Links and Winks—: The Design of Ecological Corridors

"Once upon a time. . . ."

This is our invocation of memory, but also of fantasy. The efforts being made to design ecological corridors are grounded in the memory of a more connected physical landscape, with a more reliable ecological function. Our past human actions have given us structures that dominate the natural landscape, severing demographic and genetic connections. Human and ecological health needs, now urgent, will require stitching together the pieces. Is our stitching in time? Can a rendered ecological fabric be repaired?

Success will require links among professional disciplines, not just between landscape parcels. In this Special Issue, we address a variety of perspectives necessary for progress: scientific fact-finding; architectural design explorations; public policy initiatives; and scale of action, from microsite to continental. We also offer journalistic scope from detailed, analytical black-and-white figures, to the knockout, 16 pages of living color of landscape architecture innovations. Have we gotten your attention? There's a design world out there for the ecological community to meet. Invite them over (a wine bar will do)!

The creation of ecological corridors is deliciously complex. The scale of concern varies in space. Movements of small animals can even be stopped by a concrete curb, but this barrier can be remedied by an acute-angled street border (Figure 1), a design feature that is, alas, rarely used. The scale expands through road crossings, highlighted by the elegant designs in this Special Issue, then through neighborhood greenways and the rails to trails movement (e.g., www.railstotrails.org) across many kilometers. Tens and hundreds of kilometers can be joined by regional networks and continental efforts such as the Yellowstone to Yukon conservation initiative (y2y.net), as discussed in this issue's Perspectives and Restoration Notes sections.

Sometimes the large-scale networks are not spatially continuous. For example, in the well-known case of securing whooping crane (Grus americana) migration pathways, the need was not real estate between Texas and northern

Figure 1.

Acute curb cuts allow the movement of small animals such as turtles, lizards, and small mammals across concrete barriers that may be only several centimeters high but can be lethal. This structure is at the Sebonack Golf Club, Southampton, New York.

Canada reserves, but rather education, as much of the area was a flight path, not an earthbound trail (Figure 2). Educating the public that those big white birds were not to be hunted was a major effort to maintain this grand species (ICF 2012). Similarly, in Costa Rica, some moths required land both in the mountains and in the dry forest lowlands (Allen 2001) to complete their life histories; high elevation land was needed to secure the migration destination. Large-scale corridors, whether earthbound or aerial, will need a level of public understanding that is sophisticated.

In a time of changing climate, the ability of many species to move large distances is urgent. We know that species have moved across hundreds of kilometers during geologic time scales as the glaciers retreated (Davis 1983). Climate change is the anti-glacier, a movement of heat, not ice, across the hemisphere. The role of corridors is more urgent now than in the times before humans carved up the landscape.

Figure 2.

Whooping crane (Grus americana) habitat in North America is divided between coastal Texas and northern Canada habitats. Many hundreds of kilometers must be crossed in the air to migrate from one area to the other. This is a necessary part of the species migration corridor but is not represented on the ground. This aerial corridor was the source of much mortality before an intensive education campaign aimed at waterfowl hunters. (Reprinted with permission from the International Crane Foundation).

Variation in scale of corridors is a product of species niche requirements and the complex reasons why plants and animals move at all. (Plant movement can be by pollen, seed, or vegetative structure, such as the shed twigs of riverine willows [Salix species]. Plant movements may be slow and not apparent, but they are real.) Lewontin (in Baker...