Citation:

Riitters, K. H. AND J D. Wickham. HOW FAR TO THE NEAREST ROAD? FRONTIERS IN ECOLOGY AND THE ENVIRONMENT 1(13):125-129, (2003).

Impact/Purpose:

The primary objectives of this research are to:

Develop methodologies so that landscape indicator values generated from different sensors on different dates (but in the same areas) are comparable; differences in metric values result from landscape changes and not differences in the sensors;

Quantify relationships between landscape metrics generated from wall-to-wall spatial data and (1) specific parameters related to water resource conditions in different environmental settings across the US, including but not limited to nutrients, sediment, and benthic communities, and (2) multi-species habitat suitability;

Develop and validate multivariate models based on quantification studies;

Develop GIS/model assessment protocols and tools to characterize risk of nutrient and sediment TMDL exceedence;

Complete an initial draft (potentially web based) of a national landscape condition assessment.

This research directly supports long-term goals established in ORDs multiyear plans related to GPRA Goal 2 (Water) and GPRA Goal 4 (Healthy Communities and Ecosystems), although funding for this task comes from Goal 4. Relative to the GRPA Goal 2 multiyear plan, this research is intended to "provide tools to assess and diagnose impairment in aquatic systems and the sources of associated stressors." Relative to the Goal 4 Multiyear Plan this research is intended to (1) provide states and tribes with an ability to assess the condition of waterbodies in a scientifically defensible and representative way, while allowing for aggregation and assessment of trends at multiple scales, (2) assist Federal, State and Local managers in diagnosing the probable cause and forecasting future conditions in a scientifically defensible manner to protect and restore ecosystems, and (3) provide Federal, State and Local managers with a scientifically defensible way to assess current and future ecological conditions, and probable causes of impairments, and a way to evaluate alternative future management scenarios.

Description:

Ecological impacts from roads may be the rule rather than the exception in most watersheds of the conterminous United States. We measured total area, and forestland area located within nine distances of the nearest road of any type in each of 2,108 watersheds nationwide. Overall, 20% of the total area was within 90 meters of the nearest road, and the proportion increased rapidly with distance such that 83% was within 750 meters of a road and only 3% was more than 3,660 meters away. Forestland area measurements differed by <2% for all distances. There was also substantial geographic variation. For example, the proportion of total watershed area within 270 meters of a road varied from 1% to 94% among watersheds. Geographic "clusters" of watersheds with a substantial portion of area in close proximity to roads were located in Northeast, lower Great Lakes, and Pacific Northwest and Southwest coastal regions, on the southeast Piedmont and coastal plain, and in parts of the Ohio, Brazos, Colorado, San Joaquin, and Sacramento River basins

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