The Conservation Lands System (CLS) is considered the backbone of the Sonoran Desert Conservation Plan (SDCP). 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 of the CLS are to:
- Perpetuate the comprehensive conservation of vulnerable species;
- Retain those areas that contain large populations of focal vulnerable species;
- Provide for the adjacency and proximity of habitat blocks;
- Preserve the contiguity of habitat at the landscape level; and
- Retain the connectivity of reserves with functional corridors.
The collective application of these individual tenets produced 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.
Along with a map identifying various categories of environmentally-sensitive lands, the CLS includes an associated set of open space preservation guidelines for development projects that must go through the rezoning process or some other discretionary action. If a landowner develops on his/her property and does not request a higher density zoning, then the CLS does not take effect.
CLS land categories include:
- Important Riparian Areas (IRA): 95% open space set aside, designated for their high water availability, vegetation density, and biological productivity. Not all washes are designated as IRAs.
- Biological Core: 80% open space set aside, 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.
- Special Species Management Areas: 80% open space set aside and 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.
- Multiple Use Management Areas: 66& 2/3% open space set aside with a 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.
- Critical Landscape Connections: no set aside percentage for open space since they lay within other CLS lands. 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.
- Agriculture Holdings within the CLS: 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 conservation values on-site 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.
If for some reason the landowner exceeds the developable percentage allowed, CLS guidelines state that land must be purchased off-site to off-set the disturbance of lands that would otherwise be preserved. The off-site mitigation guidelines call for a specific purchase to disturbance ratio depending on the CLS category. 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 robust open space preserve system in Pima County to ensure that the regional health of the desert is maintained and enhanced. The full text of the CLS guidelines can be found in Pima County’s Regional Plan Policy in the Environmental Element section.
The Coalition successfully works with private property owners to apply Conservation Lands System guidelines to their projects. This largely consists of the inclusion of contiguous natural open space on their properties, and occasionally mitigation through the set-aside of other parcels of land.