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Defining Restoration Goals 11110 BIOLOGY endangered species 1 endangered communities GEOGRAPHY Landscape ecology watersheds ecosystem management RESTORATION ECOLOGY WETLAND MANAGEMENT ecosystem functions 1 ecosystem services REVEGETATIONIREHABILITATION OF EXTREMELY DISTURBED LANDS vegetative cover "natural" community Figure 1. The separate strands contributing to the develop- ment of restoration ecology. Developments within each strand have contributed to the complexity of the field. Another historical base within restoration ecology comes from the disciplines of geography and landscape ecology. Practitioners in these fields look at entire land- scapes (Zonneveld 1995; Aronson & Le Floc'h 1996; Heathcote 1998; Naveh 1998), often using watersheds as the unit of restoration. This approach is at the opposite extreme of ecological organization from the species - centered approach, and reflects its origin in disciplines that have rarely involved studies of individual species. 410,, dscape -scale goals derive, in part, from the long his - in Europe of landscape management. Recently, the ecosystem /landscape approach has been incorporated into the idea of ecosystem management (Grumbine 1994; Vogt et al. 1997) and is the most commonly cited ideal for setting restoration goals. Wetland restoration represents a third, separate lin- eage within the discipline of restoration ecology. The practice of wetland restoration and creation developed independently of the above two strands, and was driven, to a large extent, by legislative mandates for the mitigation of damage to wetlands by economic devel- opment and by agriculture. These laws, in turn, were driven by the perception that many of the ecological processes that take place in wetlands are of value to so- ciety; wetland mitigation, thus, became an effort to re- place those processes and values. Although the percep- tion of ecosystem services performed more broadly by all ecosystems was a quasi - independent development (de Groot 1992; Costanza et al. 1997), the concept has been most extensively developed within the arena of wetland management as the perceived value of ecologi- cal processes within wetlands became widely recog- nized (Anonymous 1995; Zedler et al. 1998). Ecosystem services now are incorporated extensively in wetland management programs, in which "functional replace - Ont" is the explicit goal of laws and regulations. A fourth, independent strand in the braided structure of restoration ecology is the long history of attempting to manage the extreme, often toxic, results of resource extraction. An extensive literature has developed, de- scribing methods for reestablishing some semblance of a functioning ecosystem on spoils, mine pits, overbur- dens, salinized or highly eroded soils, etc. (Lal & Stew- art 1992; Munshower 1994). Restorationists working on such projects often do not pretend to create replicas of the ecosystems that were originally on the site; rather, the goal is usually to establish a functional ecosystem. The disparate historical roots of restoration ecology are apparent in the diversity of implicit and explicit goals of restoration efforts. In order to see how restorations are ori- ented in current work, I surveyed nearly 100 articles pub- lished during the past three years in Restoration Ecology. About 25% of the papers described projects whose pur- poses were to restore species, whereas 30% addressed the restoration of ecosystems, watersheds or landscapes, with little or no attention to individual species. The remaining 45% were concerned with a variety of goals addressing the restoration of particular assemblages of species, or levels of diversity, or sets of biotic interactions. Approximately 15% of the projects involved extremely disturbed condi- tions, including mine sites, waste sites, gravel pits, and roadsides; 18% were concerned with wetland restoration and creation. The rest were more or less evenly divided among forest, aquatic, grassland /prairie, and other types of ecosystems. In a special issue on riparian restoration (Restoration Ecology, Volume 5(4), 1997), the majority of au- thors discussed landscape -level criteria for setting goals and priorities. Thus, recent practice in restoration ecology continues to reflect, in its published results, the variety of historical sources for the field. Restoration of Species The restoration of species is predicated on an under- standing of the autecology and habitat requirements of the species of concern. Common foci for research include the genetic structure of populations and metapopula- tions, population biology, minimum viable population size, issues of local adaptedness, and the kinds of inter - specific interactions (predators, prey, mutualists, com- petitors) that may be important in establishing or main- taining populations. The advantages of species- centered restoration are clear (Table 1): species threatened by extinction are res- cued, or at least given a better chance of survival. The recent delisting of several endangered species testifies to the importance and possible success of this approach. There are several problems, however, that may be associ- ated with attempts to restore individual species (Table 1). First, the definition of a species' habitat, which is an es- sential, primary step in defining conditions for both conservation and restoration, can involve implicit, un- recognized knowledge of ecosystem- or landscape -level interactions and processes. Failure to understand. the 3 MARCH 2000 Restoration Ecology