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The invasive woody species, Russian olive (Elaeagnus angustifolia L.), was promoted in the early 20th century to serve as field wind-breaks and bank stabilization, but quickly became naturalized within riparian systems throughout the semi-arid northwest. The Bighorn and Little Bighorn Rivers of Montana are heavily regulated, and are now heavily dominated by the invasive Russian olive, which are quickly replacing native plains cottonwood (Populus deltoides L.). Historically to present day, the Crow Tribe in south-central Montana use cottonwoods for ceremonial purposes, yet Tribal Elders have expressed concern over their decline. We used the Maximum Entropy Modeling tool (MaxEnt) to predict suitable habitat and near-term future spread of Russian olive within riparian systems on the Crow Indian Reservation. Climate variables (n = 22) contributed significantly to the model, suggesting that climate change may contribute to the spread of Russian olive, particularly downstream from dams. Interviews with Tribal Elders overwhelmingly agreed (~80%) that sub-adult trees were the most difficult to find now, as compared to 25 years ago. Perceptions of cottonwood availability by Elders matched the field plot data using cottonwood stem heights comparing near (< 150m) ceremony sites to sites farther away (> 2.4 km away; p < 0.01). Coupled with local perceptions of reduced cottonwood availability, we suggest that mid-sized cottonwoods may become increasingly difficult to locate for ceremonial purposes. Containment of Russian olive and management plans to increase cottonwood availability will protect the cultural as well as the ecological integrity of these important riparian systems.