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Water: Restoration

Definitions & Distinctions

What is Restoration?


Ecological restoration is a valuable endeavor that has proven very difficult to define. The term indicates that degraded and destroyed natural wetland systems will be reestablished to sites where they once existed. But, what wetland ecosystems are we talking about? How far back in time should we go to find target ecosystems? Is establishing any type of wetland enough to be called "restoration"?

Restorationists have considered these questions at length and addressed them in the current definitions of restoration and restoration-type activities. Several of these definitions are discussed in the sections below. A simple and useful definition of restoration was developed by the National Research Council (NRC). In its 1992 report, Restoration of Aquatic Ecosystems, NRC defined restoration as the "return of an ecosystem to a close approximation of its condition prior to disturbance." The concept of restoration is further clarified by defining many types of restoration-related activities. These activities, such as creation, reallocation, and enhancement, are similar to restoration, but differ in some way from the process of renewing native ecosystems to sites where they once existed.

Definitions for these terms have often been developed from an ecological perspective and some of these are given in the section below, Definitions from the restoration literature. Recently, several federal agencies agreed on refined versions of the ecologically-based definitions in order to help them implement public policy. In particular, these definitions are designed to help agencies accurately track wetland losses and gains across the nation. These agency-developed definitions are given below in the section, Federal Agency Definitions for Wetland Tracking.

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leafDefinitions from the Restoration Literature

What is Restoration?

The National Research Council (NRC) Exit EPA Disclaimer, in its 1992 report, Restoration of Aquatic Ecosystems, defined restoration as the "return of an ecosystem to a close approximation of its condition prior to disturbance." That report also states, "The term restoration means the reestablishment of predisturbance aquatic functions and related physical, chemical and biological characteristics (Cairns, 1988; Magnuson et. al., 1980; Lewis, 1989). Restoration is &hellips; a holistic process not achieved through the isolated manipulation of individual elements.

The holistic nature of restoration, including the reintroduction of animals, needs to be emphasized &hellips; Merely recreating a form without the functions, or the functions in an artificial configuration bearing little resemblance to a natural form, does not constitute restoration. The objective is to emulate a natural, self-regulating system that is integrated ecologically with the landscape in which it occurs. Often, restoration requires one or more of the following processes: reconstruction of antecedent physical conditions, chemical adjustment of the soil and water; and biological manipulation, including the reintroduction of absent native flora and fauna&hellips;"

The NRC report also advises: "Without an active and ambitious program in the United States, our swelling population and its increasing stresses on aquatic ecosystems will certainly reduce the quality of human life for present and future generations. By embarking now on a major national aquatic ecosystem restoration program, the United States can set an example of aquatic resource stewardship that ultimately will also improve the management of other resource types and will set an international example of environmental leadership."

Gwin, et al. (1999) state that restoration requires knowledge of the wetland type prior to disturbance; restoration has the goal of returning the wetland to that type. However, Lewis (1989) notes that "it is not necessary to have complete knowledge of what those pre-existing conditions were; it is enough to know a wetland of whatever type was there and to have as a goal to return to that same wetland&hellips;it is not necessary that a system be returned to a pristine condition." He also finds that restoration may occur when a degraded wetland is returned to a previous condition of ecological functioning, although that previous condition may have also been altered by human activity.

The Society for Ecological Restoration (SER) Exit EPA Disclaimer includes sustainable cultural activities, such as those practiced by indigenous peoples, in its current definition of restoration. SER defines ecological restoration as "the process of assisting the recovery and management of ecological integrity. Ecological integrity includes a critical range of variability in biodiversity, ecological processes and structures, regional and historical context, and sustainable cultural practices."

There are also numerous restoration-related activities that differ in some important way from the definitions given above.

What is Creation?

Creation is the "construction of a wetland in an area that was not a wetland in the recent past (within the last 100-200 years) and that is isolated from existing wetlands (i.e., not directly adjacent)" (Gwin, et al., 1999). In other words, creation occurs when a wetland is placed on the landscape by some human activity on a non-wetland site (Lewis, 1989). Typically, a wetland is created by excavation of upland soils to elevations that will support the growth of wetland species through the establishment of an appropriate hydrology.

What is Enhancement?

Gwin, et al. (1999) define enhancement as "the modification of specific structural features of an existing wetland to increase one or more functions based on management objectives, typically done by modifying site elevations or the proportion of open water. Although this term implies gain or improvement, a positive change in one wetland function may negatively affect other wetland functions". Lewis (1989) also states that enhancement may also be the alteration of a site to produce conditions that did not previously exist in order to accentuate one or more values of a site. For example, increasing the area of deep water by excavating parts of an emergent wetland may provide more duck habitat (the desired wetland value), but may decrease foraging and cover habitat for young fish.

What is Reallocation or Replacement?

These terms apply to activities in which most or all of an existing wetland is converted to a different type of wetland. For example, changing an emergent wetland to a pond converts the habitat from one wetland type to something quite different.

What is Mitigation?

Mitigation, a term that frequently occurs in discussions of restoration, "refers to the restoration, creation, or enhancement of wetlands to compensate for permitted wetland losses" (Lewis, 1989). Under Section 404 of the Clean Water Act, wetlands may legally be destroyed, but their loss must be compensated for by the restoration, creation, or enhancement of other wetlands. In theory, this strategy should result in "no net loss" of wetlands. For a recent analysis of the effectiveness of wetland mitigation, see articles by J. Zedler (1996) and M. S. Race and M. S. Fonseca (1996) in the scientific journal, Ecological Applications.

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leafFederal Agency Definitions for Wetland Tracking


The Federal Geographic Data Committee, Wetlands Subcommittee, composed of several federal agencies, developed definitions for restoration and related activities designed to aid agencies in accurately reporting wetland increases due to their program activities. Many different definitions of these terms have been used by various agencies. The definitions, below, provide standard terminology for the more than 15 agencies involved in wetland restoration, related activities, and/or mitigation.

Restoration: the manipulation of the physical, chemical, or biological characteristics of a site with the goal of returning natural/historic functions to former or degraded wetland. For the purpose of tracking net gains in wetland acres, restoration is divided into:

  • Re-establishment: the manipulation of the physical, chemical, or biological characteristics of a site with the goal of returning natural/historic functions to a former wetland. Re-establishment results in rebuilding a former wetland and results in a gain in wetland acres.
  • Rehabilitation: the manipulation of the physical, chemical, or biological characteristics of a site with the goal of repairing natural/historic functions of degraded wetland. Rehabilitation results in a gain in wetland function, but does not result in a gain in wetland acres.

Establishment: the manipulation of the physical, chemical, or biological characteristics present to develop a wetland that did not previously exist on an upland or deepwater site. Establishment results in a gain in wetland acres.

Enhancement: the manipulation of the physical, chemical, or biological characteristics of a wetland (undisturbed or degraded) site the heighten, intensify, or improve specific function(s) or for a purpose such as water quality improvement, flood water retention or wildlife habitat. Enhancement results in a change in wetland function(s) and can lead to a decline in other wetland function, but does not result in a gain in wetland acres. This term includes activities commonly associated with the terms enhancement, management, manipulation, directed alteration.

Protection/Maintenance: the removal of a threat to, or preventing decline of, wetland conditions be an action in of near a wetland. Includes purchase of land or easement, repairing water control structures or fences, or structural protection such as repairing a barrier island. This term also includes activities commonly associated with the term preservation. Protection/Maintenance does not result in a gain of wetland acres or function.

Federal Geographic Data Committee Wetlands Subcommittee members

  • US Department of Interior
    • US Fish and Wildlife Service
    • Bureau of Land Management
    • National Park Service
    • US Geological Survey
    • Bureau of Reclamation
    • Office of Surface Mining
    • Bureau of Indian Affairs
  • US Department of Agriculture
    • Natural Resources Conservation Service
    • Forest Service
  • Environmental Protection Agency
  • National Marine Fisheries Service (NOAA)
  • National Aeronautical and Space Agency
  • Department of Energy
  • Tennessee Valley Authority
  • Army Corps of EngineersDepartment of the Army
  • US Marine Corps
  • US Navy
  • US Air Force
  • Office of Management and Budget
  • National Capital Planning Commission
  • Department of Housing and Urban Development


Gwin, S.E., M.E. Kentula, and P.W. Shaffer. 1999. Evaluating the Effects of Wetland Regulation through Hydrogeomorphic Classification and Landscape Profiles. Wetlands 19(3): 477-489.

Lewis, R. R. III 1989. Wetland restoration/creation/enhancement terminology: Suggestions for standardization. Wetland Creation and Restoration: The Status of the Science, Vol. II. EPA 600/3/89/038B. U.S. Environmental Protection Agency, Washington, D.C.

National Research Council. 1992. Restoration of Aquatic Ecosystems: Science, Technology and Public Policy. National Academy Press, Washington, D.C.

Race, M. S. and M. S. Fonseca. 1996. Fixing compensatory mitigation: What will it take? Ecological Applications 6(1):94-101.

Society for Ecological Restoration website Exit EPA Disclaimer

Zedler, J. 1996. Ecological issues in wetland mitigation: An introduction to the forum. Ecological Applications 6(1):33-37.

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