Background and Purpose
The Southwest Regional Gap
Analysis Project predicted habitat for 819 vertebrate species
that reside, breed, or use habitat in the five-state region for a
substantial portion of the their life history. The list of species
to model was determined by identifying decision rules for taxon
inclusion (These rules can be provided upon request). To create the
most accurate models possible we are engaging taxa experts to
provide a review of these habitat models.
These models are based on the
concept of Wildlife Habitat Relationships (WHRs). We have defined
WHRs as a statement describing resources and conditions present in
areas where a species persists and reproduces or otherwise occurs.
Relationships can be modeled to predict habitat composition, and if
the relationships are represented in a cartographic plane they can
predict the presence of habitat spatially. For each species, these
relationships were identified by reviewing the available literature
and then generating a spatial representation of habitat within the
species known range.
An important factor for model
implementation is understanding the objectives of the modeling
effort and the assumptions of the models. The objective of the
habitat models are to: 1) Provide maps that predict the distribution
of terrestrial vertebrate species in the project area to support
analysis of conservation status; and 2) Develop a database of
geographic range, wildlife habitat relationships, and predicted
distribution of each vertebrate species for the long-term utility of
GAP and its cooperators (Csuti and Crist 2000). Along with these
objectives are several assumptions associated with GAP vertebrate
habitat models (Csuti and Crist 1998):
are assumed to occur within a polygon representing potential habitat
but are not predicted to occur at any particular point within that
are assumed to be present within a polygon, but no assumptions are
made about the abundance of the species in the polygon.
are assumed to be present in a polygon at least once in the last 10
years but need not be present every year in the last decade.
are assumed to be present during some portion of their life history,
not necessarily during the entire year.
There are many challenges to
creating habitat maps. GAP uses expert review and a measure of
agreement method in an effort to create the most accurate models
possible. This document describes the expert review process within
model review from knowledgeable individuals on the modeled
terrestrial vertebrates across the five-state region.
The SWReGAP habitat models have three
model components for review. These are: 1),
Wildlife habitat relationships (Report), 2) range extent and coding
(Range); and 3) spatial depiction of predicted habitat (Model).
Review of this section will either
substantiate or refute the habitat relationships used in the model.
This process should include 1) review of each relationship used in
the model, 2) concurrence with the relationships; and 3) review of
references to ensure that important citations are not missed.
Questions to focus on this part of the review include:
the habitat relationships (within the limits of available
information) correctly identified?
there additional relationships not identified, which should be
included? Knowledge regarding
the limitations of the habitat relationships are also requested.
The second component for the review is
to ensure that the range extent accurately depicts the known range
of the species. The review should include an evaluation of: 1)
extent, and 2) coding (this section is most relevant to migratory
taxa, e.g., permanent resident, summer breeder). Some
the range extent, as depicted by hydrologic units, reflect the known
range of species?
the hydrologic units correctly coded?
Review of map depiction is a
subjective review based on expert knowledge. The review of this
tier should focus on the following questions:
Does the depiction look
Does the depiction identify too
Does the depiction not identify
Does the habitat identified
appear to be spatially correct?
be identified based on a reference with associated source code
allow information to be regionally applied except in special
cases. Special cases include species that have specific and
relatively well-known habitat associations that can be
represented in separate reasonably well-informed models.
Table 1. Categories of reference
is based on substantive direct investigation and published
(printed or electronic) in an outlet subject to peer
is based on direct investigation or general review and is
available in any of a variety of general publications that
are serial or ad hoc documents of a technical nature subject
to uncertain degree of professional review.
is derived directly or indirectly from individuals with
demonstrated limited or broad expert credence; formats
include but are not limited to word-of-mouth accounts, field
journals, specimen record tags or forms, labeled
is inferred from associations applicable to similar taxa.
* Though not a preferred reference,
because of taxonomy changes this option may be applicable.
Csuti, B. and P. Crist. 1998. Methods for Assessing
Accuracy of Animal Distribution Maps, Gap Analysis Program,
University of Idaho, Moscow, Idaho. http://www.gap.uidaho.edu/
Date Accessed: 02 July 2003.