Projections of Rangeland Fractional Component Cover Across Western Northern American Rangelands for Representative Concentration Pathways (RCP) 4.5 and 8.5 Scenarios for the 2020s, 2050s, and 2080s Time-Periods

Climate change over the past century has altered vegetation community composition and species distributions across rangelands in the western United States. The scale and magnitude of climatic influences are largely unknown. We used fractional component cover data for rangeland functional groups and weather data from the 1985 to 2023 reference period in conjunction with soils and topography data to develop empirical models describing the spatio-temporal variation in component cover. To investigate the ramifications of future change across the western US, we extended models based on historical relationships over the reference period to model landscape effects based on future weather conditions from two emissions scenarios (Representative Concentration Pathways [RCP] 4.5 and 8.5) and three time periods (2020s, 2050s, and 2080s). We build upon the projections of Rigge 2022 and Rigge et al. 2023, expanding our study area to include the entire Rangeland Condition Monitoring Assessment and Projection (RCMAP) study area (including all the sagebrush biome and Canadian expansion), using updated climate projections (Mahony et al. 2022), and applying a Deep Neural Net (DNN) classifier. In general, both scenarios yielded similar results, but RCP 8.5 tended to be more extreme, with greater change relative to the reference period. This information can be used to inform management to prepare for future vegetation composition and cover through the prioritization of conservation and restoration and shed light on species range shifts.

Mahony, C.R., T. Wang, A. Hamann, and A.J. Cannon. 2022. A global climate model ensemble for downscaled monthly climate normals over North America. International Journal of Climatology. 1-21. https://doi.org/10.1002/joc.7566.

Rigge, M.B., 2022, Projections of Rangeland Fractional Component Cover Across the Sagebrush Biome for Representative Concentration Pathways (RCP) 4.5 and 8.5 Scenarios for the 2020s, 2050s, and 2080s Time-Periods (ver. 1.1, April 2022): U.S. Geological Survey data release, https://doi.org/10.5066/P9EC2094.

Rigge, M., Postma, K., Bunde, B., and Shi, H., 2023, Projections of Rangeland Fractional Component Cover Across Western US Rangelands for Representative Concentration Pathways (RCP) 4.5 and 8.5 Scenarios for the 2020s, 2050s, and 2080s Time-Periods: U.S. Geological Survey data release, https://doi.org/10.5066/P9J490BH.