Invasive cheatgrass - Robb Hannawacker, NPS
Cheatgrass began invading the Great Basin about 100 years ago, changing large parts of the landscape from a rich, diverse ecosystem to one where a single invasive species dominates. Cheatgrass is highly flammable; consequently, cheatgrass-dominated areas experience more fires that burn more land than in native ecosystems, resulting in economic and resource losses. Therefore, the reduced production, or absence, of cheatgrass in previously invaded areas during years of adequate precipitation could be seen as a windfall. However, this cheatgrass dieoff phenomenon creates other problems for land managers such as accelerated soil erosion, loss of early spring food supply for livestock and wildlife, and unknown recovery pathways.
We used satellite data and scientific techniques to map annual estimated cheatgrass percent cover and areas of cheatgrass dieoff in the western and central parts of the northern Great Basin from 2000 to 2010. For this same area, we developed a map of cheatgrass percent cover variability and another map that displays cheatgrass dieoff probability.
These maps can assist land managers in understanding when and where cheatgrass did and did not exist over an extremely large landscape, and can possibly explain characteristics of dieoff areas that can help researchers pinpoint the cause or causes of cheatgrass dieoff. The cheatgrass dieoff maps show that dieoff areas are spatially and temporally variable; in other words, a dieoff may impact an area for a few years and then cheatgrass may return, only to dieoff again later. This pattern of variability also persists in different areas. During the study period, we estimated that, on average, about 2.6 million acres experienced cheatgrass dieoff annually.
Restoring dieoff areas to a native ecosystem could be land management’s goal, but until cheatgrass dieoff causes and natural recovery pathways are better understood, engaging in costly restoration activities may be unwise.
