An analysis of landscape penetration by road infrastructure and traffic noise

Abstract

The rapidly expanding road infrastructure and vehicular traffic worldwide has been increasingly recognized as a major contributor to the global biodiversity crisis. An important question for mitigating this effect concerns the quantification of the rate and extent of road-induced penetration of the landscape. However, such an assessment has been largely lacking, especially at the landscape level. The article introduces a GIS-based metric to measure the amount of space un-penetrated by roads and vehicular traffic at the landscape level: Effective Roadless Volume (ERV). ERV is based on measuring the shortest distance between any location and the nearest road and on quantifying the propagation of traffic noise over the landscape. ERV is illustrated by analyzing the rate and extent of human penetration on the landscape in Dakota County, one of the seven counties that make up the greater Twin Cities Metropolitan Region of Minnesota. The results indicate that by as early as 1937 the county had already consumed as much as 65% of its roadless space. Between 1937 and 2007, roadless space declined further by approximately 39% and 26% with and without traffic noise, respectively. The reduction in roadless space showed strong regional differences, with the highest reduction occurring in places where the rate of urban growth and vehicular traffic noise was the highest. The sensitivity of the approach to the size, shape, and spatial configuration of roads as well as to traffic noise suggests that the approach can serve as an important planning tool for reconciling conservation and development in a wide range of contexts.