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Global Survey of Anthropogenic Neighborhood Threats to Conservation of Grass-Shrub and Forest Vegetation
Citation:
Riitters, K. H., J. D. WICKHAM, T. G. WADE, AND P. Vogt. Global Survey of Anthropogenic Neighborhood Threats to Conservation of Grass-Shrub and Forest Vegetation . ENVIRONMENTAL MANAGEMENT. Springer-Verlag, New York, NY, 97:116-121, (2012).
Impact/Purpose:
As an expanding human population consumes an ever-increasing share of the natural environment for agriculture, housing, and commerce, there is no choice but to adopt integrated landscape approaches to address the resulting resource management conflicts. Maps showing the locations of natural resources have always been fundamental to resource analysis and land management. The modern need is for maps to be even more explicit about the spatial arrangement and patterns of resources, especially in relation to human activities. This is underscored by headline issues such as Lyme disease, wildfire in suburban neighborhoods, and preservation of green space. In ecology, maps showing the spatial patterns of resources are motivated by an emphasis on spatial heterogeneity and the reciprocal effects of resource patterns and ecological processes (e.g., Wu and Hobbs 2002; Fortin and Agrawal 2005). Human influences, spatial heterogeneity, and resource patterns may be easy to see on a resource map, but those visual perceptions must be quantified rigorously and mapped before they can be included in modern resource analyses and landscape management (Riitters and others 2000).
Description:
We report a survey of land cover patterns focusing on forest, grassland, and shrubland for the United States. To provide information for a national resource assessment, an integrated survey of patterns was conducted using a circa 2001 land cover map. The survey was designed to achieve a robust evaluation of land cover pattern itself, while preserving options for interpreting the causes or the effects of patterns and thereby promoting interdisciplinary and integrated applications of the results. Pattern was defined as a contextual (neighborhood) attribute with measurements of land cover structure and composition, and the results were mapped at the same spatial resolution as the input land cover map. This report illustrates potential applications of those maps in national resource assessments, and uses the data to compare the fragmentation of forest, grassland, and shrubland land cover at national scale. Edge effects extending 30 m into intact land cover potentially impact 40% of all grassland area, 28% of all forest area, and 30% of all shrubland area. Grassland was the most fragmented and shrubland was the least fragmented for six neighborhood sizes from 4 ha to 478 sq km, and for three fragmentation thresholds selected to represent intact, interior, and dominant land cover. Overall forest fragmentation was similar to grassland fragmentation in larger neighborhoods and for higher fragmentation thresholds, and similar to shrubland fragmentation in smaller neighborhoods and for lower fragmentation thresholds.