By Vanessa Bechtol, Arizona Open Land Trust

Growth rates across southern Arizona are skyrocketing at rates more than double the national average. Pima County's 10-year growth rate is 27 percent, compared to the national average of 13 percent. Urban encroachment, subdividing of rural parcels, and the ever-increasing presence of roads associated with these excessive growth rates threaten ecological resources and wildlife habitat throughout southern Arizona.

Large ranches are currently being subdivided into smaller lots for rural residential development. The ranches are frequently subdivided into ranch estates ranging from four to 40 acres in size. The subdivision of large rural parcels currently used for ranching threatens biological diversity and wildlife habitat linkages. Habitat linkages between the numerous mountain ranges of southern Arizona are crucial to wildlife survival. The subdivision of rural parcels will fragment the landscape and completely break habitat linkages, forcing wildlife into unsuitable habitat, thus threatening species survival.

To address these concerns, in 1998 Pima County began preparing a multispecies habitat conservation plan, the nationally acclaimed Sonoran Desert Conservation Plan (SDCP). As part of the planning process, the county published the Conservation Land System (CLS). CLS used scientific data and review by experts to identify more than two million acres of land as biological core or important riparian areas that merit protection under SDCP. The lands identified are considered by the SDCP's Science and Technical Advisory Team as the most viable locations to protect the county's vulnerable species.

Overwhelmed with the idea of protecting two million acres, the Arizona Open Land Trust, with its partner, The Nature Conservancy (TNC), took advantage of an opportunity to use GIS to refine CLS and identify lands that were most sensitive and should be prioritized for protection. Taking on the task of identifying conservation priorities was a natural role for the Trust, as it has worked for more than 25 years to protect southern Arizona's vanishing western landscapes and wildlife habitat.

The Trust and TNC prepared the Habitat Conservation Priorities for Eastern Pima County by analyzing available data from CLS and enhancing available county data with information from other expert sources. ArcView software allowed technical team members to ask and answer key spatial questions in real time. Initially, a model was built unioning landownership, land status, and CLS land layers. This model was used in an initial workshop to demonstrate to the Trust technical committee the relationship of CLS lands to the current ownership and management status of these lands. Over the course of the next 18 months and many additional workshops, the Trust technical committee evaluated hundreds of other original parcels and derived data layers to help select the most important parcels for preservation.

ArcView was chosen for its ease of use in quickly adding and displaying very large vector and raster data layers. A key to the project's success was the ability of the Trust technical committee members to ask and answer questions on the fly about various layers' attributes and the spatial relationship between these layers. ArcView was able to provide stakeholders with an intuitive spatial and attribute view of multiple data layers that informed their decision as to land acquisition priority.

The 18-month study to identify and prioritize lands with the highest conservation values in eastern Pima County used several dozen biological datasets to systematically evaluate CLS and ultimately mapped 100,000 acres of private land (43,000 of those acres as high priority) and 180,000 acres of state land for protection.

The Habitat Conservation Priorities map was adopted by both the Citizens' Steering Committee for the Sonoran Desert Conservation Plan and the Pima County Board of Supervisors as the focus of county conservation efforts. The Habitat Conservation Priorities for Eastern Pima County calls for protection of the community's richest biological resources on both private and state land by working with willing sellers. The Trust is partnering with Pima County to protect these lands in perpetuity by negotiating land acquisitions. Funding to acquire and protect the conservation priorities comes from the May 2004 Open Space Bond that raised $174.3 million for habitat conservation.

Since the adoption of the Habitat Protection Priorities map, the Trust has already assisted in the acquisition and permanent protection of 10,395 acres of high-priority conservation lands. The most recent transaction by the Trust is the Rancho Seco and Santa Lucia Ranch, which comprises 10,000 deeded acres that will now be protected forever. This acquisition alone represents 10 percent of all the private lands identified through the project study. The protection of these lands is contributing significantly to the overall goal of the Sonoran Desert Conservation Plan.

For more information, contact Diana Freshwater, executive director, Arizona Open Land Trust, Tucson, Arizona (tel.: 520-577-8564, e-mail: dbfreshwater@aolt.org, Web: www.aolt.org).