Restoration ecology has been described as "the full or partial replacement of structural or functional characteristics that have been extinguished or diminished and the substitution of alternative qualities or characteristics than the ones originally present with the proviso that they have more social, economic, or ecological value than existed in the disturbed or displaced state" (Cairns, 1988b). Several restoration fields have developed somewhat independently, and all appear to have the design of ecosystems as their theme. Although related to ecological engineering or even a part of it, several of these approaches seem to lack one of the two major criteria of ecological engineering, namely (1) recognizing the self-designing ability of ecosystems or (2) basing the approaches on a theoretical base, not just empiricism. Early work in Europe was based on the concept of bioengineering, the use of plants as engineering materials (Schiechtl, 1980). More recently, much has been written on restoration ecology (Aber and Jordan, 1985; Buckley, 1989; Jordan et al., 1987) and ecosystem rehabilitation (Cairns, 1988a; Wali, 1992). This approach has also been applied to river and stream restoration (Gore, 1985) and to agriculture as agroecosystems (Lowrance et al., 1984).
Ecological engineering, or ecotechnology, involves several approaches or applications to the design of landscapes (Table 1). These applications range from constructing new ecosystems for solving environmental problems to ecologically sound harvesting of existing ecosystems.
Early development of ecological engineering in the West has stressed a partnership with nature and has been investigated primarily in experimental ecosystems rather than in full-scale applications. Some of the more significant experiments that have been conducted or are currently under way in ecological engineering relate to aquatic systems, particularly shallow ponds and wetlands. Ecological engineering as practiced in China has been applied to a wide variety of natural resource and environmental problems, ranging from fisheries and agriculture to wastewater control and coastline protection. The emphasis in the Chinese systems has been on applications rather than experimentation and on the production of food and fiber more than environmental protection (Mitsch, 1991; Mitsch et al., 1993b). To simplify the variety of approaches and systems used in ecological engineering, Mitsch (1993) divided ecological engineering case studies into three categories: