The Colorado Gap Analysis Project (CO-GAP) was initiated in 1991 as a cooperative effort, led by the Colorado Division of Wildlife in collaboration with the Natural Resource Ecology Center (NERC/USFWS), and state, federal, and private natural resources groups in Colorado.
Objectives of the Study
There are five major objectives of a GAP Project:
Land cover mapping
With funding from National Gap offices, 12 scenes of Landsat imagery were acquired to augment 4 Division of Wildlife scenes; providing a complete, in-house, statewide coverage with which a statewide baseline map of vegetation/land cover was developed at sufficient detail to model vertebrate wildlife distributions based upon habitat relationships. Following methodology developed for Wyoming Gap (WY-GAP), attributes were assigned to each polygon describing primary, secondary, and other land cover; crown closure for forested primary types; and the types of wetlands and/or disturbance found in the polygon, if any. Polygon attributes were assigned using image interpretation, existing maps, field reconnaissance, digital reference layers from Federal land management agencies, and literature sources. Formal state-wide validation of the land cover map is being performed as a separate task in conjunction with the Wyoming Gap Analysis project.
Species distribution mapping
Individual distributions for 597 vertebrate species were predicted using habitat associations linked to the vegetation/land cover base-layer, constrained by data on elevation ranges and confinements to the east or west side of the Continental Divide from known occurrences of individual species in Colorado. Point localities, and thematic distribution maps were used to evaluate preliminary distribution maps, and later as a guide in developing the county-level distribution masks used to constrain occupancy to likely areas of predicted habitat. County-level masks were developed by cross-reference to locational databases providing field/museum records of species localities. After synthesizing this information for modeling efforts, the modeled maps, predicting species range based on habitats were reviewed by local experts. A special submodel was developed to account for riparian species distribution, given the importance of this habitat and the minor extent to which it was observable based solely on the Landsat imagery.
Land Stewardship mapping
The Gap Analysis Program (GAP) uses a scale of 1 through 4 to denote the relative degree of management for biodiversity maintenance for a particular tract of land, where "1" represent the highest, most permanent and comprehensive level of maintenance, and "4" represents the lowest, or unknown status. Status codes were assigned to public lands with state and federal agency input based on legal and intended management, using a key developed by the New Mexico Gap Analysis Project (NM-GAP). Most private lands were assigned status 3 or 4 depending on the availability of information on their intended long-term management. Land Stewardship is derived from land ownership (Click on land ownership to view a map of Colorado Land Ownership.).
The final output
After land stewardship was modeled using the land status base layer, the derived layer was overlain on the vertebrate species habitat/distributions to provide the tabular output essential to a Gap Analysis of Colorado biodiversity. These tables provide listings to show the distribution of species habitats, across the major land ownership categories, and are further partitioned by hectares (and %) of the species habitat distributed by the land stewardship categories. Land cover types, and vertebrate species were generally considered under-represented in areas managed for biological diversity if less than 1%, or less than 50,000 hectares of available cover type, or occupied habitat was found within status 1 and 2 lands.
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Page last updated Wednesday July 18, 2001
By Colorado Division of Wildlife