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Assessing and Managing the Ecological Impacts of Paved Roads
cused on spatial scales from meters to hundreds of kilometers. Temporal scales included in this report range from days to a few decades.
In confronting the broad range of scales covered by ecosystems and road systems, the approach has been to divide the scales into research, assessment, and management categories. As shown in Chapter 3, most research on, and understanding of, ecological effects covers small scales—road segments and corridors. The committee has inferred effects at larger scales (disruption of landscapes and spread of exotic organisms), but few studies cover these scales. In all of these studies, bounds are established that define a discrete scale range. Studies are bounded in space (for example, meter square plots to hundreds of hectares) and time (for example, days to years), whether they are field investigations or modeling-based inquiries. As with the understanding of ecosystems, the scales for road planning, assessment, and operation are also divided; long-range transportation plans (LRTPs) cover regions and decades, and state transportation improvement plans cover road segments and years (see Chapters 3 and 6). This division of scales has its roots in theory, as described in Chapter 3; Chapter 3 also discusses cross-scale effects and their relevance to road ecology. The remainder of this chapter focuses on integrating social (including legal, institutional, and economic) and ecological issues.
Scales of Law, Planning, Assessment, and Financing
Federal laws apply to the lands within the United States, unless specified otherwise, and thus cover a wide range of spatial scales, from a very small scale (molecular level for water or air quality) to a national scale. State laws are restricted to the geographical extent of that specific state and may address environmental concerns in relation to roads. Even though these laws cover a conceptually wide area (the nation), the spatial scope is narrowed greatly during the planning and assessment process. For example, consideration of wetland resources is only applied to specific areas where wetland ecosystems occur. Similar restrictions are applied to endangered species consideration, generally applied to a specific population and habitat, regardless of wider distributions. Hence, there appears to be a consideration of the relationship of immediate (spatial scale) impacts on wetlands and on endangered species, but insufficient consideration of how those immediate impacts relate to impacts on a greater scale. This narrowing in scope of federal statutes requiring envi-