Rangelands in the United States encompass a diversity of ecosystems, including the prairies of the Midwest and Great Plains, sagebrush shrublands, deserts, mountain meadows, and tundra in Alaska. The Bureau of Land Management (BLM) manages nearly 244.4 million acres of federal lands in the lower 48 states and Alaska, of which 194 million are rangelands. The BLM’s standardized rangeland monitoring program, the Assessment, Inventory, and Monitoring (AIM) program, is designed to determine the status, condition, and trend of BLM’s rangeland ecosystems. These monitoring data provide a unique opportunity to understand the ecological condition of western United States rangelands at both local and ecoregional scales. Here we present preliminary results from the first 8 years of the national AIM monitoring program. We explore how dynamics of biotic integrity - including non-native invasive species, hydrologic function, and soil/site stability at the ecoregional scale are influenced by both wildfire and BLM vegetation treatment and restoration activities.
Results/Conclusions
We analyzed AIM monitoring data on BLM land in 11 Level II and Level III ecoregions in the western United States between 2011 and 2018. During that same period, over 21 million acres (12 %) of BLM lands burned in wildfire, which correlated to an increase in invasive species. Non-native invasive plants were found in all ecoregions and were present on 57% of BLM acres in 2011 compared to 62% of BLM acres in 2018. Non-native invasive plants also increased on BLM rangelands, with percent of rangelands where invasive plants were common (>25% of vegetation cover) increasing from about 17% in 2011 to over 25% in 2018. In response to wildfire and invasive species threats and wildlife habitat loss, BLM completed over 500 vegetation treatments on 8.4 million acres, including post-fire seedings, weed removal, fuels reduction, and encroaching shrub and tree species removal. Despite the wildfire and invasive species increase, ecological condition appears to be static or improving on all ecoregions except the Madrean Archipelago. These results indicate a nuanced story of ecological condition of BLM lands and highlight the importance of continued monitoring as these trends may be further understood over longer time periods. While current conditions are stable, non-native invasive species spread, accelerated by wildfire, could have broad impact on these rangeland ecosystems.