Public lands and private waters: scarce mesic resources structure land tenure and sage-grouse distributions

Water scarcity in semiarid environments provides a model system to evaluate the role of mesic resources in structuring the distribution and abundance of wildlife. We used remote sensing and point process analyses to evaluate spatio-temporal variability in limited mesic resources in relation to greater sage-grouse (Centrocercus urophasianus) distributions in Oregon, California, and northwest Nevada, USA, 1984-2011. We then link population distribution to changes in resource availability over time, space, and land tenure. Despite encompassing only 2.4% of landscape area, mesic sites influenced sage-grouse breeding distributions as evidenced by significantly shorter lek to mesic resource distances in observed (5.3 km) vs. predicted (8.2 km) values. Population abundance increased with proximity to mesic sites. Lag effects evident in abundance and proximity trends of mesic resources suggest a level of drought tolerance that moderated climatic variability. Mesic abundance and proximity remained relatively stable during the study period in comparison to more dynamic climatic patterns. Drought effects were most pronounced during multiyear events as evidenced by the 1987-1992 period that decreased mesic abundance >25% and approximately doubled mean lek to mesic resource distances (4.8-8.3 km). In our study area, 75% of all mesic resources were in private ownership, where the predominant land use is livestock ranching. Results suggest a holistic conservation strategy inclusive of private and public lands is needed to ensure sage-grouse habitat requisites are met throughout the life cycle of this landscape species.