Invasive Species and Botanical Xenophobia


Summer temp journalists are here again. Today, Swedish Broadcasting’s radio news ran a really silly piece about invasive species. It made two main points: a new foreign species of plant or animal is discovered every month in Sweden, and some of them are poisonous. It’s basically a case of botanical xenophobia. The journalist also made the astonishing claim that these poisonous species pose a threat to the country’s biodiversity!

Poisonous plants and venomous animals are rare in Sweden, whose flora and fauna are quite poor because of the cold climate. On the other hand they are common in rich tropical biotopes. And the reason that biodiversity is plummeting in the Amazon certainly isn’t the presence of venomous frogs.

Invasive species of course increase an area’s biodiversity, at least in the short-term perspective. People are looking at ecology on the wrong scale level. Wait a thousand years before you decide whether a new arrival is good or bad. Almost all of Scandinavia was under two kilometres of ice until 10,000 years ago, which means that our ecosystem is a recent cobbling together of whatever species happened to be available when the ice melted. Nature’s way is continuous change. And to see a stable ecosystem re-established now, people would simply have to move out.

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30 thoughts on “Invasive Species and Botanical Xenophobia

  1. In Bowling for Columbine Michael Moore made the connection between botanical / meteorological xenophobia and its human variety … Threatening foreign species and weather contributing to a siege mentality and paranoia … the result for society being that you need a National Rifle Association to defend against the venomous frogs and invidious hurricanes!


  2. I won’t be too hard on you, because after all, you’re an Archaeologist, not an ecologist. I doubt other commenters will be so forgiving.

    I agree that not all exotic species are invasive. North America has many many exotic species, and most fit in just fine, without causing any trouble. But some percentage do cause trouble, in some cases enormous trouble. And it can very difficult to predict which ones those will be, or what form that trouble can take. It might not even be the plant itself, but some pathogen that it carries that can wipe out a native species.

    Look up “kudzu” and try telling me with a straight face that dropping random species into an ecosystem always increases biodiversity.

    It’s not just paranoia or xenophobia, it’s a real problem.


  3. Martin, you’re making a serious mistake here. A lot of things that aren’t really a problem for “the ecosystem” or “the planet” can be a major headache now. Even Global Warming is not a problem over tens of thousands of years – the ecosystem will adapt nicely enough, and it’s been through worse – but it’s a problem for people, here, now. Surely that’s what matters?

    Lake Victoria is one of the most drastic examples of the effects of invasive species.


  4. Maybe we can agree that a species needn’t be either poisonous nor a threat to biodiversity nor exotic in order to pose a problem to people. Also, perhaps, we can agree that being poisonous does not make a species a greater danger to biodiversity.


  5. Can we agree that waiting 1000 years is a terrible stewardship plan?

    Actually in my area, poisons used by the roots of garlic mustard (Alliaria petiolata) do give me more cause for concern, just cause that is one of it’s advantages in combat with our native plants, but that is mostly trivial – every species has its tricks. Unchecked this plant may cause local extinctions, and it can become so common that the forest energy flux does seem decreased to me (sorry, no measurements, but just try to find any insects or herbivores associated with that stuff in north America).

    As for aesthetics – the kids don’t know what trillium are anyway.


  6. No, it is not xenophobic to worry about invasive species, and invoking that oh-so-politically correct association doesn’t support an argument. Introducing species may or may not cause problems for the species already there, or for human activities, but it is not something to take lightly. The most glaring cases are those where the local flora or fauna evolved without a major ecological type (e.g., New Zealand without any terrestrial mammalian predators), which leaves the local species at a loss to figure out what to do (“gee, what’s that furry thing with the teeth?”). But kudzu, or prickly pear in Australia, or zebra mussels, or … show that it’s not necessary to have that factor operating.

    Wait 1000 years? Why?


  7. Introducing a highly successful exotic species into an ecosystem throws it off balance, which looks really scary to someone with a memory stretching less than a century back. But if you leave the area in peace and wait 1000 years, you won’t find the area devoid of life. You will find a new balanced ecosystem, possibly incorporating the former exotic species.

    All of this, of course, only holds true if the ecosystem isn’t constantly prodded and bombed by a growing agro-industrial human population.

    My main point above, though, was that the journalist’s emphasis on some exotic species being poisonous smacks of hysterical fear.


  8. To varying extents, the people living in any region become accustomed to the plants and animals they live with, and they are not likely to find it convenient economically or aesthetically to have species that are beneficial displaced by species that may be less beneficial or even noxious. Sure, folks living 1000 years hence in a given place may have different plants or animals to live with as a result of species being purposefully or accidentally introduced by their ancestors, but we aren’t those people, and it is as much our duty to preserve our local faunas and floras as it is to preserve any worthwhile aspects of our cultures. Some drastic changes in local floras occur not as a result of introduction of other floral elements but rather as the result of the introduction of organisms that cause the demise of highly desirable species of plants. In the USA, this has happened with two important tree species, the American chestnut and the American elm, and it appears to be happening now to several important species of the genus Fraxinus, one of which, called white ash, has traditionally been used in the manufacture of things like tool handles, hockey sticks, and baseball bats. The stately elms lining the streets of some cities like Ann Arbor, Michigan were replaced with white ash, only now to be wiped out by a beetle from China called the emerald ash borer. The losses of the American chestnut and the American elm were caused by bacterial and fungal diseases that came from Europe. Your point of view seems to suggest that we should relish such faunal and floral changes as increases in diversity and encourage them by introducing plants and animals willy-nilly throughout the world.


  9. I would be unhappy if, for instance, common tree species that I grew up with disappeared from my area or dwindled sharply. But their ecological niches would of course soon be filled. And then, in my old age, I might tell my great grandchildren about the lovely trees I used to climb as a child. I believe they would be sympathetic, but still, the children would be quite right to point out that “Great-gramps, we too have trees that we can climb”.


  10. “Let’s talk about kudzu 1000 years from now.”

    –Let’s talk about global warming a thousand years from now.


  11. …but still, the children would be quite right to point out that “Great-gramps, we too have trees that we can climb”.

    There is, of course, a lot more to a tree than climbability. They provide food for the other organisms that feed on them, and when the trees disappear, so also do some of the species that rely on them fully or in part for sustenance. Such is the complexity of the web of life.

    And the cultural importance of some kinds of trees may be significant, as would appear to be the case in northern Europe with the linden or lime tree. Without it, you wouldn’t have had the Swedish surnames Lind, Lindberg, Lindgren, Lindholm, Lindquist, and Lindström. Moreover, Sweden’s most famous botanist and zoologist wouldn’t have had the surname Linnaeus, which is Latin for linden, which his father chose after a large linden tree on the property of the church in Stenbrohult parish where he was a clergyman.


  12. 1000 years? Goodness what a short timescale, you do realise that the sun is going to implode eventually, and that this will all be an irrelevance?

    On the other hand, perhaps there are considerations of scale. Most of us have a concern for the world we inhabit now, and the bits of it we are in contact with.

    In the long term it doesn’t matter a bit if giant hogweed can now flourish in Sweden. It doesn’t matter in the short term so long as Dr Rundkvist’s children or grand children aren’t allergic to the hairs, and it isn’t growing where they now play happily.


  13. Can we generalise from giant hogweed and arrive at the belief suggested by the journalist, that all of the exotic species found in Sweden are dangerous?


  14. “Kudzu has long been thought of as a nuisance, but recent research has revealed that Southeastern landowners might be sitting on goldmines: kudzu can be used to produce energy. A new plant in Tennessee aims to turn the stuff into ethanol, a great alternative to corn since it doesn’t require irrigation.”(

    And what you can’t turn into ethanol, have a look at the Japanese people, start eating it.

    there are always two sides of a coin. Maybe we shouldn’t be so afraid of change.


  15. “All of this, of course, only holds true if the ecosystem isn’t constantly prodded and bombed by a growing agro-industrial human population.”

    I will agree the poison plant thing is off. On the other hand your quote is the “all other things equal” fallacy. The ecosystem -will- be prodded and disturbed by humans for the foreseeable future. That is why invasive’s are there and what makes them dangerous. In the upper Midwest US we are seeing mono-cultures taking over in a lot of places. Yes in 1000 years things will be different, but a guy from a few miles from where I am, Aldo Leopold, proposed this thing called a “land ethic” where we value diversity and locality in ecosystems.

    Human use has weakened and made very brittle many interrelated local systems. Invasives are the killer stroke for a lot of species. It is quite bad. From garlic mustard to buckthorn to zebra mussels to millefoille to … well there are many more. The local ecosystem is being blasted and even farmers around here are starting to notice bad things.


  16. Let me hurl an additional insult on top of “Archaeologist” @2 – it’s “European”.

    Have you ever seen any tragedies caused by invasive species, or ones that cost billions of dollars, in Sweden?
    My world has changed, and it is not just bad (costly), it is ghastly. And I live in an average N American place, nothing near as cool as NZ, Hawaii, Madagascar.

    I’d like the next generations (not evolutionary time spans away) to have more than just a crumb of the loaf that once was, meanwhile consoling themselves with philosophies that widespread human-caused extinctions are actually beyond good and evil.


  17. Have you ever seen any tragedies caused by invasive species, or ones that cost billions of dollars, in Sweden?

    Not that I can think of. There’s the crayfish fungus that kills the native crayfish species, and the mink that kills a lot of waterfowl. I wouldn’t call either a tragedy, more a nuisance. The big problematic invasive species is of course H. sapiens.


  18. The Ocean Planet has an invasive exotic problem alright, and it’s a real weed of an African ape. Disperse the propagules of everything randomly from orbit, I say, and let flourish what will. And let go extinct what will. Get it over with.


  19. Most of the animal species which have caused trouble to those indigenous (of course I realise the problems connected with the concept of ‘indigenous ‘and that every eco-system is dynamic by nature) in Sweden have been deliberately introduced by man. Thids holds true for the canadian goose (branta canadensis) which has threatened the population of bean goose (anser fabalis), previously very common in Sweden. This holds true also for the mink (mustela vison), the signal crayfish (pacifastacus leniusculus) that Martin mentioned and for the brown hare (lepus europaeus) which is competing with the lepus timidus that used to be our only variant.

    All the talk about kudzu scare made me think of ‘Return of the giant hogweed’ by Genesis – they should have used that song as an introduction in the SR broadcast.

    The latest rage over invasive species in scandinavia is the spanish slug called arion vulgaris – gardeners hate it, since there seems to be no predator efficient enough to keep it at bay. Some has taken to introducing muscavy ducks in order to stop the slug. If we go on like this, we will eventually have to keep tigers in our gardens.


  20. Tell the gardners to make some beer traps. Slugs love beer.

    You get some plastic bottles, punch some holes in them, put some beer in and put them around the garden – the slugs and snails fall in and either drown or die of alcoholic poisoning, I’m not sure which.


  21. They’vre tried that but according to reports it caused riots, slugs behaving drunk and disorderly, getting into fights and so on. 😉


  22. They used the wrong beer, obviously.

    For Arion vulgaris you need to give them Spanish beer, or they turn really nasty 🙂


  23. So, the “Great Reshuffling” is nothing more than a social science experiment? Botanical xenophobia is silly, but not as silly as the notion that the phenomenon of biological invasion is nothing more than background noise from natural processes. Invasive species denial is beginning to look like the liberals and lefties answer to climate change denial on the right. In the face of overwhelming evidence that the phenomenon is both unnatural and harmful, both camps assert that we need some more perspective. Lefties often see an analogy to race purity that causes them to cringe, and I cringe too. A better analogy is corporatist homogenisation of the food industry. Make no mistake – invasives introductions fueled by global trade is producing the biological equivalent of fast food.


  24. You mean that each climate zone will eventually have identical flora and fauna around the globe? I find that highly unlikely. The exotics always interact with the locals. And the moment we stop moving species around (for instance, if H. sapiens is hit by a major flu pandemic), the inhabitants of each local biotope will start to diverge genetically, until global variety is reinstated. What we’re seeing now is a brief blip seen in the longer perspective.


  25. The 9 extinct birds from Chatham island were, in part, made extinct by domestic cats. Never the less, down with the xenophobes who got rid of the cats! And as for those racist Aussies with there attempts to eradicate bunnies…

    I agree that what we do now is unlikely to affect total biodiversity in a million years time, but it’s hard to care what will be around then as it’s unlikely that I or my descendants will be around. We scarcely exist in evolutionary time.

    As an archaeologist, you must like being able to recreate the past from an artefact. As a phylogeographer, I like to be able to infer the past history of wide time spans from the current distribution of animals and genes. Moving plants and animals around (and making them locally extinct) messes all that up and loses our link with the past. Which is sad.


  26. Martin, your remark about kudzuström etc is hilarious haha.

    And you are right. It happens all over again I might add: we see change, we see newcomers. We don’t like the change and we attribute the change to the newcomers and not to ourselves of course. So the newcomers ar a threat. All of them and therefor they are worthless and can be eradicated. Like humans in culture and creatures in nature. There is little difference. Your remark about adapting species is already happening: the caintoad is changing in Australia, becoming less poisonous and creatures already have learned now to eat them. And zero creatures have become extinct because of this toad..Mustela vison is mentioned here. The European mink has gone and it has been researched: it has nothing or very little to do with Mustela vison. It has everything to do with us. BEsides, despite the prediction of a weakening europena mink where they interact (less food for the smaller European one), the opposite is happening.

    The xenophic attitude of ecologists is no different than those in culture and therefor fiercly attacked when mentioned. But that doesn’t help: it is virtually the same. It hinges on examples, facts (look up Sax and Gaines, peerreviewed rsearch) show a very different picture. Like some others have said: people are allergic to change and develop a single sided view on newcomers. Again. And we start to kill..again…and we deny we are wrong. Again.
    The “problem” on this planet for biodiversity is habitatloss, hunting and not invasive species. Again: read Sax and Gaines, 2008. They have DONE the research..


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