Vegetation cover

The Rangeland Analysis Platform's vegetation cover data provides annual percent cover estimates from 1984 to 2017 of: annual forbs and grasses, perennial forbs and grasses, shrubs, trees, and bare ground. The estimates were produced by combining over 30,000 field plots from the NRCS National Resources Inventory (NRI) and the BLM Assessment, Inventory, and Monitoring (AIM) datasets with the historical Landsat satellite record, gridded meteorology, and abiotic land surface data (e.g., elevation, soils).

Utilizing the computation power of Google Earth Engine, annual estimates and maps are produced across the western half of the U.S. at 30 m resolution. This means that each pixel is slightly larger than a baseball diamond.

When interpreting the modeled vegetation cover, it is important to consider the model error specific to each vegetation cover class, as shown in the following table:

Vegetation cover Annual forbs
and grasses
Perennial forbs
and grasses
Shrubs Trees Bare ground
Mean absolute error (%) 7.8 11.1 6.9 4.7 7.3
Root mean square error (%) 11.8 14.9 9.9 8.5 10.6

These errors provide an accuracy assessment. In basic terms, the vegetation cover value of a given pixel should be thought of as plus or minus the error. For example, the confidence of a 35% annual forb and grass pixel is +/- 7.8% (mean absolute error). Error metrics are notably higher for perennial vegetation due to the greater possible range of values, particularly in the Great Plains regions.

The vegetation cover data and maps are intended to be used alongside local knowledge and on-the-ground data to inform management actions that improve rangelands and wildlife habitat. They should not be used in isolation to quantify rangeland resources, determine or define cover thresholds, or evaluate the efficacy of management practices or treatments. The RAP tool can be used to evaluate resources in concert with site-specific information about the area under investigation, such as past land management practices, vegetation treatments, conservation efforts, or natural disturbances.

Jones, M.O., B.W. Allred, D.E. Naugle, J.D. Maestas, J.D. Donnelly, L.J. Metz, J. Karl, R. Smith, B. Bestelmeyer, C. Boyd, J.D. Kerby, J.D. McIver. 2018. Innovation in rangeland monitoring: annual, 30m, plant functional type percent cover maps for US rangelands, 1984–2017. Ecosphere 9:e02430 10.1002/ecs2.2430