sisu: "It looks an awful lot like gardening"

April 21, 2004

"It looks an awful lot like gardening"

Bittersweet (Celastrus scandens) often form continuous cover over large areas and thus slow down reforestation.* (Harvard Design Magazine photo) Update: "Bittersweet my butt! That picture is just plain ol' kudzu!" says mhking in the comments.

"Call it what you will, but anyone who has ever worked in the garden knows that planting and weeding are endless," writes Peter Del Tredici, Senior Research Scientist at the Arnold Arboretum, in "Neocreationism and the Illusion of Ecological Restoration" in the current issue of Harvard Design Magazine. We've studied with Peter and even worked for him one summer, and his humor and wisdom and down-to-earth common sense come shining through in the article:

Within my own narrow field of expertise, plant ecology, the use of exotic versus native species in designed landscapes is an issue that seems to bring out the worst in people, not unlike the debates over gun control or abortion . . .

What’s striking about this so-called [landscape] restoration process is that it looks an awful lot like gardening, with its ongoing need for planting and weeding . . . 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?

"The answer to this question lies in an understanding of the concept of ecological succession, the term used to describe the change in the composition of plant and animal assemblages over time," notes Peter:

In the good old days (prior to World War II), ecologists tended to view succession as an orderly process leading to the establishment of a “climax” or steady-state community that, in the absence of disturbance, was capable of maintaining itself indefinitely. I refer to this as the Disney version of ecology, stable and predictable, with all organisms living in perfect balance.

Following World War II, a younger generation of ecologists began challenging this static view, eventually formulating the theory of patch dynamics, which viewed disturbance as an integral part of a variable and unpredictable succession process. The key concept here is that the nature, timing, and intensity of the disturbances are critical factors --along with climate and soil -- in determining the composition of successive generations of vegetation. From the contemporary perspective, the apparent stability of current plant associations is an illusion; the only thing we know for sure is that they will be substantially different in fifty years.

"To assert that planting native species will restore the balance of nature is just another way of ignoring the problem":

Native plants are great, but without ongoing care and maintenance, they will die just like all the other plants we try to cultivate. The concept of implementing ecological restoration in an urban or suburban context is particularly problematic. With all that pavement, road salt, heat build-up, air pollution, and soil compaction, the urban landscape is an inhospitable place for plants. The critical question facing landscape architects in these situations is not what plants grew there in the past but which will grow there in the future.

What I find particularly depressing about the “native species only” argument is that it ends up denying the inevitability of ecological change . . . To deny the inevitability of ecological change or to pass moral judgment on it is to deny the reality of organic evolution.

And here we think Peter puts his finger on what's really going on here:

Indeed, the very same processes that have led to the globalization of the world economy -- unfettered trade and travel among nations—have also led to the globalization of our environment. The main difference between the two, however, is that the environment is more complicated and harder to control than the economy.

Try telling that to Daniel W. Drezner, Pete.

"So what can landscape architects, designers, and contractors do about these impending changes? My advice is simple: don’t limit your planting designs to a palette of native species that might once have grown on the site":

Invasiveness is but one of several criteria that should be used when selecting plants for a given site, and sustainability means that the final planting list is based on a realistic evaluation of site conditions rather than on a romantic notion of the past.

*These vines spread across any young trees that might have become established and pull them down, shade them out, or actually strangle them by twining tightly around their small trunks. Neil Jorgenson, A Sierra Club Naturalist's Guide to Southern New England (Sierra Club Books, 1978)

Note. What it took to produce this post has taken years off our blogging life. Typepad has been utterly unreliable to the point of our losing material we had already saved, being unable to access first our blog and then our editing program for hours . . . This is not your mother's blog host (^*)

Posted by Sissy Willis on April 21, 2004 at 04:12 PM in Plantarum | Permalink