SDCP desert scene  - Illustration by Bill Singleton
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A Vision for Biological Corridors and Critical Habitat

The work on the biological corridors and critical habitat element of the Sonoran Desert Conservation Plan revealed that biology is the basis for all other elements. The strong interconnections of all five elements are critical in forming a viable land management plan that ensures continuing biodiversity for Pima County.

Roadrunner desert scene  - Illustration by Bill Singleton & George Maleski

Biological Corridors and Critical Habitat

Pima County is committed to the long-term survival of the full spectrum of
indigenous plants and animals and the conservation of its cultural resources.

The two elements that most directly express the biological basis of Pima County, Arizona’s Sonoran Desert Conservation Plan are biological corridors and critical and sensitive habitats.
When the Plan began in 1998, the science community did not have a list of priority vulnerable species of concern, a set of biological standards, or even a vegetation map that could serve as the starting point for determining the locations in need of protection for the species that are in decline.
After an intensive research effort involving dozens of members of both the local and national science community much has been achieved. A list of potentially covered species has been identified, the best available vegetation maps are now assembled, and the science community has identify the patches of habitat and connecting corridors that will establish an effective and lasting biological reserve.
For the nine mammals, eight birds, seven reptiles, seven plants, six fish, two amphibians, and numerous invertebrates that have been identified thus far as being in need of protection, the biological goals of the plan will be of great assistance in promoting recovery and improving the status of these species.
This is true not only because a statement of biological goals and objectives has been articulated, but because we are now able to gather information in a comprehensive fashion, take actions to improve the status of the species in the short term, and craft an adaptive management plan that continues to improve the information base and the conservation program over the long term. Substantial contributions from the expert community have also built the Critical Habitat and Biological Corridors Elements.
Sonoran Desert Ecoregion Plan
The Nature Conservancy’s prestigious ecoregional plan for the Sonoran Desert has been published and adopted by the Science Team. Dr. Gary Nabhan’s influential work on the ironwood tree led to the creation of the Ironwood National Monument. The ecosystem of the Sonoran Desert is one of the most important places on
earth, deserving of special attention and protection.

Biological Corridors
When the conservation plan was initiated, the scientific community had little data collected about the interaction of land development and the decline of biodiversity. Three years later, a scientific basis has been established that exceeds the precision of other national conservation plans, and represents the start of long-term investment in research, monitoring and adaptive management. In addition, critical habitat designations identify unique Sonoran Desert habitat associations, not previously recognized, promoting sustained Sonoran Desert bio-diversity. While the flower of the protected saguaro cactus is the state flower, science has proven that the unprotected ironwood tree is really the tree of life for the Sonoran Desert.

Ironwood Flowers - Illustration by Bill Singleton

Critical Riparian Habitats
The majority of the priority vulnerable species in Pima County are associated with aquatic and riparian-based ecosystems. This list of species also points out the importance of other landscape elements or features that are also threatened in Pima County. Grasslands, desert scrub, caves, adits and talus slopes serve as unique habitat niches that support vulnerable species.

A Full Spectrum of Biodiversity
Protecting indigenous species requires more than conserving the habitat of individual species. Maintaining the full spectrum of native biodiversity requires the inclusion of vegetation communities when assembling a viable reserve system. Attention must also be paid to larger ecological processes. Many areas vital to the survival of vulnerable species may be outside of, or corridors between, existing parks or natural preserves.
Identification of Vulnerable Species
Under the direction of the Science Technical Advisory Team, a list of the most vulnerable plant and wildlife species was developed. This began with an initial list of over one hundred species recognized as imperiled, species extirpated from Pima County, and additional species in decline or in jeopardy. This review resulted in a short list of 55 species that were identified by the Team as priority vulnerable species, warranting further analysis, consideration, and conservation.

Priority Habitats and Corridors
The selected Priority Habitats and Corridors include:
• Altar Valley
• Baboquivari Mountains
• Cienega Creek
• Eastern Tucson Riparian Complex
• Organ Pipe/Goldwater Complex
• Sabino Canyon
• San Pedro River
• Santa Rita Mountains
• Silverbell Mountains
• Tortolita Mountains
• Tucson Mountains

Evaluation Process
The collection and synthesis of biological data has been ongoing in Pima County for decades. Records date back to the 1800s and extend into present time to reflect agency, academic, and private sector efforts. This information provides a broad historical context for examining existing conditions.
The Pima County Board of Supervisors appointed the Scientific Technical Advisory Team to develop the biological resources element of the Sonoran Desert Conservation Plan. In May, 1999, this multi-agency, multi-disciplinary team met to begin discussions about the biological underpinnings for a regional conservation plan. Since that time they and County staff, along with consultants, biologists, and natural resource managers, have identified the plant and wildlife species of greatest concern.
Numerous studies were prepared by experts in the fields of biology and water resources including important new data published for the first time. Pima County’s superlative geographic information system was used to analyze information in ways that have never before been possible. An extensive GIS mapping database was compiled and numerous illustrations and diagrams were created. The information was then released to the public for additional input and review.


Conservation Stategies
Focus future growth and associated infrastructure expansion in areas in closest proximity to existing urbanized areas, not in areas of highest biological richness.
Significantly lower intensity of future land uses allowed in certain biologically sensitive areas near major washes, within ecologically rich habitats, adjacent to Saguaro National Park, and other sensitive areas of Pima County.
Avoid or minimize future losses and fragmentation by a publicly supported land acquisition and conservation program. Open Space Acquisition funds and other private/public partnerships enable the acquisition of lands or conservation easements adjacent to the existing reserve system as well as ranches conserved through acquisition of development rights or conservation easements, thereby implementing the Ranch Conservation and Mountain Park Expansion Elements of the SDCP.
Prioritize 26 percent of the CLS for conservation by the adoption of Habitat Protection Priorities in Eastern Pima County. This includes approximately 525,000 acres of biological core, important riparian areas, threatened and endangered species management areas, and special landscape elements.
Pima County will continue to nominate and pursue acquisition of biologically sensitive lands for reclassification by the Arizona State Land Department under the Arizona Preserve Initiative, or through state land constitutional reform.
Conserving important biological resources has become a very important part of future land use decisions.


Biological Corridors and Critical Habitat Map (PDF)



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Tucson, AZ 85701


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