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Twenty-Third Annual Meeting and Symposium of the
Desert Tortoise Council, April 3-5, 1998
Abstracts
Status of the Northern & Eastern Colorado Desert Coordinated Management Plan
Richard E. Crowe
Bureau of Land Management, California Desert District, 6221 Box Springs Blvd., Riverside, CA
92507-0714
One of three ecosystem plans in progress that address the recovery of the desert tortoise in the California Desert, the Northern & Eastern Colorado Desert Coordinated Management Plan (Plan) focuses on the Northern and Eastern Colorado Desert Recovery Units and a small portion of the Joshua Tree Recovery Unit. The planning area, 5.5 million acres in size and lying in the Sonoran Desert Ecoregion, is bounded by I-40 (north), the Colorado River (east), the Imperial Sand Dunes and Coachella Canal ( south), and the West Mojave Plan (west). The planning area does not have urbanization pressures which characterize other parts of the California Desert. The major cooperating agencies are the Bureau of Land Management (lead agency), Joshua Tree National Park, U.S. Marine Corps Air Station in Yuma for the Chocolate Mountains Gunnery Range, U.S. Fish & Wildlife Service, and California Department of Fish & Game (which has provided the lead wildlife biologist). Additional cooperators to the Plan include other Federal, state, and local agencies as well as many interest groups. Plan scope is ecosystem comprehensive. Plan decisions will amend existing land use plans of the cooperating Federal agencies for the tortoise and other species and habitats and may be of use by other agencies and companies with interests in the planning area.
Work on the Plan in the last year was focused on completing the collection of data and the mapping of plant communities. The latter included an accuracy assessment, collection of additional habitat data for species-habitat modeling, and correcting the map with the accuracy information. From the accuracy assessment exercise we found plant communities to be accurate to varying degrees with an overall accuracy of about 50%. Plant communities and overall map accuracy after corrections were made is greatly improved. All spatial data has been GIS digitized to aid in modeling, analyses, and Plan development.
Species-habitat-ecological processes models are currently being run. They will help define and map areas of relative biodiversity importance. The California Wildlife-Habitat Relationship System (WHR), developed by the California Resources Agency, is the modeling technique employed. It has been tailored to the particular species and habitats found in the planning area. Modeling results will be used in analyzing use biodiversity conflicts and aid Plan development. Model maps will be completed prior to April, 1998. The basis for modeling is plant communities and includes natural and artificial water sources, species accounts and known occurrence of wildlife and plant species of concern, habitat data collected during the accuracy assessment noted above, detailed information on the desert tortoise and bighorn sheep, a characterization of the important ecological processes, and various physical features. Physical features data available include elevation, slope, aspect, landforms, and lithology. Criteria for assigning relative biodiversity value to habitats have been developed for species uniqueness, rarity, or range limits; ecological processes; habitat fragmentation; species richness/diversity; and exotics. A different modeling protocol was developed to predict the occurrence of rare plants. It is based on a limited set of considerations: elevation range, plant community, landform and distance from known occurrences of the same species.
Major scheduled milestones for remaining work on the Plan are as follows:
April, 1998 - Complete value and conflict analyses; develop Plan and decisions
August, 1998 - Issue draft Plan/EIS; 90-day public review
February, 1999 - Issue Proposed Plan/EIS; 30-day public review
April, 1999 - Sign Record of Decision
The Plan lead, Dick Crowe, may be contacted for further information at the above address and by calling (951) 697-5216.
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