Exotic Annual Grass Invasion

Invasion of cheatgrass and other exotic annual grasses, such as medusahead and ventenata, arguably represents the single-largest threat to America’s sagebrush rangelands, reducing forage productivity and carbon storage, and threatening wildlife habitat and rural economies. WLFW’s Framework seeks to defend relatively uninvaded sagebrush cores from annual grass conversion and expand them through restoration to maintain productive working lands that are resilient to fire and resistant to invasive annuals.

Strategic Approach

WLFW’s approach for tackling this threat relies on statewide maps identifying large, intact core areas with relatively low, or no, annual grass invasion. Core areas serve as anchor points for conservation action and inform a proactive strategy for management: Defend the Core, Grow the Core, Mitigate Impacts. For more information on how to apply this strategy, view this technical video:


Spatial Data

The maps below enable practitioners to rapidly visualize and analyze opportunities for threat reduction. Local maps and data should also be incorporated, where available, to refine conservation delivery.

  1. Annual Herbaceous Cover. This map depicts the estimated percent cover of herbaceous annuals on rangelands across the sagebrush biome. It was derived by combining three large-scale datasets to provide land managers a recent (2016-2018) estimate of the extent of invasive annuals. It can be used for identification of relatively uninvaded core areas for proactive management. More details on this product available here. Map of
annual herbaceous cover.

  2. Ecosystem Resilience and Resistance. This map provides a tool for rapid risk assessment across the range of sage-grouse using an index of sagebrush ecosystem resilience to disturbance and resistance to cheatgrass (“R&R”). It was derived using soil temperature and moisture data to depict underlying abiotic conditions that influence R&R. It can be used to assess relative recovery potential after disturbance and inform the level of restoration intervention that may be needed. More details on this product available here. Map of ecosystem resilience and resistance.

  3. RAP Vegetation Cover. These maps provide annual percent cover estimates from 1984 to present of: annual forbs and grasses, perennial forbs and grasses, shrubs, trees, and bare ground. The data can be used to assess biotic conditions to inform management actions and monitor vegetation through time. Annual forb and grass maps provide a useful surrogate for exotic annuals, allowing managers to understand fluctuations through time and track management outcomes. Perennial forb and grass maps can help managers determine if restoration seeding is needed following disturbance or annual grass control. More details on this product available here. Map of annual
cover.

  4. RAP Biomass. These maps provide annual and 16-day aboveground biomass from 1986 to present of: annual forbs and grasses, perennial forbs and grasses, and herbaceous (combination of annual and perennial forbs and grasses). Estimates represent accumulated new biomass throughout the year or 16-day period and do not include biomass accumulation in previous years. The data can be used to assess fine fuels affecting fire cycles and forage availability. Annual forb and grass maps provide a useful surrogate for exotic annuals, allowing managers to understand fluctuations through time and track management outcomes. More details on this product available here. Map of
annual biomass.