Combined Habitat Assessment Protocols (CHAP)

Welcome to the Combined Habitat Assessment Protocols (CHAP)

CHAP is an accounting tool that uses spatially explicit methodology to measure habitat quality (including aquatic habitats) by evaluating biodiversity and their functions within a habitat type and/or structural condition. It has been applied in the Western United States with its origin in transportation project mitigation. It was developed in collaboration with 11 resource agencies that include: U.S. Army Corps of Engineers, Bureau of Land Management, Oregon Department of Environmental Quality, Oregon Department of Fish and Wildlife, Oregon Department of State Lands, Federal Highway Administration, NOAA Fisheries Service, State Historic Preservation Office, Environmental Protection Agency, U.S. Forest Service, and U.S. Fish & Wildlife Service.


CHAP is a spatially explicit tool that ranks different management alternatives for a site based on habitat units. It was originally developed for mitigation banking but it is equally well suited for determining baseline condition, evaluating habitat restoration options, and comparing conservation alternatives to baseline. It is based on the premise that higher functional redundancy is directly related to higher resiliency. CHAP evaluates hundreds of species, habitat components, and ecological function concurrently to produce functional redundancy values as an indicator of the overall ecological integrity of the site. CHAP provides an explicit and repeatable approach to evaluating functional patterns of species and communities, and the potential influences of management activities. Thus, CHAP can deliver an assessment of both impacts and enhancements that can be used in the planning and regulatory process.

CHAP maps an area or site by delineating polygons based on their habitat type and structural condition. State and regional peer-reviewed species maps are used to determine an initial list of vertebrate species. This list is reviewed by local state, federal, tribal and other interested stakeholders for appropriateness. Species that have the potential to be present are then linked to relevant habitat types associated with the site. This produces a presence/absence species list for the site.

Field inventories are used to confirm the presence of habitat types on the site and determine structural conditions and key environmental correlates, which are fine-scale habitat elements, for each map polygon. Field inventories also include percent species composition of invasive plants because of invasive species’ ability to reduce diversity and exclude native species from an area.

Functional-per-acre value scores are then calculated for each polygon based on existing habitat types and elements, called key environmental correlates that support species’ ecological functions. Scores for polygons with invasive species are discounted based on the percent composition.

CHAP is designed to work with information that is readily available in western states in particular, although it can be adapted for other regions of the country. It focuses on terrestrial vertebrates for scoring, as range data for terrestrial vertebrate taxa are most complete of all taxonomic groups. It does not require exhaustive site inventories of species composition or abundance, because restoration and mitigation banking is habitat based. If abundance information is available, particularly for a species of particular management concern such as a listed species, it can be included in the CHAP framework, however. CHAP is also designed to err on the side of inclusion of ecological functions for a site that may not be present rather than omitting those that likely are present.

Currently, CHAP does not include nutrient cycling relationships or disease vector ecology relationships. It does not incorporate nonlinear relationships among species. It is not designed or intended to quantify the total frequency, rate or abundance of ecological functional activities such as the total number of seeds dispersed per unit time, or unit area summed over all individual organisms performing this function.

To give you an example of this approach to follow is a series of projects whereby the CHAP metric, Functional Redundancy Value, was developed and used for a variety of assessments. These examples are group under a principal purpose for developing the information.


CHAP Overview


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