“Healthy Building,” Resurgence, March–April 1993
An ecotone is a place where two or more ecosystems meet. For example, in San Francisco Bay, fresh water from the Sacramento and San Joaquin rivers flowing from the mountains meets the salt water of the Pacific, providing an extraordinary range of habitats. Ecologists have long recognized ecotones as places of high biodiversity and great fertility. Other examples include wetlands where tidal waters flow in and out of marshlands and where forests open up to meadows. An ecotone is a soft overlapping of very different ecologies. Ecotones are
highly permeable; they are the opposite of a hard edge or boundary which presents a barrier to the flow of resources, energy, or information. Ecotones apply both to natural systems as well as human social diversity. Most design ignores ecotones. City planning practice as it developed in the early twentieth century emphasized zoning new development into single use land zones for housing, industry, commerce, and recreation. The older, more organic concept of mixed uses in close proximity was discouraged. Architects focused on creating new prototypes of single use buildings which inevitably neglected edges and interfaces with other systems both natural and human. Architects are still designing the “it” and seldom the edge, even though it is at the edges or ecotones where exchanges and interactions take place. Planning and development favor clear separation between land uses, while the automobile eats ecotones and turns them into dead zones. Thus we are left with the sterile empty plazas, parking lots, and highway edges of much new development. The designed ecotone can promote contact between people and natural systems. Other ecotones are simply accidental, or occur organically. The “town-gown” edge where campuses meet the local community is one example. Grandiose urban renewal schemes often sweep away such vibrant places. Designers could study three carefully cultivated ecotones that have evolved over millennia: the garden, the village, and the diversified family farm. Each incorporates a complex set of interfaces between people and nature. These forms have been around so long and have worked so well as ecological designs that they can continue to teach integral designers.