Date:March 20, 1996
Series:Population and Habitat Evaluation Methods
Part 870: Habitat Assessment
Originating Office: Division of Habitat Conservation
1.1 Purpose. The purpose of this chapter is to provide policy, standards, and guidance for application of the Habitat Evaluation Procedures (HEP) in the Fish and Wildlife Service.
1.2 Objectives. The application of HEP will implement standardized procedures for evaluating project impacts, on both terrestrial and inland aquatic habitats, and for comparing alternative plans or projects.
1.3 Description. HEP is a habitat-based approach for assessing environmental impacts of proposed water and land resource development projects. The method can be used to document the quality and quantity of available habitat for selected wildlife species. The procedures provide information for two general types of wildlife habitat comparisons: the relative value of different areas at the same point in time; and the relative value of the same areas at future points in time. By combining the two types of comparisons, the impact of proposed or anticipated land and water use changes on wildlife habitat can be quantified.
1.4 Application. HEP may be used to assess impacts of Federal water and land resource projects or programs, as required by the Fish and Wildlife Coordination Act such as projects conducted by the U.S. Army Corps of Engineers or the Bureau of Reclamation, or licensed by the Federal Energy Regulatory Commission; as well as planning studies of the Natural Resources Conservation Service, Bureau of Land Management, and U.S. Forest Service. In addition, HEP can be applied to the planning activities of Federal agencies, particularly when the Service is involved as a cooperating agency under the Council on Environmental Quality's Regulations for implementing the National Environmental Policy Act.
A. The Assistant Director - Ecological Services establishes HEP policy, standards, and guidance. The Assistant Director is assisted by the Division of Habitat Conservation which considers all comments concerning effectiveness of policy and standards for meeting objectives and recommends or makes appropriate changes through the Assistant Director.
B. Regional Directors are, where appropriate, responsible for utilizing HEP in accordance with the provisions of this chapter.
1.6 The Habitat Evaluation Procedures.
A. HEP was developed in 1980 in response to the need to document the nonmonetary value of fish and wildlife resources. HEP evolved from an assessment method developed in Missouri (Daniels and Lamaire 1974) and is based on the fundamental assumption that habitat quality and quantity can be numerically described. Numerical description permits options and alternatives to be compared when numerical changes are the essence of impact assessment.
B. HEP is a species-habitat approach to impact assessment; and habitat quality for selected evaluation species is documented with an index, the Habitat Suitability Index (HSI). This value is derived from an evaluation of the ability of key habitat components to supply the life requisites of selected species of fish and wildlife. Evaluation involves using the same key habitat components to compare existing habitat conditions and optimum habitat conditions for the species of interest. Optimum conditions are those associated with the highest potential densities of the species within a defined area. The HSI value obtained from this comparison thus becomes an index to carrying capacity for that species.
C. The index ranges from 0.0 to 1.0, and for operational purposes in HEP, each increment of change must be identical to any other. For example, a change in HSI from 0.1 to 0.2 must represent the same magnitude of change as a change from 0.2 to 0.3, and so forth. Therefore, HSI must be linearly related to carrying capacity. This is an operational restriction imposed by the use of HSI in HEP. However, it is a restriction easily complied with; if the relationship between HSI and carrying capacity is unknown, it is assumed to be linear. If the relationship is nonlinear, it is converted to a linear function.
D. HEP attempts to incorporate concepts from both the population and habitat theories by evaluating habitat quality for specific species. HSI values are obtained for individual species through use of documented habitat suitability models employing measurable key habitat variables (e.g., percent canopy closure). The HSI values are multiplied by area of available habitat to obtain Habitat Units (HU's) for individual species. These values are used in the HEP system for comparative purposes. No aggregation of species' HSI (or HU's) occurs.
E. Many potential users tend to consider the HSI value as synonymous with the entire HEP system. This is not the case. HEP can be compared to a bookkeeping ledger; both passively display and document values obtained from other sources. HEP is a data management system; it is the data it manages, i.e., the index of quality and the quantity of available habitat, which are of interest in impact assessment.
1.7 Attributes and Limitations of the HEP.
A. Various forms are used in HEP to display and document HSI, area, and HU's for each evaluation species. Comparisons can be made either between two areas at one point in time, or for one area for several points in time, for any proposed action. However, the ability to document data and ultimately compare alternatives is not unique to the HEP system.
B. The differences in quality (HSI) and quantity (area) between existing habitat conditions (baseline) and various projected future sets of conditions document project-related impacts for selected evaluation species. HEP currently does not provide guidance for performing future projections; therefore, projected impacts are no better than the user's ability to predict future conditions.
C. HEP can be applied at any level of assessment. However, data requirements and costs increase as more species are considered and their respective habitat models become more complex. HSI models not only provide an index value of quality, but also document which habitat variables were considered and their respective values. The level of detail for such "models" must fit the user's objectives for impact assessment.
D. The identification of differing types and magnitudes of impacts is dependent on the validity and sensitivity of the HSI models used to generate data for HEP. As with other approaches, the results of an impact assessment employing HEP are no better than the reliability of resource data used.
E. HU's serve not only as the principal units of comparison in HEP, but also as a standard vehicle of communication, integrating both quality and quantity of habitat. Changes in HU's represent potential impacts from proposed actions. Such changes are annualized in order to be comparable with the action agencies' benefit/cost analyses. Applications of annualized HU's include impact assessments, compensation studies, and human use analyses. In such analyses, one HU lost for a species must be directly comparable to one HU gained for that species. The latter association explains the requirement for a linear relationship between HSI and carrying capacity.
F. HEP is a species-based assessment methodology. It is applicable only for the species evaluated and does not directly relate that species with other ecosystem components. HEP conceptually addresses only the issues of species populations and habitat. However, the degree to which these indicators are addressed by HEP is dictated by the HSI models. Through improved HSI models, it may be possible to more completely treat the remaining issues of biological integrity and environmental values.
G. In summary, the HU data developed are the essence of the HEP methodology. The identified changes in habitat quality and quantity provide the basis for biologists to compare alternatives for the evaluation species selected. HEP is a convenient means of documenting and displaying, in standard units, the predicted effects of proposed actions. It is a tool available to resource managers who must make knowledgeable decisions.
1.8 Conduct of Evaluations.
A. General. The HEP may be used as a basic tool for evaluating project impacts on fish and wildlife resources and as a basis for formulating subsequent recommendations for mitigation, including fish and wildlife resources management planning, except for cases where:
(1) Time constraints are such that applying HEP would not be possible;
(2) Adequate funds (transfer or otherwise) are not available;
(3) The project size or impacts are expected to be relatively insignificant; or
(4) The project is not deemed appropriate for application of HEP.
B. Interdisciplinary Planning Teams. Maximum effort will be made to conduct HEP evaluations using interdisciplinary planning teams consisting of biologists from the Service, the Federal action agency, the appropriate State fish and wildlife agency, and any other affected agency or party.
C. Secondary Impacts. In reviewing projects or other proposals, and whenever practicable, the planning team will evaluate the total impact of the development, including any part located on uplands and any secondary fish and wildlife impacts.
D. Endangered/Threatened Species. The consideration of endangered and threatened species in project planning is required by Section 7 of the Endangered Species Act of 1973, as amended, and related regulations. Thus, to avoid any possibility of confusion with the consultation requirements of Section 7 of the Endangered Species Act, no federally-listed endangered or threatened species should be used as an evaluation species in a HEP study.
E. Documentation. Each HEP will include documentation of study objectives, assumptions, level of acceptance for Habitat Suitability Index (HSI) models and compensation objectives and goals, as appropriate. This documentation will be included as an integral part of any FWCA report based on a HEP evaluation.
A. The HEP handbook is issued by the Assistant Director - Ecological Services. It contains specific and detailed guidance on applying and implementing HEP, and consists of three chapters:
Habitat as a Basis for Environmental Assessment (formerly 101 ESM) September, 15, 1980.
Habitat Evaluation Procedures (formerly 102 ESM) March 31, 1980.
Standards for the Development of Habitat Suitability Index Models (formerly 103 ESM) April 10, 1981.
For additional information about this policy, contact the Division of Habitat Conservation. For more information regarding this Web page, contact Krista Holloway, in the Division of Policy and Directives Management.