This project investigated how climate change over the last 21,000 years, which was characterized by significant warming, influenced vegetation in the Southern and Middle Rockies. We found that rapid vegetation change was initiated across these landscapes once a 2 ℃ temperature increase was realized and again recently with reduced rainfall. Southwesterly slopes in the Southern Rockies were prone to rapid change, otherwise landscape features didn’t have a strong effect. We also examined vegetation transformations (e.g., sagebrush steppe switches to a lodgepole pine forest) and identified between one and four vegetation transformations at each site, for a total of 60 transformations, over half of which occurred rapidly....