Threat‐Based State and Transition Models Predict Sage‐Grouse Occurrence while Promoting Landscape Conservation

Abstract

ABSTRACTA recent collaboration between federal, state and private partners in southeast Oregon developed mental models to distill complex plant‐based community ecology for management. The mental models were then turned into a simplified, habitat‐classification system that addressed landscape‐level threats to the sagebrush ecosystem. The simplified, habitat‐classification system formed the foundation of Threat‐based State and Transition Models (TBSTM). We quantitatively linked greater sage‐grouse (Centrocercus urophasianus, hereafter sage‐grouse) lek occurrence to a landscape‐level habitat classification based upon the TBSTM framework. We investigated whether TBSTM classifications were able to spatially predict locations of sage‐grouse breeding areas equivalently to landcover variables that have been studied for over a decade. We showed the TBSTM framework was able to predict the locations of sage‐grouse accurately (R2 = 0.70, AUC = 0.91, Correctly Classified = 83%). Model fit statistics were similar to the model built with traditional land cover variables (R2 = 0.65, AUC = 0.89, Correctly Classified = 80%). The high degree of model fit for the TBSTM framework allows conservation practitioners a direct, quantifiable, and biological link to understand outcomes of transitioning habitats from various threat states to sagebrush‐dominated landscapes with a perennial understory across large landscapes. Sage‐grouse are well known to respond to landscape‐level amounts of habitat and exhibit low tolerance to threats. We documented similar responses between threats such as the percentage of conifers within 560‐m and the conifer threat bin at the same spatial scale. Our work also quantified the importance of having a healthy perennial‐grass understory and perennial‐grass patches in conjunction with sagebrush cover across large landscapes. Our work suggests that understory grass communities at landscape scales may be limiting grouse occurrence in certain parts of Oregon. © 2021 The Authors. Wildlife Society Bulletin published by Wiley Periodicals LLC on behalf of The Wildlife Society.