balance," as if we were replacing one literal fish with another on a literal balance scale.

But the "balance of nature" - as I've written before - is misconception based on a tautology. A complex system is beset by disruptive events generated from within and without, internal instabilities, long-term and erratic fluctuations, and other forms of unanticipated and largely unquantifiable change. The notion of the "balance of nature" stems from the fact that the complex ecological systems we live in wander over time into what seem to us to be stable states. And since "stable" is defined as "lasting a long time," these states by definition characterize a significant part of the system's timeline. Nature no more "seeks balance" than a slinky seeks the stair tread on which it happens to stop.

Instead, the characteristic tendency of the living world is one of reacting to disruption. Intertidal organisms react to - and have in many cases evolved dependency on - the twice-daily flooding of their habitat with salt water and desiccating air. An old tree falls and another, spurred to growth by the new bright light penetrating the canopy, grows to take its place. Plants in the coastal California landscape push new shoots through incinerated soil after a fire, their seeds or roots having weathered the conflagration.

We need not resort to thought experiment to see that species diversity in an ecosystem is often directly proportional to the facility with which that ecosystem adapts to disruption. Bulldoze an acre in Pennsylvania, one in western Kansas, and one in the Mojave, and see ten years later which site has the most obvious damage still remaining. There's a degree to which this risks a "correlation is causation" argument; you could argue that the Mojave's aridity causes both the low biodiversity and slow rate of "recovery." So do a second experiment. Bulldoze four acres: one in the woods on the ridge outside Williamsport PA and one in central Philadelphia; one in the wild margins of the Antelope Valley and one in Lancaster, CA, a few miles down the road. Barring other influences, the tracts with neighboring wild biodiversity will "heal" faster.

That land's "healing" does not mean "regaining its previous state." Each blading and regrowing of that Pennsylvania forest will result in a different patch of woods, with different species concentration in both plants and animals. Colonization of disturbed habitat does not proceed on a fixed schedule, but rather varies with absolute random chance: is the first plant to colonize a dandelion or a patch of timothy? Do the crows move in, or the blue jays?

And yes, this defense of the value of biodiversity can be boiled down to "biodiversity is good at ensuring continued biodiversity." Burke's point about the value of biodiversity being essentially an esthetic one has some merit. Similarly, it is difficult to discuss the state of global human rights without a shared assumption that wantonly and callously causing unnecessary pain to other people is to be avoided, though there is no real hard-science reason to avoid torture. Most people presume that democracies are better than dictatorships, though there are plenty of rational arguments that dictatorships are more efficient. To some extent, Burke is correct: valuing biodiversity is an esthetic choice.

But there are marked utilitarian arguments as well. For example: with pesticides, habitat disruption, destruction of food plants, and introduction of competitors, we've killed off a huge proportion of the native pollinating insects in the US. We've been able to weather this severe depletion of biodiversity due to our importation of efficient, tractable Eurasian honeybees. But honeybees have one life strategy: large colonies. Their lifestyle makes them vulnerable to brood parasites such as the varroa mite, to which native pollinators such as solitary bees, who do not maintain hives, are resistant.

Varroa mites are currently marching through the honeybee populations of North America. So are tracheal mites, which are pretty much what they sound like. Though innovative control measures are being used, there is some question as to whether we can assume the continued existence of honeybees for many more decades.

Oh, and if the honeybees go, so do four-fifths of our food crops.

We rely for our very lives on the intricate interplay of the global ecosystem, containing perhaps a hundred million species. We exist by consuming a portion of that ecosystem. The stability of that ecosystem is a benefit to us. Biodiversity functions as a set of redundant systems to ensure ecosystem function: If one pollinator fails in the course of a year or a decade, others can fill in for it. And - as any crop-diversified farmer will tell you - biodiversity in and of itself helps prevent certain kinds of ecosystem failures.

Burke continues:

I readily agree that an introduced species which might appear harmless or inoffensive can have unpredictable effects on an ecosystem. It’s a classic source of emergent change. But what’s interesting to me is that the strongest general attacks on all invasive species frequently concede that it’s impossible in general to predict the full long-term consequences of a species introduction, and indeed in many ways impossible to predict or manage the long-term arc of change in any ecosystem even assuming that all introductions of new species could be prevented. I wonder then why there is such certainty, therefore, about the horror of any and all species introductions.

I would be interested to see some of these attacks on introductions of "all" new species. Even in New Zealand, the most invasives-conscious nation on the planet (it's socially acceptable there to shoot kitty cats, for crying out loud) furor over introductions is limited to species shown to have been invasive in other locations, or their close relatives. (Which, by the way, counters the "impossible to tell" argument. You can't anticipate every problem, but you can make some pretty damned accurate educated guesses.)

There simply is no group of people advocating a ban on imports of all species not native to, or established in, their region. If this were proposed, the howls of the nursery industry would be heard as far as Alpha Centauri. Not even the Kiwis are talking about banning tulips, or maize, or daffodils.

In fact, the social momentum is heading the other way. Between 90 and 99 percent of the biomass in San Francisco Bay is made up of invasive species, but the EPA is still trying to evade its legal responsibility to ban dumping of ballast water under the Clean Water Act. Free trade agreements ensure that potentially disastrously destructive wood-boring insects enter the US each year in wood pallets of sweatshop clothing and video came cartridges.

At most, what environmentalists and environmental scientists propose in the US is not a ban, but merely actions to stop the worst introductions from being carried out inadvertently, and for deliberate introductions (such as of beneficial insects) to be done with some forethought given to the effects and the social benefit - which benefit is hopefully more than a few hours of distraction for anglers.

And we're losing.

I wonder then for the same reason whether it is really so terrible if rainbow trout displace bull trout in waters that support trout populations. There are consequences to that—loss of genetic resources of the bull trout population, possibly pressure on prey populations due to the more voracious appetites of the rainbow trout, and loss of the unique “character” that bull trout provide, whatever that might be...

A place to start looking is in the very success of the rainbow trout. If the rainbows are faring better than the bulls, it may be due to resistance to a disease that kept bull trout numbers in check, or ability to take advantage of a helpful resource that was inaccessible to the bulls. That success relative to the native trout means that the stream will have more trout in it in the short term, and despite the biases of anglers, this is not necessarily the best thing for the stream ecosystem as a whole. What of the effect mentioned above on prey populations? When those are depleted, what of the effects on less-preferred prey? If the trout population crashes as a result of the rainbows eating themselves out of house and home, what becomes of the animals that rely on a steady supply of fish?

but the intrinsic, instinctive horror at the idea of a “native” species displaced by a very similar “non-native” one seems to me to come largely from the same place that modern ideas about race, identity and nationality in human beings have come from, somewhere deep in the cultural and ideological foundations of modernity and not from a cleanly rational scientific principle. There's a rich potential intellectual history lurking in there somewhere--in fact, I strongly suspect that it's already been written, and I'm simply not aware of it.

Though some misguided enthusiasts, as I've mentioned, do resort to sloppy metaphor - perhaps as a sign of their own xenophobia - this sentiment is pretty much limited to the fringes.

There is, however, a wonderful existing work on invasive species ecology that draws parallels with the regrettable human history of the last millennium, and I think Burke would find it valuable - though the ideas it proposes are 180 degrees counter to the ones Burke offers in his piece. The book is Ecological Imperialism; The Biological Expansion of Europe, 900-1900 by Alfred Crosby.

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Wow. A little light reading before bed. Unfortunately (or maybe not) time constraints and a newborn will keep my comments to a minimum.

First, from a longtime professional angler. Comparing bull trout and rainbow trout is dicey, at best. The two species frequently occupy complimentary niches in the same ecosystems and their relationship is as much beneficial to each species as it is adversarial. Perhaps more so. A reasonably good analogy would be mountain lions and mule deer.

Next, the introduction of hatchery fish, which was glossed over, is the piscatorial equivalent of bio-engineered corn. Only in this case, the bio-engineering was done without much of a plan, or any consideration for the eventual consequences.

For what it’s worth, I guess my broader view on aliens and exotics is that we’re messing with Pandora’s Box. In the vast majority of cases, we’re taking a functional ecosystem and introducing problems. For example, the New Zealand mud snails in Lake Ontario are removing so much plankton from the lake that indigenous minnows, who feed on that same plankton, are experiencing population crashes. Which, in turn, affects everything that depends on those minnows for food. (Although scuba divers like the snails, because the water is far clearer than it was just ten years ago.)

Finally, an interesting (and perhaps appropriate) anecdote. A few years ago, the state of Idaho floated the idea of poisoning all the rainbow trout in a large stretch of the upper Henry’s Fork river, perhaps the most famous trout fishery in the world. After the rainbows were gone, Idaho Fish & Game wanted to restock the river with cutthroat trout, the river’s original inhabitants, who had been out-competed over the years by stocked, and subsequently wild, rainbows. Depending on where their priorities lay, various anglers came out either for or against the plan. A friend of mine, who happens to be of Native American origin, offered what I thought was the most appropriate response. “I’m all for getting rid of the exotics,” he told me, “as long as we don’t stop with the trout.”

Posted by: tost at April 4, 2005 10:27 PM
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This is a really interesting and thought-provoking piece -- very much worth the links to it. If I were still teaching, I'd have my students come by and read it; there'd be a lot for us to mull over later.

Posted by: Rana at April 5, 2005 10:06 AM
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Nice piece!

One thing I ended up following up on at my blog was that it turns out bull trout and rainbow trout get along fine, as tost notes: the real issue is actually brook trout and bull trout, who compete in spawning sites. Also it turns out bull trout are actually char, which complicates things slightly.

Also Parks Canada's stocking history around Banff is actually very complex. At least some of the rainbow population that is famously vigorous south of Calgary was established by an accidental stocking--a stocking truck that was heading for an artificial lake near Banff broke down and they offloaded the fish into the river. Or so I was told when I got into a long conversation with a park officer about the issue.

I'm not sure I want to back off the invocation of "orthodoxy" here, as if the use of "loaded language" is just a kind of minor rhetorical error. I don't think it's that easy, and it's why I mention the really complex tropes and discourses that ride along when you use words like "invader" or "alien" to describe introduced species. I think those words do organize a paradigm, not just or even primarily a scientific one but a paradigm for policy and practice.

PZ Myers and I talked about this a while back in a different context. State policies that are informed by scientific research are not the same thing as science, but neither are they wholly separable. Scientific research programs often continue to govern policy far past the date of their own expiration within pure research communities, and I think this is especially true for ecological and environmental policy. I think you really can talk about orthodoxies, because once science is used to craft policy, then those policies create stakeholders, people who benefit from them (as well as people who lose because of them). The defense of those policies invokes science, and scientists are often in very real ways clients or obligated to policymakers, who dispense monies for research. It would be very hard, I think, to get Parks Canada or a similar agency to disperse money to underwrite a sustained research project that was agnostic about or critical of the concept of "invasive species", for one example. The dance here is complicated: research that gets done without these entanglements often ends up moving policy, but with a very substantial lag time.

I'm curious about whether you've seen this month's issue of -Discover- Magazine. It has a long article on the concept of "invasive species", and features a number of ecologists who pretty much echo my argument that the concept of "invasive species" has become something of an orthodoxy, with all that implies.

Posted by: Timothy Burkr at April 5, 2005 01:43 PM
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I'm not sure I want to back off the invocation of "orthodoxy" here, as if the use of "loaded language" is just a kind of minor rhetorical error. I don't think it's that easy, and it's why I mention the really complex tropes and discourses that ride along when you use words like "invader" or "alien" to describe introduced species.

Well, that's not a bad point. And the fact that I argued against what seemed to me (in your admittedly short piece) what seemed an unnecessary blanket criticism shouldn't be taken as disagreement with your sense that the parallels are important. I had to leave one otherwise useful native plant email list in disgust over the blatant racism of one rather prominent native plant enthusiast, so I've got some of that all-important anecdotal evidence to support your argument.

In fact, if it wasn't for the importance of that trope, I wouldn't have written the piece I linked to in the body of this post!

I'm just looking forward to a discussion that takes things to the next level, I suppose. Yeah, there's a commonality between worrying about invaders in wildlife form and worrying about "invaders" in human form. But there's also a way in which objecting to the use of the word "invasive" to describe Caulerpa on social offensiveness grounds accepts - if only for rhetorical purposes - the assumption that the "invader" humans aren't exactly human.

Posted by: Chris Clarke at April 5, 2005 02:01 PM
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Timothy - Brook trout are also char, although I'm not aware of any original overlap between the two species - brookies being an east coast fish, and bull trout existing on the other side of the continent.

I had an interesting electronic conversation a couple years ago with Ted Williams, who writes for Mother Jones and Fly Rod & Reel, among other publications. We were discussing Montana FW&P's decision to poison the brookies and rainbows from a small creek on Ted Turner's ranch near Bozeman. Williams felt the state response was appropriate - he'd happily sacrifice a few thousand non-native fish in an isolated stream in order to restore a native, and declining, sub-species of cutthroat. While I felt the goal was praiseworthy, killing every fish in a stream in order to start with a blank slate doesn't sit well with my moral compass. I'm still not sure how you reconcile the two.

And charged language, of course - invasive, alien, etc. - can, and does, raise the temperature of the conversation. At the same time, there are situations where a spirited exchange of ideas is beneficial, and this may well be one of those instances.

Chris - A favor, as I'm feeling a little slow today. (Not much sleep for the last few weeks.) Would you explain that last sentence in your comment? I don't know why, but I'm not following you. Thanks.

Posted by: tost at April 5, 2005 06:05 PM
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Sure, tost.

Equating "invader species" with "invaders" from a human culture is a statement that the invader humans aren't the same species as the humans in situ.

You see this in the parallel some draw between native species defenders and xenophobes - sometimes correctly, as I've mentioned - and you also see it in the trope I often hear in California: "well, I'm not a native species, so why should my shrubs have to be native?" Well, ma'am, unless you think the Miwok and Mojave are a different species than you are, you are a native species.

Hey, tost, how is that little exotic invader that's depriving you of sleep? Well, I trust.

Posted by: Chris Clarke at April 5, 2005 06:17 PM
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Thanks, Chris. That sounds about right, and I tend to agree with you. (Although I could make a reasonably good argument that behavior is almost as accurate an indicator of species as biology. In which case your clueless shrub owner is about as far from native as you can get.)

A case in point. Last summer, a friend and I were driving north on a deserted road in south-central British Columbia. Off in the distance, on the far side of the road, we saw a coyote. As we approached, the coyote slowed down from a trot and then stopped. When I pulled up, he walked out into the middle of the road and stopped about 8 feet from my driver's side door. I rolled down the window and talked to him. He looked up at me, and at my buddy, and grinned. When I heard a logging truck in the distance, I pulled off to the shoulder. Then my buddy jumped out to shoo the coyote off the road - in my experience, loggers don't have much sympathy for the wildlife they run over.

Long story short, for the next twenty minutes that coyote played with my friend. Picked up his hat and ran off with it. Danced with him. Came up and touched my friend's leg, grabbed his pants in his teeth - but playfully, sort of a "Come one, let's have some fun." type of tug.

So how do we explain this type of activity? Was it in fact a coyote? All I can say is that I'm extremely familiar with coyotes, and this creature looked exactly like a coyote. It was also the largest, most perfect example of the species I've seen in the west. And it wasn't in, or near, a protected park. Nor did it seem sick or senile. In fact, it looked like Central Casting had just washed and blown dry this gorgeous wild creature. Amazingly, after two weeks of solid rain, there wasn't even any mud on the hair around his toes.

And how can I explain the fact that this coyote freaked out and ran off every time another car or a truck came down the road - something that happened 3 or 4 times over the course of the 20 minutes - but that he was just fine with my friend and I? In fact, he came back every time to hang out with us, and to play.

Anyway, using behavior as a criteria, this coyote was no more a coyote than your gal with her shrubs is a human. Something to think about.

As for Kian - I've been sick and he's caught my cold. Which sucks, as babies can't breath through their mouths, and his nose is all stuffed up. Other than that, though, we're all beginning to think that this grand experiment might actually work out OK. What's really great is that I continue to expand my capacity for love - something I wouldn't have guessed was possible. I am truly blessed, and incredibly thankful, for a life I probably don't deserve.

Posted by: tost at April 5, 2005 06:57 PM
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Chris, this is an excellent piece.

I think we've been dealing with a different group of people when discussing the removal of "invasives," though. Whether wildlife biologist or rural home-owner, nearly everyone I've dealt with reacts favorably to the idea of expelling the invader. Having grown up on Virginia's Eastern Shore, I spent many an afternoon wading through kudzu-choked woods listening to my father lecture on the evils of thoughtless introduction. I can't imagine any Eastern Shoreman (who can identify the plant) telling me that they want the kudzu. Unfortunately, some people "fight" its growth in less than eco-friendly fashion.

I do see people vehemently defend exotics in the "pet" industry. I have little problem with anyone keeping such species in their home - I do myself - but the "release" incidence seems to grow higher every year and this is extremely worrisome.

Anyway, your conclusion/summary (in the linked piece) that "not all exotic species are invasive. Origin of the species isn't the issue; behavior is," is a sound one. I agree that we need to take care before we fall prey to metaphor, but I still see too much rhetoric and not enough education; the fishing tournament that inspired my post is one such example.

I think talk of "alien," "exotic" and "invasive" plants provokes more worried finger-wagging than does talk of animal species. Perhaps this is in part due to Alwin Seifert, the landscape architect, and his association with Nazi Germany. Seifert's writing is still circulating today and, gardening being a more populist pursuit than wildlife management, more people are familiar with the "don't plant exotics" argument, whether coming from a Nazi sympathizer or the well-meaning local, amateur ecologist.

I am only willing to take the parallel so far - as I say in my post, I am ambivalent, equally adamant about the removal of all "invasives," but willing to sit on the question of biological xenophobia and the preservationists' fear of change - and differing between the species in question, and their associated threat, will help a great deal.

Posted by: Hungry Hyaena at April 5, 2005 09:14 PM
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It's interesting that one of the things informing the discussion is our experiences with different advocates, policies, and individuals. My experience is a lot closer to the Hungry Hyaena's. When our college arboreteum staff wanted to try and remove English ivy recently from all lands of the college, to the extent that it was possible, in order to aid native species in our nearby woodland, the enthusiasm from local homeowners, renters and so on was pretty universal in my experience--not because of any enormous personal antipathy to ivy, but because the idea that it was non-native and was threatening natives was sufficiently persuasive in and of itself.

If you think about tost's trout observations, something similar is true--that where fishermen come down on cutthroat/bull etc. vs. rainbow/brown is about half about their feelings about those species, and half about a larger conception of wilderness and conservation which either privileges or does not privilege a conception of the indigenous--but in either case, I don't think the first or even second impulse here is a deeply scientific or well-tested vision of ecological management. The first or second feelings come from somewhere else.

I mentioned purple loosestrife in my original post and I still think that's a very good benchmark to raise. Many ecologists and biologists projected some very dire consequences from its introduction and for the most part, those scenarios have not come to pass. That to me alone says it's time to take the concept back to the drawing board as something which informs the management of the environment--but not to throw the baby out with the bathwater either.

One of the real puzzles here is how to reconcile a sense of ecologies as complex systems, with all that implies in terms of the fundamental difficulty of predicting the systemic consequences of new elements or conditions, and yet not give up outright on the idea of management or stewardship.

Posted by: Timothy Burke at April 6, 2005 08:52 AM
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Timothy, if you have a pointer to the stuff you've been reading on purple loosestrife I'd be much obliged.

Posted by: Chris Clarke at April 6, 2005 10:26 AM
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Elizabeth Farnsworth and Donna Ellis, "Is Purple Loosestrife an Invasive Threat to Freshwater Wetlands? Conflicting Evidence From Several Ecological Metrics", 21:2, 2001.

H. Hager, "Positive Relationships Between Invasive Purple Loosestrife and Plant Species Diversity and Abundance in Minnesota Wetlands", Canadian Journal of Botany, 82:6, 2004.

These are several recent assessments that qualify the impact of loosestrife and suggests that initial forecasts of its effects on biodiversity were exaggerated or inaccurate, though there's continuing debate in the field. There's a good article in a 2001 issue of Biodiversity and Conservation that sums up the case that loosestrife has a negative effect on biodiversity and tries to reply to some of the critical research published to that date, though since then there have been new studies like those cited above.

If you want an example of the lag effect I've been describing, where the research begins to qualify or modify a hypothesis while the policy initiatives originally informed by scientific research take little or no note of the movement in the research, just try googling loosestrife. I found only one significant loosestrife policy assessment that takes substantial note of ongoing debate among researchers--most other removal programs and all the client forms of research that follow in their wake seem to be unaffected, at least in their public presentation--there's no uncertainty, no sense of being involved in a debate.

Posted by: Timothy Burke at April 6, 2005 11:20 AM
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Thanks, Timothy. Fascinating stuff. Here's a link to the Farnsworth and Ellis study in PDF. A couple interesting passages from it:

Our study does not lay to rest the controversy over the effects of this ubiquitous species (nor does it address the impacts of L. salicaria on animal assemblages), but it does suggest that a range of parameters must be measured in the field.

The impact on fauna is rather of interest to me. As far back as the 1940s, biologists were concerned that loosestrife would provide red foxes cover from which to hunt waterfowl more successfully, while depriving waterfowl and muskrats of food plants and changing the physical structure of preferred bog turtle habitat so that the reptiles cannot use it effectively - a problem for a species as rare as the bog turtle.

That structural change is a bit of a hot-button issue for me, by the way, as I watch the progression of invasive East Coast cordgrass (Spartina) toward the estuary of Pinole Creek. (You remember Pinole Creek? This is a blog about Pinole Creek.) The native cordgrass forms looser thickets with clear corridors, on which the endangered clapper rail and salt marsh harvest mouse rely. The east coast species forms thick stands with no openings.

The second passage from Farnsworth and Ellis I found especially worth comment:

Indeed, L. salicaria invasion may be as much a symptom as a cause of factors that influence species shifts in wetland assemblages—an hypothesis worthy of more intensive study.

This is an utterly crucial concept. There's an invasive native species, the cowbird, that is eroding the populations of a couple threatened Western bird species. Cowbirds are brood parasites, like cuckoos: they lay eggs in other birds' nests, forcing the "host" parents to spend energy feeding and rearing the cowbird young that "should" be going to their own young. And the reason this is a problem is because we have increasingly altered the habitat of the West - by cutting down forests and subsidizing herds of cattle - to make the West a more overall hospitable place for cowbirds.

There's a degree to which invasive species, many of which are disturbed ecosystem colonizers, are a problem precisely because we are disturbing the ecosystems they're invading.

I definitely find the notion of triage a compelling one. If it turns out that loosestrife has been a "squeaky wheel," big and prominent but not actually causing the damage that's been feared, I'm all for spending its control budget on something more dangerous, like star thistle. And I agree wiith you, Timothy, that open minds are not only crucial, but - when it comes to government policy - occasionally in short supply.

But Farnsworth and Ellis do concede that wetlands with a high percentage of their biomass made up of loosestrife are likely to have reduced plant diversity, which is accurately measured not just by counting numbers of species but by relative abundance of those species. (A zoo may have more species in it than a forest, but the forest is likely more biologically diverse.) And they seem to propose a triage system within the loosestrife issue as well, spending money to control the tonnage of loosestrife in heavily dominated places.

Posted by: Chris Clarke at April 6, 2005 12:03 PM
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Yes, but what's interesting is that they also focus on the imprecision of many schemes for evaluating biodiversity impacts, and the associated conceptual disorder surrounding the whole idea of biodiversity. (the cite, btw, is from the journal Wetlands--my apologies for that being missing above). The Hager article is a bit more radical on this score--it goes beyond questioning research to date, and quietly challenges the common proposition that ecosystems are typically "tight" or zero-sum, with few unused niches. This, as I understand it (and the Discover article says quite a bit about this) is a more general challenge underway at the moment.

What strikes me is that the whole problem comes back to the difficulty of defining ecosystems and biodiversity--concepts that I think we all recognize have some crucial legitimacy to them, but that I suspect were in complicated, intricate ways taken for granted, where provisional or working heuristics for defining them quietly morphed into assumed empiricisms.

Posted by: Timothy Burke at April 6, 2005 01:53 PM
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Chris - "An invasive native species" sounds like something of an oxymoron. If I understand you correctly, you're using invasive in the context of ecosystems currently in a state of flux, or undergoing radical change. If a species already occurs in a particular niche, and if we're concerned with an upsurge in numbers because of major environmental alterations, that seems to be an issue of population dynamics as opposed to invasiveness.

For instance, if you take a square mile of mountain forest in the Adirondacks with a more-or-less steady whitetailed deer population of 5 deer/ sq. mile, and radically alter that land by adding a dozen 1 acre food plots of high protein clover, you're likely to end up with 35 or 40 whitetails on that section of land. Yet I don't think you could call the additional deer "invasive."

Just to be clear - I don't mean to quibble over language, but I want to make sure I'm following you here. If I'm misunderstanding your point, please set me straight.

Timothy - I'm going to respectfully disagree. I think the problem is less defining ecosystems and diversity than it is in quantifying them. I'm not a scientist, nor do I believe that science has the capacity to answer all the questions we might need to pose, so this doesn't really bother me all that much. But if you're using scientific measurements as your major tool for defining and understanding a particular ecosystem, or a niche within that system, then a failure to convert what we perceive to be phsyical reality into scientific (but still subjective) data is a major impediment to your ability to understand the system in question. In other words, it's not a problem of definition, but of translating, quantifying and understanding information. I hope I've made the distinction clear.

Posted by: tost at April 6, 2005 03:27 PM
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That's not precisely what I mean, tost. There is probably a better word for what I mean - "irruptive" doesn't quite cover it.

The problem is the language. Ravens are native to the Mojave, but they're moving into places they didn't previously inhabit, and their numbers in places they did inhabit are rising.

If we were to define "native" on a sqare-mile by square-mile basis, we wouldn't have the problem in definition. But I bring it up to counter the conflation of "invasives" and "exotics" - the sets may coincide, but the concepts are very different.

Yes, but what's interesting is that they also focus on the imprecision of many schemes for evaluating biodiversity impacts, and the associated conceptual disorder surrounding the whole idea of biodiversity.

I see what you mean, Timothy. I guess I accept that kind of thing as a given. I'm definitely looking forward to the Discover article, either to learn from or pick apart.

What strikes me is that the whole problem comes back to the difficulty of defining ecosystems and biodiversity--concepts that I think we all recognize have some crucial legitimacy to them, but that I suspect were in complicated, intricate ways taken for granted, where provisional or working heuristics for defining them quietly morphed into assumed empiricisms.

"Vegetative communities" is another one of those. There are still people who treat assemblages of plants that happpen to live together as something on the order of a taxon, or a biological entity. Talk to a paleobotanist, and you're much more likely to hear those assemblages described as accidental and shifting, less like a neighborhood and more like a group of people on a subway car at the same time.

The "communities" notion is often useful as shorthand - I can refer to "P-J forest" or "Xeric conifer woodland" to mean "Great Basin forests dominated by single leaf pinyon pine and Utah juniper, with a sprinkling of associated plants that may range from Joshua tree to prickly pear cactus to sagebrush to California flannelbush, with Clark's nutcrackers and Scotts orioles and flickers as denizens," and I save a lot of time by doing so. But I'd go wrong by thinking that there was some inherent organizing principle that assembled all those organiisms into a P-J forest."

Posted by: Chris Clarke at April 6, 2005 09:00 PM
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Yes, very good point--there are good definitions, but weak metrics or quantifications. It's just that I think to make certain kinds of claims (say, that invasives seriously erode or threaten biodiversity) one has to have good metrics or quantifications, and at some point, the lack of good metrics begins to become a problem with the definition itself.


To come at it from another angle: is there any way to separate out "normal" change in ecosystems from "abnormal" change? There's a kind of huge, amorphous counterfactual argument embedded somewhere in a lot of policy initiatives aimed at environmental stewardship that tries to sort these two things out. But when do that, we sometimes misidentify some systems as "normal" in terms of a lack of human intervention--say, the balance of meadows and wooded areas in parts of the mountainous West as seen in the early 20th Century, which was the result of long-term ecological management by Native Americans through the controlled use of fire. Is that "normal"? Don't ecosystems change constantly by their very nature, both in small and incremental ways and in response to small and grand catastrophisms? And so on.

So the better question it seems to me to always ask about environmental change is, "Is this a good change, a bad change, or a change which is neither?" And the answer to that question always, inevitably has an aesthetic side to it, as well as a utilitarian one. Asking it is anthropocentric, but that's as it should be (or at least inevitably will be). Even saying that we'd like systems to change "normally" or "naturally" is a philosophical point: it's not amenable to hard quantification or formal definition, really.

Posted by: Timothy Burke at April 7, 2005 08:22 AM
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Timothy - I agree. The problem, of course, arises from the fact that it's impossible to reach any kind of consensus on good, bad or indifferent. While it boggles my mind, there are folks who think turning the Artic National Wildlife Refuge into a construction zone is a good thing.

Chris - I'm not convinced by the paleobotanist take on "Vegetative communities." I don't see the accidental nature as much as I do the interconnectedness. Those plants don't exist in a vacuum, and everything in a given area influences everything else around it. When I look at a landscape, I don't see random chance. I see an ever-changing mosaic. But that last word is the key. It's a mosaic, a symphony, rather than a thousand monkeys banging away on typewriters.

Posted by: tost at April 7, 2005 09:36 PM
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Well, the people on the subway car interact as well, reading over one anothers' shoulders and jostling and smiling and saying "excuse me." Just because a set of entities is interconnected, however, doesn't mean they "belong together."

We'll have to agree to disagree on the typewriter monkeys. Of course, I've often pointed out that given enough monkeys and enough time, they did not only create the works of Shakespeare but they also invented typewriters!

Posted by: Chris Clarke at April 7, 2005 10:28 PM
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Ah, but you're intuiting the monkeys, postulating that chance and luck and the random nature of the universe have thrown together this capricious existence for no grander purpose, perhaps no purpose at all.

I'm listening to the music.

Now you have every right, and perhaps even an obligation, to doubt what I'm saying. After all, one of my wisest teachers tells his students, "If you believe what I'm telling you, then you're a fool. You're job isn't to believe me; it's to prove me right or prove me wrong."

But to dismiss me out of hand, to question the existence of what the Native Americans call The-Spirit-That-Moves-In-And-Through-All-Things and the Taoists call The Force, without really attempting to ascertain the truth of the matter seems ...... well, the word that comes to mind is “unscientific.”

Posted by: tost at April 8, 2005 10:06 AM
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Do you read comments on old posts Chris?

Apparently shooting kitty cats may soon be acceptable in Wisconsin.

Do you have a reference regarding shooting cats in New Zealand? That's where I'm from, but I don't know anything about it.

Posted by: Greg at April 13, 2005 06:51 AM
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I get email whenever someone posts, so it's as if all posts are new!

My reference regarding NZ fall into that annoying "personal communication" category, chatting wiith land managers and farmers and the like. (Obviously we're not talking about downtown Christchurch here.) But I don't have a citation you can look up, and it's possible my informants were shining me on. I doubt it, but it's possible.

Wisconsin has been much in the news on this, hasn't it? I heard Stanley Temple on the radio yesterday - he's the researcher who concluded six million birds a year are killed by free-roaming cats in southern Wisconsin - and he played a death threat someone had left on his voice mail. Brought back memories of getting my own death threats for publishing "cats indoors" stuff in Earth Island Journal.

Posted by: Chris Clarke at April 13, 2005 07:24 AM
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