Jeff Gillman on Invasives


JEFF:  There are some general definitions.  But a really good working definition that separates out the different plants into categories by how much they really do to our native ecosystems that you're talking about – in my opinion we really don't have that right now.

AMY:  So it's really just a matter of, "I see some buddleia in the ravine down the street from my house, so buddleia must be invasive?”  Whether it’s actually threatened another plant or not?

JEFF:  Right. Exactly.  And here it’s buckthorn. Buckthorn seems to be taking over at the edges of forests, and I see it too.  Is it an invasive that needs to be controlled at any cost, or is it just a more vigorous plant? Often that question is decided more by politics than science.

AMY:   There was one more really interesting point in your book that I wanted to bring up. You made the point that Europe is a completely disrupted, non-native ecosystem. Humans have been there for thousands of years, chopping down trees and bringing in other plants. I thought about that when I was in France this fall. There really aren't any native, undisturbed areas like we have here.  I mean, the place was deforested in Roman times.  I hear all this talk about advanced forest management practices in Europe that allow much more logging than we allow here—it’s an argument used by the timber industry to justify more clear-cutting—but I drove through a French national forest.  It was a tree farm!  Literally, trees planted in straight rows and cut on 100-acre rotations.  I realized that they just don’t have the kind of ecology we have here.

JEFF:  Yes, and when I made that statement in the book I was really thinking about England in particular. They have been bringing plants in since the 1500s.  They don’t even know whether the pear is native to the region.

AMY:  And yet, as you point out in the book, it continues to be an ecosystem that functions in some way. I mean, England is obviously capable of supporting life — plant life, human life, animal life.

JEFF: But what they have is completely different from what they would have had if humans had never entered the scene.  Nature has a way of finding its own balance.  New plants change the balance, but that doesn’t mean that the balance ceases to exist.

It's called How the Government got in Your Backyard, and it's available at bookstores everywhere.  Check it out.


  1. I love the fact that Jeff Gilman adds some common sense to the mass hysteria. It is only a problem (invasives etc) if it is a desginer species

    the TROLL

  2. Right on, Jeff! I am also very suspicious that the “natives only” movement is more political than scientific.

    And really, what are we trying to achieve? Pre-human pristine? On a planetary scale, that fight is over, and the purists have lost.

  3. Great article. Thanks for shedding some light on this topic that often is surrounded by myth, hearsay, “common knowledge,” hype, and hysteria.

    It really does help to look at other countries and realize that they have survived and even thrived, despite non-natives being introduced.

    Of course, in my garden I want a balance of plantings that I design. So any plant that begins to take over and push others around in my personal ecosystem is unwelcome.

  4. This is great. Thank you.

    My only caveat would be that, as environmental historians point out, all living creatures change their environment. But even if you separate out the actions of humans from other animals (since we can affect things on a huge and conscious scale), places we think of as pristine wilderness in the U.S. were affected by actions of the American Indians. There was a lot of rhetoric among the European colonists about the American Indians as being part of nature in a way the Europeans weren’t, which of course isn’t true. (Either all humans are part of nature, or none are.)

    (And of course none of this is to say that we should not be attentive to the consequences of our actions, so far as we can tell what they are.)

    Anyway, just another voice saying I appreciate this conversation and your thoughtful approach.

  5. I lived on the proverbial island for 20 years where the natives had been pushed over the cliff. That wasn’t done by plants or animals. It was done by man. All the non natives did was fill the vacuum.

    In my 98% exotic, chemical free garden nature was abundant. It vibrated with insect, bird and small reptilian life imported to the island accidentally or more often deliberately. I set a stage and nature responded.

    With increasing frequency due to free trade and a growing imported human population some new pest would arrive and go into plague like proportions. Each one eventually settled in to the mix and the plague subsided within a few years. Sometimes naturally when other creatures discovered it was food and sometimes by human introduction of a predator. For each plague there were just as likely three or more new species who arrived and settled in without being noticed.

    I personally witnessed the day gecko and green house frog settle into the mix of my garden as new species. Nature welcomed them to the buffet. The garden lived on. Balance prevailed and it was a most fascinating thing to watch happen before my very eyes.

    At the same time a growing interest in saving native plants and the few tiny remnants of native plant ecosystems emerged and the invaders once sought out where now reviled in many quarters. But it was far too late. The only hope for native ecosystems was by human management. The only hope for native plants was to bring them into the horticultural trade. That same lesson can equally be applied to continental North America. Invasives may not be causing a natives extinction so much as human activity, but as gardeners we can grow natives as our contribution to diversity and the planets store house of options for balance.

  6. All species tend toward myopia. Including us. And so it is that we cannot see the species that are hurt by our invasive nature, especially amongst all the life we see every day in our own cultivated gardens. Life goes on, in one form or another. I think the question comes to what good native ecosystems can provide humanity. If our answer is none, then off go the fragile. No sweat. If our answer is some, well then we’ll spend money to save that one remaining acre Mr. Gillman mentions.

    I think as gardeners we can appreciate that a garden full of buckthorn is undesirable -all that same undergrowth. A monoculture can be beautiful, as an idea and visually, but more often a diversity of species is desirable.

    I think most people don’t deal in extremes, but just like in politics, it seems that the extremists get promoted and talked about more often than most of us who understand the value of native plants in ecosystems without succumbing to an all or nothing rhetoric.

    But all or nothing sells TV, newspapers, and web logs, doesn’t it?Lastly, it seems that we want stuff for our gardens (and I include myself here) but suddenly we are in a huff when we see someone trying to control those same plants in our greater garden. We are available to tend our private gardens, but who is available to tend the greater garden?

  7. To me the most important thing is that we are temporary stewards of our land. What we plant might be around a lot longer than we are. We have a responsibility to plant things that are easily controlled by future stewards of our property.

  8. I’d like to quietly inject that part of the reason that planting and preserving native species, and preserving them in abundance, is important, is that insects have little chemical sensors on their feet which tell them whether or not plant is suitable food, and whether it is a suitable breeding plant.

    Many otherwise excellent plants have not evolved with our native bugs, and unfortunately, the bugs’ chemical sensors don’t always inform them that a non-native plant is OK to breed on, or eat. They simply don’t see it as an option, and if given the choice between reproducing on something non-native or dying, many of them just keel because they don’t even know that it could be otherwise.

    I hope I don’t need to remind anyone that native bugs feed native birds. Taking out a chunk of an ecosystem by allowing plants that are useless to these insects to take over an area, just isn’t good science.

    The extinction argument therefore is completely beside the point to me. I’m not interested in creating a museum of native plants. I’m interested in preserving the ability of our native insects to reproduce and feed, so their numbers do not diminish, and our birds will thrive.

    Doug Tallamy’s book explains the science behind this. It’s called Bringing Nature Home, and it is a widely-respected book that takes down some common misperceptions about the movement to use and preserve native plants.

  9. I don’t blame Gillman for promoting his book, or Stewart for trying to drive traffic to the blog.

    But it seems to me that both are doing nothing more than setting up strawmen simply so they can knock them down. Genevieve is right: Gillman’s arguments completely miss the point about the need to control invasive plants or the benefits of encouraging native plants.

    It is simply not a reasonable argument to suggest that extinction is the only measure of harm, or that what we should be concerned about is whether some individual buddleia has “threatened” some individual native plant.

    The important questions center around the value of preserving, as much as possible, a diversity of native ecologies. For all the imperfections in our data, ecologists are generally on the same page: as a matter of public policy, it is important that we minimize as much as possible the negative impacts of human disruptions. Striving towards a goal, however vague, of maintaining an enviroment as similar as possible to what we found when we arrived strikes me as superior to any other approach I can identify.

  10. I was looking forward to reading Jeff’s book, but I’m somewhat disappointed by I’ve just read here. It’s a little too easy to read Jeff’s comments and come to the conclusion that because no plants have been driven to extinction in North America solely at the hands of invasive species, that everything ecologically is fine and dandy.

    At the very least, I find his assertion that invasive species have driven no plants here to extinction to be questionable; you can put the blame solely on the expansion of the human species, sure, but you can also argue all day that it’s people who kill people, not the gun that was used.

    There is also long-term evidence that invasive species, entirely without human involvement, do cause massive global ecological changes, extinction included, over long periods of time. We can, of course, point to this and say “invasive species are a naturally occurring event”; however, it benefits more to ask “if we are the cause of such a global event, what is the harm that will come to us if we do nothing?”

  11. Hmmm….I don’t want anyone to be disappointed in what I write — but with this book what I (and Eric) tried to do was to look at situations from both sides — which means that we wrote some things that you won’t agree with — we tried to lay it out there with as many facts as we could — along with the politics. I can assure you that we do mention Bringing Nature Home — though we refused to side with, or against, Tallamy. We think people need to appreciate ALL sides of an argument — and that’s what we tried to do with this book.

    I guess I can see where some of you would think that this post was pro letting invasives go crazy — but what I really wanted to do was to help people see things in a different way.

    Because of the size of a blog post and the mindset of the readership Amy and I wanted to show the side of this issue that most people never consider (whether you agree with it or not is entirely beside the point). I can assure you that in the book there is a more evenhanded approach — though, once again, we don’t take sides in the book — I leave it up to you to reach your own conclusions. I can assure you that you will not like everything that we wrote — that wasn’t our goal — our goal was to help you think about environmental issues in different ways. You’ll be better able to support your position on an issue — and understand the positions of others — if you do

  12. Maybe no plants have been driven to extinction, but I’ve watched in many areas as the bird populations dwindle in direct proportion to the amount of invasive plants that have taken hold. The greater the proportion of invasive plants, the fewer species of birds can continue to live there. Maybe those birds don’t matter to you, but they sure do matter to me.

  13. The points are well-taken, and it does behoove all of us to look at issues like this from more than one angle. Along these lines, I just read recently about research done at Penn State by a biology prof and a grad student regarding invasive species of plants, and how they affect the ecosystem. They marked off an area in central PA that contained lots of non-native, fruiting honeysuckle and studied the bird populations in the area. Areas with honeysuckle had a much larger proportion of songbirds than areas where it had been eradicated. Interesting. They also noted that while the goal is to try to restore an area to its pristine state, it simply can’t be done. Nature is constantly in flux, and many, if not most, ecosystems have already been irreversibly altered by man in some way or other. What one person views as an invasive plant may well have benefits for an ecosystem that haven’t been considered up to that point. Moderation in all things – and really examine all sides of a problem before acting!

  14. Hmm. Thanks for your response Jeff. I may give your book a shot, now that I know you were deliberately trying to show just the “other” side of the debate here in this blog. I had previously decided to pick up your book because it sounded like the book presents both sides of the various issues. I’m sick of reading facts and opinions only supporting one extreme or another.

    I’m not keen on having anyone assume that I am only familiar with one side of an issue, just because I lean towards that side, but meh. I suppose that’s true of many people.

  15. It sounds to me that the authors are saying, “If rape is inevitable, then relax and enjoy it.”
    Invasives do more than push out native plants–they destroy ecosystems–the insects that used to feed on the disappeared plants, the birds that fed on the insects, the animals that fed on the birds; the soil, water, and air qualities that the plants affected by their root and leaf systems; etc., etc., etc. Deep-rooted prairie plants absorb all the rain water that falls on them thereby preventing flooding is one example.
    Invasives change ecosystems from complex systems that are self-sustaining to ever simplified systems that have to be “managed”. whether it’s a lawn, a corn field, a perennial garden, or a weed field.
    Here in the Midwest, our prairies are gone, our woodland savannas are being destroyed by Buckthorn, Amur Honeysuckle, Oriental Bittersweet and more. These alien shrubs leaf out early and drop their leaves late shading the ground for a far longer period of time than native shrubs and trees do. This characteristic prevents the native undergrowth from emerging that then results in soil erosion. How is any of this OK?

  16. There’s one question I always feel like asking people who are adamant about the dangers of invasive plants: How big is your house? Because I strongly suspect that more plant habitats have been compromised and lost and more species threatened by overdevelopment and overbuilding than by foreign invasives. Plant all the natives you want but it won’t be enough to balance things out if we keep building and living in McMansions.

  17. I can honestly say I do not know the science -methodical observations and testing of those, of birds and other life relative to native or non native plants. However, I can say that I have a general understanding of both sides of the human issue, which has a lot to do with desire, practical concerns, cultural norms, and spending.

    What I don’t understand is how a concern for native plants and or ecosystems is political. To me there couldn’t be a more apolitical concern. Is it that money going to protect a patch of woods is a physical benefit to me and my kind and therefore subject to political process and therefore political? But doesn’t that patch of woods benefit all of us near it? Is it that democrats associate with ‘environmentalists,’ therefore native plants have become political? Or is it the libertarian dream to be an individual unto himself, never anyone asking anything of him and his will, that makes invasive plant bans political?

    I think we will find all political stripes arguing all corners of the debate about what to do or not do with invasive species. I also think that it is simply a clever device to use ‘GOVERNMENT’ in the title of a book on invasive species during a period in which anti-government fervor runs higher than usual (at least if we believe news reports and opinionators).

    I have not read this book, can’t say I won’t. Despite the mixed messages of the book cover, I hope that it provides useful information for leaders who are looking to make sound and beneficial policy.

  18. I live in a 750 square foot restored Sears bungalow built in 1927 on a 60′ x 120′ lot. I have rich prairie soil in which I grow designed prairie and savanna gardens.

  19. Jeff’s book definitely presents both sides–that’s the whole idea behind the book–but my reason for choosing the few points I did was that they are thought-provoking ideas that might challenge us to consider other viewpoints. We all tend to get very entrenched in our views and very angry with anyone who disagrees with us, and it doesn’t hurt to consider other perspectives.

    I mean, really, what about England? The United Kingdom was well on its way to deforestation before Roman times, and the Roman empire deforested much of Europe. Was that a good thing? No. But it happened 2000 years ago, not 100 or 200 years ago as is the case here. Surely it’s at least interesting to ask the question–are they really so bad off in a completely transformed, totally worked-over ecosystem that was last “natural” or “wild” thousands of years ago?

  20. Claire Span–my point EXACTLY. I promise to worry about invasives when we’ve eliminated all the asphalt. Until then, I plan on enjoying my orange roadside daylilies and yellow flag iris.

    Also, the idea of “preserving” anything is ridiculous, given the intense pace of adaptation in plants. Check out David Briggs on micro-evolution.

    And Susan, on my own property, I’ve noticed such intense wildlife activity in a stand of theoretically invasive reeds, that you literally cannot have a conversation in my house at dusk with the windows open in summer. The birds are just too loud there.

  21. The tension between wilderness and civilization is something we have trouble with at a number of levels. The fact is that beautiful places like the Pawnee National Grasslands and Kew cannot exist on the same patch — not even within proximity to each other (and not only for reasons of climate!). Based on the interview, I can tell that this is a book I want to pick up and spend some time with. Thanks.

  22. I think this post might have missed the point. I think the real question is “where is the balance between the costs and benefits of non-native plants?” Implying that there are no costs, because the introduction of a butterfly bush is not the same as a nuclear holocaust, is not really helpful or interesting science.
    This issue is too complex to simplify into two polarized opposing sides.

  23. After seeing your posts about this book, I got a copy through interlibrary loan. It’s really a good reference and an easy read.

  24. I am grateful to Jeff and Amy for adding their voice to this discussion.

    If the point of the book is to encourage people to think critically about important issues then, well, I guess it’s hard to to criticize that goal without sounding like a crank.

    However, I don’t accept the premise that there are necessarily two sides to every issue. “Reasonable people, equally informed, seldom disagree.” And I think that most reasonable people would agree that the continued use of invasive plants in modern landscapes is a poor choice from an ecological standpoint.

    Now, I can see how people might disagree on precisely what that means from a public policy standpoint. Should invasive plants be banned? Should tax dollars be used to remove them from public lands? If so, which plants and which lands? And so on.

    But that discussion is fueled by intelligent and reasoned discussion. If this book contains that, then great. But if this interview and the subsequent discussion contain a representative sample of the arguments against the use of native plants, then I conclude that that the anti-native argument is empty.

    The case for controlling invasive plants, or planting native ones instead, does not hinge on plants being driven to extinction or on some utopian view of “preserving” an unspoiled landscape. The case for controlling invasives and using natives instead depends, rather, on a reasoned conclusion that natives function in our ecology better (on balance) than alien plants.

    Are some alien plants worse than others? Of course. Might invasive aliens be better than asphalt? Maybe. Would a landscape composed entirely of alien plants support some life? Sure. But those questions miss the point.

    The real point is that, given a choice between an indigenous plant and an invasive alien, the indigenous plant is – all else equal -the better ecological choice. And the number of situations in which that general finding does NOT hold true are few and far between.

  25. Another consideration I haven’t seen mentioned here – global warming. We are changing all the ecosystems of the planet rapidly. We may have numerous healthy microclimates here in the high northern desert, and in Seattle where my daughter lives, but they won’t be the same as they are now – and they are already noticeably different from fifty years ago. We gardeners are hosting plants and animals that may provide the survivors of the new world our grandchildren will be struggling in.

    Perhaps a particular native species will carry on farther north, or uphill from where it grows now, but more is changing than the temperature. Symbiotic species, sunlight and day length (if we’re talking about moving to the new location to match old temperatures)and rainfall are some of the changes. What is true now may not be true in fifty years, or even ten.

    We can still talk about whether or not a particular newcomer is bad news. But I think that traditional ecosystems everywhere are gone forever.

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