How do you map the historical distribution of Wyoming’s only endangered plant species when nobody even acknowledged the species in Wyoming until 1996? BLM and University of Wyoming researchers attempted to address this problem by mapping the unique habitat of blowout penstemon (Penstemon haydenii) using historical aerial imagery. Blowout penstemon in Wyoming is restricted to 19 active sand dunes in the Ferris dunefield of central Wyoming, and is associated with the loose sand downwind of blowout rims, slopes and slip faces that is visible in aerial photos. Images from 13 dates collected as far back as 1946 and spanning over 66 years were scanned and orthorectified to delineate potential habitat.
Results showed that all dunes currently containing populations of penstemon were present in 1946. Overall, dunes migrated downwind, with the fastest dune migrating 18 meters/year. The faster migrating dunes had smaller populations, and dune size was not correlated with dune migration rate. In 2012, “active dune” and “downwind dune” areas were both about 14 percent smaller than the 66-year mean, indicating a loss of habitat, though not as severe as that seen for the Nebraska penstemon population. The potential habitat for the Wyoming population has been more stable over time than the habitat for the Nebraska population, indicating a potentially lower threat to the species existence. The mobility of habitat emphasizes the need for landscape-scale management of penstemon.
Potential habitat in the form of Total Active Dune (left) and Downwind Active Dune (right) of Dune 8 in 1946 versus 2012. Note: Wind direction is from southwest to northeast.