Urban Design Without Ecological Risk
A Texas environmental design team argues that exploration of our native flora, not acquiescence to invasive exotics, represents the real “Brave New Ecology.” 

By Mark Simmons and Heather Venhaus, ASLA

Courtesy Jane Sebire/Pollen Photos

In his recent article, “Brave New Ecology” (Landscape Architecture, February), Peter Del Tredici, a plant scientist at the Arnold Arboretum, suggests that in urban environments native species rarely offer suitable options, and a plant’s geographic source is less important than its ability to establish and thrive in this unforgiving environment. He bases his argument on three assumptions:

• Plant composition of urban landscapes has been permanently altered, and horticultural use of exotic species does not represent a threat to ecological stability or function. Further, the use of invasive plants is in many ways preferable (in his terms, “sustainable”) because they require little or no resources or management to grow in the urban setting.
• The underlying concepts and science of ecological restoration represent a misguided idealism that has minimal application in urban landscape design.
• Native plants have little place in urban design because the site characteristics have often been so dramatically altered from their original state that natives cannot thrive.

Here at the Landscape Restoration Program at the Lady Bird Johnson Wildflower Center in Austin, Texas, we argue that Del Tredici’s approach, if adopted, represents a lost opportunity for urban designers to take advantage of our rich, underused native floral diversity and to apply the growing scientific understanding of ecosystem form and function to project design. The true challenge to urban designers who pursue ecological sustainability is not only to strive for designs that require fewer inputs in terms of water, fertilizer, and maintenance, but also to consider the effects that plant selection will have both on and off their project site.

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