Natural Heritage New Mexico used standard photo-interpretive techniques to survey 1,654 digital orthophoto quarter quads (DOQQs) for ground disturbance caused by GPD. The surveyed area covered 7,944,262 ha. To assess accuracy, field observers walked 101, 2 km transects on the Navajo Nation and 50 on the Hopi Reservation, distances of approximately 202 and 100 km, respectively. On the surveyed DOQQs we delineated 40,587 ha of apparent GPD disturbance. We found apparent GPD disturbance that, when confirmed on the ground, will extend the GPD range up to 50 km to the northwest.