Before continuing to speculate on this topic, I would like to briefly review some of the art movements and projects that one might consider as sustainable art or precedents for it. The projects fall into several categories: art that engages with the land or landscape; art that incorporates sustainable practices such as recycling; and art that responds to social issues through the production of objects or discourse. Within the first category, artists have engaged with the land in different ways, not all of which can be seen as environmentally sustainable. Various terms such as "environmental art," "earth art," "land art," and "eco-art," have characterized these interventions. Walter

Maria's Lightning Field (1977), Michael Heizer's Double Negative (1969), Dennis Oppenheim's Time Pocket (1968), and Robert Smithson's Spiral Jetty (1970) [ FIGURE 1 ] represent artists' intentions to alter the landscape, either by making cuts, gashes, or holes in its surface, forming new shapes from large masses of earth, stone, or other materials, or, as with De Maria's Lightning Field, filling a large field with metal rods lined up in symmetrical rows.

Other artists produce sculpted or constructed forms that they place in the landscape to enter a dialogue with it. These include Mary Miss's Sunken Pool (1974) and Alice Aycock's Circular Building with Narrow Ledge for Walking (1976), the latter a structure that invites participation from the public. A third group of artists work with processes found in nature. Their projects are exemplified by Hans Haacke's Ten Turtles Set Free (1970) and Newton Harrison's Slow Growth and Death of a Lily Cell (1968). Related projects include Alan Sonfist's Time Landscape (1965-1978-ongoing) and Joseph Beuys's 7000 Oaks (1982-1987) [ FIGURE 3]. Sonfist obtained the use of a land parcel on LaGuardia Place in New York City, where he planted trees and shrubbery that would have grown in the precolonial forests of the area, while Beuys's project, which he initiated in 1982 for documenta 7 in Kassel, Germany, involved reforesting the city of Kassel. One of the largest environmental art works ever executed, it was finally completed in 1987 after he died

In recent years, art in the landscape has taken on a different meaning when it has been used to reclaim sites that were previously abandoned or even subject to some destructive force. To create Wheatfield-A Confrontation (1982), Agnes Denes planted and harvested two acres of wheat on the Battery Park landfill close to Manhattan. As a discursive act, the project demonstrated how a piece of wasteland could be brought back to life, although it ended without transforming the landfill permanently. In Germany, Herman Prigann, who created the Terra Nova project (1996-2000) to reclaim damaged or destroyed landscapes, turned Rheinelbe, a former coal mine area near Gelsenkirchen that had become a garbage dump, into an archeological field replete with traces of former buildings, stone sculptures, and a major landmark called the Skystair.

Recycling is another activity that contributes to a sustainable environment. Since the 1920s, making art out of previously used materials has been one of the significant strands of modernism, although until recent years it has not been framed by a discourse of ecology or sustainability. While Kurt Schwitters made hundreds of collages from the printed flotsam and jetsam of Weimar Germany, critics have never considered him to be an ecological artist. The same is true for John Chamberlain, who reclaimed cast-off auto bodies, which he crushed and shaped into large metal sculptures. On the vernacular side, the "muffler men" made by folk artists in the American Southwest or the toy cars, trucks, and motorcycles created by street artists in Tanzania and other African countries are also examples of industrial waste that is turned to productive use.9 Mierle Ukeles, who has served for almost thirty years as artist-in-residence at the New York Sanitation Department, dealt with the problem of waste a different way. In her project Flow City (1983-present) [ FIGURE 2], she transformed a garbage-recycling unit of the Sanitation Department into a site where the public could observe how garbage is disposed of in actuality and on a video screen. As part of the project, she created a walkway, bridge, and viewing wall that were made of recycled materials.

Art that responds to social injustice is perhaps the largest category that might belong to a culture of sustainability, although it is scarcely visible as such since many artists make art based on social concerns without relating their work to sustainability issues. Within this category, for example, would be Joseph Beuys's well-documented and numerous political actions that include the information office he set up as part of his Organization for Direct Democracy (1971), his founding of the Free International University for Creativity and Interdisciplinary Research in Dьsseldorf with the writer Heinrich Bцll (1974), and his involvement in the genesis of the German Green Party (1979).