Broad-scale assessment of biophysical features in Colorado

Information on ecological communities, soil salinity, and land use was synthesized and summarized for all lands in Colorado. This biophysical information was requested by the Bureau of Land Management (BLM) for use in conducting an environmental assessment prior to the transfer of ownership (conveyance) of federal lands to the State of Colorado. The Enabling Act of 1864 provided for the conveyance of federal lands to the State for the support of schools. If designated lands were unavailable for transfer at the time of statehood in 1875, the Act provided for the transfer of alternative federal lands in compensation, using a process referred to as "school-land indemnity selection." To initiate indemnity selection, the Colorado State Board of Land Commissioners filed a selective application "to obtain public land and mineral estate in lieu of lands to which the State did not receive" at the time of statehood. To address this legal obligation, 339 parcels of federal lands (organized into 89 Indemnity Units) currently under management by the BLM have been identified as suitable for transfer to the State. The Indemnity Units encompass 23,130 acres of both surface and mineral estate, as well as 6,150 acres of only mineral estate. The specific land parcels to be conveyed to the State will be finalized after an environmental analysis and other evaluations are completed.

The 89 Indemnity Units are widely distributed across Colorado consequently, we compiled four statewide datasets on the biophysical features of interest. To map ecological communities, we derived vegetation types primarily from LANDFIRE Existing Vegetation Types. We used ancillary datasets to improve vegetation type assignments, as described in the supplemental document (SupplementaryMethods.pdf) included in this data release. The final vegetation types were classified into 27 ecological communities and six land cover classes (a seventh land cover class "Altered vegetation" includes eight altered vegetation types). Soil salinity was mapped using electrical conductance from the Natural Resources Conservation Service, surface soils database (gSSURGO). The spatial patterns of land use was evaluated using the surface disturbance footprint from development (agricultural, energy and minerals, transportation, and urban), which was derived from datasets synthesizing development in Colorado (Reese and others, 2017). We used the terrestrial development index to quantify the development footprint at two analysis scales (1-km and 5-km radius window sizes).

The "Broad-scale assessment of biophysical features in Colorado" data release is organized into four raster datasets: "Ecological communities," "Soil salinity using electrical conductance," "Terrestrial development index using 1-kilometer moving window," and "Terrestrial development index using 5-kilometer moving window." These datasets were used to summarize biophysical information for the 89 Indemnity Units, which is available as a companion data release (Burris and others, 2018). Additional background and summary information is provided in the report associated with both data releases (Carr and others, in review). The statewide datasets included in this data release can be applied to other broad-scale assessments and planning activities in Colorado.

Burris, L.E., Carr, N.B., and Manier, D.J., 2018, Biophysical assessment for indemnity selection of federal lands in Colorado: U.S. Geological Survey data release, https://doi.org/10.5066/F7C24VQ0.

Carr, N.B., Burris, L.E., and Manier, D.J., in review, Biophysical assessment for indemnity selection of federal lands in Colorado: U.S. Geological Survey, Open-File Report, 2018

Reese, G.C., Burris, Lucy, Carr, N.B., Leinwand, I.I.F., and Melcher, C.P., 2017, Southern Great Plains Rapid Ecoregional Assessment-Volume I. Ecological communities: U.S. Geological Survey Open-File Report 2017-1100, 126 p., https://doi.org/10.3133/ofr20171100.