A framework for understanding conservation development and its ecological implications.

Suburban, exurban, and rural development is a leading cause of biodiversity loss and natural resource degradation in the United States. In response to this threat, conservation development has been advanced as a way to combine land development with functional protection for conservation resources. This article provides a review, analysis, and ecological critique of the four principal types of conservation development: (1) conservation buyer projects, (2) conservation and limited development projects, (3) conservation subdivisions, and (4) conservation-oriented planned development projects. Each approach can contribute to landscape-scale conservation, with benefits that include reducing the off-site impacts of development, buffering and connecting protected areas, and conserving imperiled species and ecosystems. However, the benefits of these approaches depend significantly on project density, design, and context. Accordingly, this article offers a framework for differentiating and analyzing these approaches to conservation development for the purposes of research, land-use planning, public policy, and conservation practice.

Keywords: conservation development, land conservation, biodiversity, land use, regional planning

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Over the next quarter-century in the United States, 18 million hectares (ha) of land--an area larger than New England--will be converted to urban, suburban, and exurban development, if recent trends in land use change continue (USDA/NRCS 2007). Indeed, residential development is becoming a ubiquitous force on the American landscape, not only in metropolitan areas but also in amenity- and resource-rich hinterlands such as the Rocky Mountains, the southern Appalachians, and rural New England (Brown et al. 2005, Radeloff et al. 2005a, 2005b). This trend is likely to continue because of population and household growth, increasing land consumption per capita, growing numbers of retirees, and the centrifugal forces of high-speed travel and telecommunications (Heimlich and Anderson 2001).

The ecological impacts of land development are complex and often nonlinear (Hansen et al. 2005). Moderate levels of development--especially when it is carefully planned and designed--can sometimes increase species richness by increasing the diversity of habitat types available on the landscape (Marzluff 2005). On the other hand, conventional land development typically displaces sensitive native species, introduces and promotes the spread of nonnative species, degrades water resources, fragments habitat networks, and diminishes the land's cultural and aesthetic value (Radeloff et al. 2005b). Nationwide, land development is perhaps the foremost threat to endangered biodiversity, as well as a major threat to productive agricultural lands and other natural resources (Czech et al. 2000, AFT 2006). ff left unchecked, suburban and rural sprawl will not only continue to degrade the matrix of private, unprotected land nationwide but, through its off-site impacts, also diminish the long-term viability of protected areas (Hansen et al. 2002, Ewing et al. 2005).

In the United States, conservationists typically seek to protect landscapes and their conservation values mainly by purchasing or obtaining land and conservation easements. Although this approach has been relatively successful in many regions--in part because of the recent growth of the land trust movement (LTA 2006)--it is proving inadequate in areas with substantial development pressure and escalating land values, where conservationists are losing ground to the larger, better-funded real estate development industry. From 1998 to 2002, for example, 500 state and local ballot measures in the United States earmarked a total of more than $20 billion for land conservation, but during the same period the nation's 10 largest real estate developers alone consumed $120 billion of land (TPL 2003, Budesilich and Binger 2004). Likewise, land-use regulation has generally proved too weak and too fragmentary to achieve meaningful conservation in rapidly developing landscapes (Beatley 2000). Given that much imperiled biodiversity exists in rapidly developing regions, conservationists cannot afford to ignore sprawl and the real estate market trends that drive it (Miller and Hobbs 2002). Instead, they must find new strategies that explicitly address these market realities.

One way to mitigate the negative ecological impacts of land development--and perhaps even to harness it as a positive force for conservation--is through conservation development. I define "conservation development" as comprising projects that combine land development, land conservation, and revenue generation while providing functional protection for conservation resources. Within the land-use planning, design, and conservation communities, there is much interest in conservation development, and numerous writings provide definitions, case studies, and guidelines. However, conservation development has received little attention in the peer-reviewed literature, and the work that has been done has focused almost entirely on clustered housing in residential subdivisions as an alternative to conventional sprawling development. Here I provide a broader perspective, arguing that conservation development is not limited to clustered housing but encompasses four categories of land-use strategies, including two that are used primarily as conservation finance mechanisms. Accordingly, this article defines, characterizes, and provides examples of these four approaches to conservation development and proposes this typology as a framework for guiding for future research and practice.

Rather than rely principally on the sparse academic literature related to conservation development, I assess practitioners' actual experience to date with conservation development in the United States and what this experience indicates about the benefits of such projects for landscape-scale conservation. To do so, I draw on four key sources of information: (1) interviews with conservation development practitioners and experts from 2004 to 2006; (2) data on a nationwide sample of conservation development projects; (3) an empirical evaluation of a subset of this sample of projects; and (4) a synthesis and analysis of the peer-reviewed and practitioner literatures in this emerging field.

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Overview of conservation development

To understand the growing phenomenon of conservation development, it is helpful to consider the entire spectrum of land-use projects, which can be classified along two axes based on their development density and their level of conservation (figure 1). Within this spectrum, conservation development includes several different land-use techniques that incorporate varying amounts of development but always achieve a meaningful level of functional conservation. Thus, the distinction between conservation development and conventional development depends on the project's conservation outcome, not on whether a particular land-use technique was employed.

Although there are several types of conservation development--which this article will enumerate--the projects tend to have certain features in common. First, all such projects set aside conservation land, which is either held in fee ownership by a conservation organization or protected by a conservation easement. Second, all of these projects include development (or at least the possibility of development), and it is this development that finances or otherwise makes possible each project's conservation component. Third, conservation development is created through a process of ecologically based planning and design (McHarg 1969, Steiner 2000, Perlman and Milder 2005), whereby planners inventory a site's natural resources and environmental context, and use this knowledge to conserve portions of the site with high resource value while situating development to minimize environmental impacts (Pejchar et al. 2007). Since the boundaries of land parcels rarely coincide with the distribution of valuable natural resources, on most sites it is possible to identify an area of lower conservation value that can be made available for development without encroaching on the more valuable areas (figures 2, 3).

Conservation development also incorporates a variety of design features to reduce the negative impacts of development. For example, many projects situate development in one or more compact nodes to minimize its footprint. Low-impact stormwater management systems that promote natural flow patterns and infiltration are widely regarded as an important part of conservation development, as is a landscaping design that minimizes disturbance to existing vegetation, uses wildlife-friendly native species, and avoids invasive species (TNC/CW 2004). A minority of conservation developments go further to restrict disturbance vectors such as household pets and light pollution. Others address sustainability concerns by incorporating "green building" features such as energy efficiency, renewable energy, and low-impact building materials (Wilson et al. 1998).

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Motivations and driving forces

Conservation development occurs as a result of three principal factors. First, in a growing number of jurisdictions …