Pima County, AZ set out on a mission to revise its land use practices in 1998 after discovering the endangered pygmy owl.  It has resolved to meet a lofty, yet valiant, goal: to “ensure the long-term survival of the full spectrum of plants and animals that are indigenous to Pima County through maintaining or improving the habitat conditions and ecosystem functions necessary for their survival” (Sonoran Desert Conservation Plan).

To do this, the technical team working on the Sonoran Desert Conservation Plan (SDCP) focused on an ecosystem-based growth management strategy and created the Conservation Lands System (CLS), which consists of a map and a set of land categories and associated conservation practices.  There are four main land conservation categories in the CLS (all conservation guidelines are meant to be per parcel to be fair to all property owners):

1. Important riparian areas are valued for their higher water availability, vegetation density, and biological productivity.  Riparian areas also serve as a framework for linking landscapes and associated habitats. At least 95% of the total acreage should be conserved in a natural or undisturbed condition.
2. Biological core management areas are valued for their potential to support high value habitat for five or more priority vulnerable species as identified by the SDCP. At least 80% of the land shall be conserved in undisturbed natural condition.
3. Multiple use management areas are valued for their potential to support high value habitat for three or more priority vulnerable species as identified by the SDCP.  At least 66% of the land shall be conserved in undisturbed natural condition.
4. Critical landscape connections are valued for providing connectivity for movement of native biological resources but also contain potential or existing barriers that isolate major conservation areas.  Barriers to the movement of flora and fauna are to be removed in these priority corridors.

It’s estimated that the implementation of the plan’s biological conservation and restoration guidelines will protect nearly 600,000 acres of important habitat in a biologically sound spatial pattern (Layzer, 2008).  And so far, Pima County has diligently applied the CLS’s stringent standards to nearly every rezoning request approved since 2002 (Layzer, 2008).  But, the CLS are still only guidelines and not yet codified within the county’s local ordinance.  Pima County’s zoning code does require the inclusion of the CLS as an element in all comprehensive plans, but does not detail the rigidity of implementation (Pima County, Arizona, Municipal Code § 18.89.031). The long-term success of the SDCP is still at risk due to the voluntary nature of its implementation.  A change in county leadership could easily disregard the guidelines if the political context changes.

The Sonoran Desert Conservation Plan is certainly a model plan for ecosystem-based growth management, but the county may need to codify the guidelines to make sure their vision becomes reality.

Print Sources

Layzer, J. A. (2008). Natural experiments: Ecosystem-based management and the environment. Cambridge, Mass: MIT Press.