Overview of Conceptual Frameworks

A number of general wilderness frameworks have been established to provide a conceptual basis to understand protected areas. One of the earliest was provided by Brown and others (1978) who developed the Recreational Opportunity Spectrum (ROS), an approach that was based on characterizing resource, social, and managerial conditions for parks and recreation areas. The ROS has less well-developed guidance for characterizing threats and conservation on working and private lands. In Australia, Lesslie and Taylor (1985) developed the wilderness continuum concept that provided the basis for developing an inventory of high-quality wilderness areas. More recently, Cordell and others (2005) provide a concise review of the two most widely accepted attributes of wildlands: naturalness and wildness.

A number of efforts have built on these conceptual frameworks to provide detailed characterizations of wilderness through fine-grained mapping. Lesslie and others (1988) provide an early mapping technique based on overlaying distance classes from settlement and road infrastructure. Kliskey (1998) developed a method to better link perception of wilderness to the ROS in a spatially explicit mapping framework. Aplet and others (2000) developed a nationwide map of wilderness by distinguishing managed from natural landscapes and mapping a multidimensional index at 1-km resolution. Building on earlier work in Australia and the United States, Sanderson and others (2002) mapped the human footprint for the entire globe at 1-km resolution.

More recently, scientists have been moving from employing general indicators of wilderness (or degree of human modification) to recognizing specific indirect and direct threats, (e.g., to wilderness ecosystems by Cole and Landres 1998) and the relative degree to which different types of protected areas function to protect biodiversity. A common approach to categorizing or organizing different types of protections or threats has been to define categories based on whether land is managed for permanent biodiversity maintenance through some legal or institutional mechanism, or both. Both the World Conservation Union (IUCN) and the U.S. Geological Survey’s Gap Analysis Program (GAP) use this approach, though their protection categories differ somewhat (Davey 1998, Scott and others 1993). For example, the IUCN contains 8 categories (IUCN 1994): I–scientific reserve/strict nature reserve; II–national park; III–natural monument/natural landmark; IV–managed nature reserve/wildlife sanctuary; V–protected landscapes; VI–resource reserve; VII–natural biotic area/anthropological reserve; and VIII–multiple-use management area/managed resource area.

The USGS Gap program found these too vague for their uses, and so they devised a stewardship classification with four status classes (Csuti and Crist 2000): (1) permanent protection from conversion of natural land cover, with natural disturbance events allowed; (2) permanent protection and some suppression of natural disturbance; (3) some extractive uses permitted; and (4) no protection from conversion of natural land cover.

The Land-Based Classification Standards (APA 2003) provide a multidimensional land use classification model based on five characteristics: activities (land use based on observable characteristics), functions (economic purpose), building types (structures), site development character (physical characteristics such as land cover types), and ownership constraints (private vs. public, or other legal devices to constrain use). They are richly developed for private land but are less directly applicable to public protected or conserved areas.

The IUCN categories have been revised substantially in the Conservation Measures Partnership, a collaborative effort mostly among nongovernmental organizations that includes The Nature Conservancy, World Wildlife Fund, and Conservation International, in addition to the IUCN. They recognize 11 classes of direct threats (IUCN-CMP 2006): residential and commercial development; agriculture and aquaculture; energy production and mining; transportation and service corridors; biological resource use; human intrusions and disturbance, (e.g., recreation, war, etc.); natural system modifications, (e.g., fire suppression); invasive species and genes; pollution; geologic events; and climate change and severe weather.

A number of additional alternative approaches are emerging quite rapidly. For example, the human footprint represents in a general way the total of ecological footprints of the human population as a continuum of human influence stretched across the land surface (Sanderson and others 2002). Implicit in nearly all of these approaches is that if an area is of high value, and it is unprotected, then it is vulnerable. However, incorporation of threat directly into these frameworks is underdeveloped, and these approaches have been critiqued because they neglect a means to assess the relative imminence or urgency—are some gaps more important than others, and, if so, which ones? (Margules and Pressey 2000, Theobald 2003).