Tuesday, August 17, 2010

Is Ecological Restoration Just Gardening?

Lagoon Park in Santa Barbara by Van Atta Associates.  Photo by Saxon Holt
I recently read a wonderful and thought-provoking article by Peter Del Tredici, Senior Research Scientist at the Arnold Arboretum of Harvard University. Del Tredici has been on my radar since he published a subtly subversive book called Wild Urban Plants that I reviewed earlier this spring. This new article posits the question: “Is ‘landscape restoration’ really just gardening dressed up with jargon to simulate ecology?’. Here is a bit more context:

“Implicit in the proposals that call for the control and/or eradication of invasive species is the assumption that the native vegetation will return to dominance once the invasive is removed, thereby restoring the “balance of nature.” That’s the theory. The reality is something else. Land managers and others who have to deal with the invasive problem on a daily basis know that often as not the old invasive comes back following eradication (reproducing from root sprouts or seeds), or else a new invader moves in to replace the old one. The only thing that seems to turn this dynamic around is cutting down the invasives, treating them with herbicides, and planting native species in the gaps where the invasives once were. After this, the sites require weeding of invasives for an indefinite number of years, at least until the natives are big enough to hold their ground without human assistance.

What’s striking about this so-called restoration process is that it looks an awful lot like gardening, with its ongoing need for planting and weeding. Call it what you will, but anyone who has ever worked in the garden knows that planting and weeding are endless. So the question becomes: Is “landscape restoration” really just gardening dressed up with jargon to simulate ecology, or is it based on scientific theories with testable hypotheses? To put it another way: Can we put the invasive species genie back in the bottle, or are we looking at a future in which nature itself becomes a cultivated entity?”  Peter Del Tredici from "Neocreationism and the Illusion of Ecological Restoration," Harvard Design Magazine.

I’ll confess: I am not an ecologist or an expert at ecological restoration. I have, however, worked with ecological restoration experts like Rutger’s Steven Handel. Consider my recent experience on a two thousand-acre agricultural site that we intended to convert into a mosaic of different native habitats. After going through the process of analyzing the site and preparing a restoration concept, my impression was that restoration was really not that different from the design process I use for any ornamental landscape. Obviously, the goals were different and our application of native habitats was based in a much more thorough site analysis. But the end result was the same: we imposed a human concept of what “nature” should be on the site. The end result would be entirely artificial and constructed.
Vernal Pool created in an area that once wasa parking. Van Atta Associates. Photo by Saxon Holt
In addition, our constructed “native” landscape would require years of intensive maintenance to get it established, and decades of ongoing management to keep it native. After this experience, Del Tredici’s analogy to gardening resonated with me.

Del Tredici’s conclusion for designers and gardeners is to “not to limit themselves to a palette of native species that might once have grown on the site.” He argues for using plants that will tolerate the conditions of the site, native or not, particularly in the tough urban conditions.

I have two responses to the article. The first is to agree with Del Tredici’s claim that ecological restoration creates “entirely artificial and constructed” landscapes. It’s absolutely true. It bursts the romantic notion that we can bring back plant and animal communities as they existed before Columbus arrived. It also challenges the myth that native plants are natural, good, low maintenance, and self-sustaining. They aren’t. They require human intervention. The sooner we can lose the mythology that “nature” will come back one day, the sooner we can get to the real work of creating entirely artificial, native landscapes that perform essential ecological services.  See my posting here for more on this.

Boardwalk at Lagoon Park in Santa Barbara by Van Atta Associates. Photo by Saxon Holt
Secondly, I disagree somewhat with Del Tredici’s direction that designers abandon the native only approach. I certainly don’t mind using some non-natives. But implicit in Del Tredici’s assumption is that natives are somehow weaker or less adaptive to the tough conditions of an urban site than some non-natives. I entirely disagree with this point.

Of course, some natives—many of which are ubiquitous in the nursery trade—are not tough enough for urban sites. The natives that are widely available in the nursery trade are mostly selected for their ornamental value. We’ve hardly explored the full potential of native systems to address the environmental challenges of the day. To judge the adaptability of native plants based on the scant selection of natives that are currently available in the trade is preposterous. Mark Simmons, a researcher at The Lady Bird Johnson Center, is doing research that proves that many native plants are much tougher than non-natives and capable of solving many of our environmental problems. I will feature an article on his research later this month.

I love articles like Del Tredici’s. The debate over natives vs. exotic plants is really a debate about what is natural. I look forward to the day when we drop our romantic notions about nature existing somewhere “out there,” and can start to focus improving the ecology of the human-impacted landscapes that we encounter every day.

What do you think?  I would love to hear other reactions to Del Tredici's article, especially any who have some experience or thoughts about ecological restoration.


  1. I'm not sure that the underlying assumption is really that natives are somehow feebler than non=native plants; it sounds to me that Peter Del Tredici's argument is that we simply shouldn't rule out using plants just because they're non-native.
    What strikes me more is the notion that a designed landscape has to be maintained if the intention of the design is to be realized (unless the intention is to see what plants colonize a disturbed site, and how succession may proceed there. The succession idea is one that PDT briefly touched on when he discussed his book this past spring at the Arnold Arboretum, suggesting that researchers use Detroit's endless vacant lots as a laboratory to study how succession may take place in areas colonized by sturdy invasives.) Regardless of what the nature of a plant palette is -- native or non-native, or a mix -- plants have to be tended at least during establishment, and usually for some time after. Countless projects have failed from inattention after installation. Planting a new design is exciting and makes a dramatic visual statement; maintaining that design past installation is so much of a less glamorous endeavor that getting funding for the effort can be tough -- but maintenance is what will prevent a place from becoming an eyesore, being considered a failure, and finally, from being designated the site of yet another capital improvement.

  2. I heartily agree with the points you ascribe to Peter. As no corner of the planet is untouched by human interference and development, no place can be "wild" any more. Elephants in Africa are in large zoos called Reserves that must be managed and defended by people. Plants that once lived in a locale were not "native" in some Platonic ideal sense, but merely passing through based on historical pressures. Those places have changed and expecting the flora present in 1600 to thrive in New York City today is pure romanticism. If we were to "restore" native flora to Missouri, would we restore the oak savanna managed by early native people or the oak forest that pre-dated them?
    And as Global Warming becomes a fact, there is a limit on how much we can be realistically be guided by looking behind us. The Future is - for better or worse - not the Past.

  3. It is most certain that cutting or digging out invasives ... such as Sumac ... will only encourage a multitude more to readily, robustly return. I am witness to it every year right here on my land. The key is to keep cutting throughout the growing season. That is where I fail with parts of the land. I allow them to grow until fall and then have my neighbor mow the areas with his brush hog. If I would maintain the lower hillside three or four times during the summer I could see a difference. Then again the birds would be disturbed from nesting ... and there will be lovely fall colors in those unwanted plants. One year I must follow thru ... when I began these gardens, it was a jungle of ten to twenty feet tall Sumac, bittersweet and briars with no view in site. It would be very helpful if I could find a native that could out grow these plants and keep a few Sumac contained (well most likely impossible... but they do create berries that are high in vitamin C ... birds love them... not to forget too their beautiful colors come fall.) I am also the unwilling gardener of an inherited sea of Bishops Weed ... I have lived with this invasive for many years, but it killed any delicate plants years ago. Lucky for these thuggish plants (and countless wildlife) I am committed to not using poisons of any kind. So I must be diligent, for as you say this is very much as gardening or even more like farming. I think your points about native versus non-natives right on the mark... we should have a larger selection of sturdy natives available. We are moving in that direction I believe... thanks to essays like yours. I look forward to reading the article you link to here and look forward to further discussion on this important topic.

  4. Good article. I actually think gardens are the height of all *good* landscape architecture.

    Most restoration is simply on a different scale than other gardens, and its manipulation or emphasis can vary, esp at the edges or key points. (pruning, weeding, structured design, etc)

    Many LA's at least here in Abq (I am an LA here) seem to not design gardens, they cover the ground and/or just meet code, for whatever purpose. I think that is mainly due to a lack of inspiration and connection to their projects ecoregional context and/or just an iffy client!

  5. Great post! It's all gardening, and if it isn't, it should be. Landscape is always a process.

    To your point about Del Tredici's take on natives, many of the urban survivors featured in his book -- Box Elder, Silver Maple, Poison Ivy, River Birch, Gray Birch, Pin Oak, Red Oak, Fox Grape, and Pokeweed among them -- are in fact native to the eastern United States.

    If native plants can also be urban survivors, it follows that urban horticulture can also be ecological restoration.

    Forty years ago, nobody was planting River Birch; now it's everywhere. What if we gave a similar second look to more of the native plants in Del Tredici's book (of which I've cited only a small sample)? What if we built a new ethic and aesthetic around native "weeds" like Staghorn Sumac, Black Cherry, Sensitive Fern, Virginia Creeper, Goldenrod, Milkweed, and Catalpa? They're here, they can handle urban conditions, and they contribute to the diversity and resilience not only of their immediate surroundings, but (through the migrations of birds and butterflies) of forests and meadows far away.

    This is exciting stuff - keep writing!

  6. I always think that any attempt at a strict native/non-native divide assumes a strict divide between "nature" and "humans," as though humans are not part of nature. In my region of New England, it can be difficult to sort out what a "native" plant is. Are we talking about the plants that colonized this region shortly after the glaciers melted? What about the plants that were introduced by native peoples and by trade? Those introduced by the early European settlers that escaped from gardens and naturalized hundreds of years ago? The line I prefer to draw is around exotic invasives -- plants (like purple loosestrife or Japanese knotweed) that, when introduced by gardeners, have been shown to escape from gardens and destroy valued ecosystems. -Jean

  7. Thomas -- I love your blog, and the conversation it inspires online.

    But I have to ask, was I the only one who saw the caption for the photo of the vernal pool and started humming, "They paved paradise and put up a parking lot"?

  8. As an ecologist who has worked extensively on restoration projects following invasive plant removal, I think that the function of plant species in a restoration project is what will determine whether natives or introduced plants are more appropriate. Functions would include everything from slowing stormwater runoff and reducing soil compaction, to supporting pollinators and providing wildlife habitat. Many non-native plants perform very poorly in the function of providing food and supporting pollinators (see Bringing Nature Home by Doug Tallamy). Establishing more diverse communities tends to equate to better ecosystem stability and that could be accomplished using any plant combinations that weren't overly aggressive. But another point to consider is that by favoring widespread non-native plant species in a restoration project you may be contributing to the homogenization of the landscape. There is great value in restoring locally native communities because they create a more diverse lansdcape overall.

  9. Thanks for the thought-provoking blog. This is an interesting question: "Can we put the invasive species genie back in the bottle, or are we looking at a future in which nature itself becomes a cultivated entity?" To look at this another way, the notion that there ever existed forests or other ecological communities completely untouched by human hands in the last few thousand years is somewhat of an illusion. Here in the US, Native Americans have cultivated the landscape for thousands of years, for example, with the controlled application of fire. Nature to some degree has been a cultivated entity for a very long time. A lot of how or whether we restore nature comes down to human values and resources - For example, what elements of the landscape do we value (e.g. biodiversity) and therefore want to protect or restore? Science can't determine for us what we value. If we value "native" species or communities for whatever reason, then perhaps we want to continue to manage invasive species to protect native species. If we decide that we value something different, then maybe we would go another way. Either way, our choices are often restricted by limited resources. Can we put the genie back in the bottle? Sometimes yes, more often no. Each invasive species, and each invaded community, is unique. It may be good to avoid broad sweeping generalizations in either direction.

  10. hi :)

    i'd like to respond to your post w/ a couple of quotes:

    "As exotic ornamentals leap the garden fence and out-compete the native plants, many creatures are starving to death because they did not evolve with the exotics and simply can’t eat them. …"I’m not trying to recreate the ancient ecosystem," said Mr. Tallamy. "That is gone. I’m trying to create biodiversity.""

    My own sense is that the immediate work that lies ahead has to do with fixing landscape, repairing its ruptures, reconnecting its parts. Restoring landscape is not about 'preserving' lands -- "saving what's left," as it's often put. Restoration recognizes that once lands have been "disturbed" -- worked, lived on, meddled with, developed -- they require human intervention and care. We must build landscapes that heal, connect and empower, that make intelligible our relations with each other and with the natural world: places that welcome and enclose, whose breaks and edges are never without meaning. -Alex Wilson, The Culture of Nature

    no landscapes live in a cloche, of time or space.

    all restoration and conservation is anthropomorphic set in contemporary realities. any of the historic ecology of a site is just among many references that guide the practitioner, not the ultimate goals.

    and yup, landscapes do require ongoing care beyond the establishment phase: management, monitoring, invasive and disease control.

    i've never met anyone who deluded otherwise, so it seriously concerns and rankles me to see that anyone wrote that ecological restoration is premised with this illusion.

    but, thanks for bringing if perhaps it is indeed a notion that is impeding anyone's ecological literacy.

    and thanks for a well-written, thoughtful and well-designed blog.


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