Conservation Subdivision

Conservation subdivision (CS) is one of a number of site-scale design approaches that address the well-documented environmental impacts of traditional subdivision in suburbia and exurbia. As an urban design approach, CS is often associated with the urban development philosophy known as New Urbanism (NU), but it has clear ties to the emerging [Page 117]philosophy of New Ruralism (NR). Perhaps the best-known example of CS in the United States is Prairie Crossing in Grayslake, Illinois, which features both NU and NR components. CS can be found in other parts of the United States, and it may be relatively common in some regions. At the same time, the approach has encountered economic and social-political barriers. In the few published empirical studies on the use of specific CS design features, several concerns about the practice have emerged. These suggest ways in which its use can be improved in the future.

CS, also known as open space subdivision, generally features five characteristics. First, the layout of lots (development pattern) is altered to avoid areas that have sensitive environmental resources (e.g., biodiversity, natural habitats, wetlands, riparian areas), support productive land for the management of natural resources (e.g., agriculture, timber, grazing lands), or offer diverse recreational opportunities (e.g., active and passive forms). Second, the design reduces the lot sizes, often to much smaller sizes than allowed by typical zoning, to maximize open space and thereby reduce infrastructure needs. Third, the project design often clusters these smaller lots together to further maximize open space size and contiguity. This may further reduce infrastructure needs, thereby improving water quality and hydrological dynamics in nearby waterways. Fourth, legal prohibitions against future development are placed on designated open space. This may occur through deed restrictions, conservation easements held by a local government or land trust, dedication or sale of the land to a government entity, or land donation to a land trust. Fifth, the developer creates a homeowners association and specific bylaws that encourage ecologically appropriate resident interactions, both in protected areas and on their own properties.

Although NU principles emphasize compact design, mixed-use development, and walk-able neighborhoods that promote high quality of life, NR protects productive farmlands, supports small-to-medium agricultural enterprises, and maintains overlapping wildlife habitats that facilitate sustainable agriculture. Key features of CS predate recent trends toward designing ecologically friendly human settlements. Randall Arendt popularized CS practices in his 1996 book Conservation Design Subdivisions: A Practical Guide to Creating Open Space. However, elements of CS, such as ideas about locating development according to biophysical features, can be traced back to the teachings of Ian McHarg, whose 1969 book Design With Nature inspired many landscape architects and planners to think differently about nature in the built environment. More recently, emphasis is being placed on using this approach for landscape- and regional-scale efforts to create greenways, including the ecological corridors advocated by conservation biologists.