GLO surveys show change over the past century in a semiarid landscape in the area of Dinosaur National Monument, Colorado/Utah

The vegetation of Dinosaur National Monument and surrounding lands (~298,000 ha) was reconstructed using the General Land Office (GLO) survey records. This historical dataset was compared to modern vegetation datasets to determine how vegetation has changed over 90 years. Significant net declines in pinon-juniper woodland and montane shrubland occurred, along with large increases in sagebrush shrubland. Shorter natural and human-caused fire rotations appear to be driving woodland contraction. Some natural pinon-juniper expansion did occur near historical pinon-juniper-sagebrush ecotones, and particularly at elevations of 2000-2400 m and slopes of 10-30%. If trends continue, an artificial landscape with significantly more early seral sagebrush and grassland and less pinon-juniper woodland will emerge. Declines of pinon-juniper shown in Dinosaur National Monument and surrounding lands are similar to the recent loss of woodland in Mesa Verde National Park, Colorado, and suggest that historical woodlands on the Colorado Plateau may be declining due to an excess of fire since Euro-American settlement.