Washington Native Plant Society: Threats to the Shrub-Steppe

Threats to the Shrub-Steppe

The primary ecological threats to sagebrush are: habitat conversion; soil disturbance due to heavy overgrazing, motorized recreation or other intensive land-use activities; invasive species; and altered fire regimes. Over 60% of original shrub-steppe habitats have been converted.

Unconverted areas are threatened by a negative feedback loop that combines disturbance, invasion of noxious weeds and more frequent fires. When fragile soils are disturbed and cryptobiotic soil crusts are removed, annual invasive species such as cheatgrass become established. Activities such as heavy overgrazing also can result in removal of palatable native bunchgrasses. Increased abundance of cheatgrass creates a continuous layer of flammable fuel in a system where vegetation is naturally patchy and sparse, separated by areas of cryptobiotic crust. Fire ignitions occur more frequently due to human activities and are then carried more easily due to cheatgrass invasion. Frequent fires remove sagebrush and increase the abundance of cheatgrass. Sagebrush is unable to successfully recolonize when fires occur in rapid succession. In areas where bunchgrasses have been removed due to grazing, little remains following frequent fires except cheatgrass and annual species.

Primary goals for shrub-steppe conservation include: prevention of habitat loss through conversion; reduction of disturbance activities in unconverted habitat; and restoration of key habitat areas to dominant native species. Shrub-steppe conservation is currently a WNPS priority.