BLM Roadless Core Areas

The roadless areas (i.e., cores) depicted as polygons in this shapefile were derived for an analysis of potential conservation priority areas on Bureau of Land Management (BLM) lands across 11 western states: Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming. A more detailed description of the methods used to derive this data layer can be found in Dickson et al. (2014). Because we were interested in identifying candidate areas that could also meet the criteria for the highest level of protection, i.e., wilderness designation, we also required lands in the analysis extent to be contiguous areas > 20.2 square-kilometers (or 5,000 ac, by convention the minimum size for wilderness designation in the U.S.) after removal of areas otherwise occupied by roads, railroads, and electric power transmission lines. The BLM defines ‘roadless’ as the absence of roads that have been improved and maintained by mechanical means in order to insure relatively regular and continuous use. Recognizing that no comprehensive dataset exists for all BLM lands that differentiates between maintained and unmaintained roads, we used US Census Bureau 2011 TIGER/Line roads data to buffer (5 m per side) and remove all documented linear road features from the analysis extent. Additionally, we removed railroads and powerlines, also using a 5-m buffer. Areas < 20.2 square-kilometers in size or otherwise highly influenced by the ‘checkerboarding’ effect of private and other state inholdings also were removed from consideration in our analysis extent. Areas included in our analysis were located outside of existing special designations, including national monuments, wilderness areas, and wilderness study areas (WSAs). We excluded WSAs because they are provisionally protected until their designation is changed through legislative action by the U.S. Congress. We used land management designations in the U.S. Protected Areas Database (USGS GAP 2011)to identify and remove the aforementioned lands from our analysis extent.

We defined our analysis extent using readily available data on current road networks. Nevertheless, our results likely reflect errors in these data that would be difficult to quantify over an 11-state region, so we urge data users to scrutinize areas we assumed to be ‘roadless.’ Users should also be mindful of high value areas within BLMs jurisdiction where errors of commission (i.e., the presence of a road is falsely indicated by the TIGER/Line data) could have resulted in these areas being excluded from our analysis.

Full metadata can be viewed upon download in the file named 'metadata1_original.xml'

Dickson, B.G., L.J. Zachmann, and C.M. Albano. 2014. Systematic identification of potential conservation priority areas on roadless Bureau of Land Management lands in the western United States. Biological Conservation, 178:117-127.

USGS GAP (2011) Protected Areas Database of the United States (PADUS), version 1.2. Available: http://gapanalysis.usgs.gov/data/padus-data/.