Learning more about the Conservation Land System...

Conservation Land System (CLS)

The CLS is considered the backbone of the Sonoran Desert Conservation Plan (SDCP). All of the land within Pima County has been given a designation based on the biological value of the habitat. The CLS was constructed based on the science of the SDCP with participation and oversight by the SDCP Science Technical Advisory Team (STAT) and according to the most current tenets of conservation biology and biological reserve design. The five tenets are as follows:

• Perpetuates the comprehensive conservation of vulnerable species;
• Retains those areas that contain large populations of focal vulnerable species;
• Provide for the adjacency and proximity of habitat blocks;
• Preserves the contiguity of habitat at the landscape level; and
• Retains the connectivity of reserves with functional corridors.

The collective application of these individual tenets produces a CLS that retains the diverse representation of physical and environmental conditions, preserves an intact functional ecosystem, minimizes the expansion of exotic or invasive species, maximizes the extent of roadless areas, and minimizes fragmentation.

A map of the CLS can be found at www.dot.pima.gov/cmo/SDCPmaps. If you have never used MapGuide® on your computer you must first download a browser plug-in. The instructions and site are found on the same page (see above). It is necessary to zoom in on the map in order for the following CLS categories to appear in the menu on the left hand side of the screen.

The CLS is a set of guidelines for open space set aside for development projects that must go through the rezoning process. If a landowner develops on his/her property and does not request a higher density zoning than the CLS does not take affect.

The categories are as follows:

• Important Riparian Areas (IRA): The guidelines call for 95% Open Space set aside in these areas. These areas are designated for their high water availability, vegetation density, and biological productivity. Not all washes are designated as IRAs. These areas are shown as blue on the CLS map.

• Biological Core: The guidelines call for 80% Open Space set aside in the Biological Core areas. These lands fulfill the five tenets mentioned above and are designated for their potential to support high value habitat for 5 or more priority vulnerable species identified under the SDCP and provide greater biological diversity than Multiple Use Management Areas. These areas are shown as dark green on the CLS map

• Special Species Management Areas: The guidelines call for 80% Open Space set aside in these areas. These areas are defined as crucial for the conservation of specific native floral & faunal species of special concern of Pima County. Management of these areas will focus on conservation, restoration, and enhancement of habitat for these species. Much of this designation overlaps with Multiple Use Management Areas, but will retain the 80% set aside percentage. These areas are shown as hash marks over other CLS designations on the CLS map.

• Multiple Use Management Areas: The guidelines call for 66& 2/3% Open Space set aside in these areas. These lands fulfill the five tenets mentioned above, but are not as biologically rich as those areas designated as Biological Core. These areas are primarily distinguished from other lands within the CLS by their potential to support high value habitat for 3-4 priority vulnerable species identified under the SDCP. Any overlap of the Special Species Management Areas over Multiple Use will use the 80% set aside percentage. These areas are shown as light green on the CLS map.

• Critical Landscape Connections: There is no set aside percentage for Open Space since they lay within other CLS designated lands. These are broadly defined areas that provide connectivity for movement of native biological resources but which also contain potential or existing barriers that tend to isolate major conservation areas. Any land-use change in these broadly defined areas should protect existing biological linkages. Where barriers already occur, those barriers should be removed or modified to allow biological movement through the landscape connections. These areas are numbered on the CLS map and show the general location of these connections.

• Agriculture Holdings within the CLS: There is no set aside percentage for Open space in this designation. This designation identifies lands currently utilized for agriculture purposes and lands where agriculture uses have been abandoned. Intensifying land uses of these areas will emphasize the use of native flora, facilitate the movement of native fauna and pollination of native flora across and through the landscape, and conserve on-sight conservation values on-site conservation values when present. Development within these areas will be configured in a way that does not compromise the conservation values of adjacent and nearby CLS lands. These areas are shown as off-white or light yellow on the CLS map.

Four of the above CLS categories call for Open Space set aside. The percentages stated are for on-site mitigation. If for some reason the landowner exceeds the developable percentage stated the guidelines state that land must be purchased off-site to off-set the disturbance of lands that would otherwise be preserved. This off-site mitigation calls for more acres to be purchased when the percentage of disturbance is greater than that allowable under the guidelines. A purchase to disturbance ratio is given. This ratio states how many acres are to be purchased off site dependant on how many acres above the allowable percentage of developable area is disturbed. Important Riparian Areas do not have a stated off-site mitigation ratio. The goal is to protect all natural resources in these areas on-site because of the high biological value and scarcity.

Off-site mitigation ratios are as follows:

• Biological Core: 4:1 ratio when disturbance is greater that 20% of the property.

• Special Species Management Areas: 4:1, when disturbance is greater than 20% of the property.

• Multiple Use Management Areas: 2:1, when disturbance is greater than 35% of the property.

These guidelines are instrumental to building a preserve in Pima County to ensure that the regional health of the desert is maintained and enhanced. The CLS guidelines can be found in Pima County's Regional Plan Policy in the Environmental Element section, where much of the above information was gathered.