Shrub encroachment impacts the potential for multiple use conflicts on public land

Area of Science:

• Rangeland Ecology
• Vegetation Management
• Conservation Biology

Background:

• Public rangelands in North America are managed for multiple uses, including livestock grazing and wildlife support.
• Grassland ecosystems face threats from shrub encroachment, impacting biodiversity and forage availability.
• Maintaining range health is crucial for sustainable land management.

Purpose of the Study:

• To quantify grassland loss to shrub encroachment in southwestern Alberta, Canada.
• To assess the implications for livestock and wildlife populations.
• To evaluate the impact on overall range health.

Main Methods:

• Digitized aerial photographs from 1958, 1974, and 1998 were used for landscape analysis.
• Unsupervised classification and GPS-guided calibration-validation refined vegetation mapping.
• Grazing capacity was quantified using forage production data for grass and shrublands.

Main Results:

• Open grasslands decreased by 58% (1,111 ha to 465 ha) between 1958 and 1998.
• Total grazing capacity declined by 39% (2,744 Animal Unit Months), with a 58% reduction in grassland forage.
• Shrubland provided limited offset (1,357 AUMs) to the forage loss.

Conclusions:

• Shrub encroachment has significantly reduced forage, challenging the conservation of remaining grasslands.
• Continued habitat change threatens grassland health and may necessitate ungulate population reductions.
• Arresting shrub encroachment or initiating grassland restoration is critical for long-term sustainability.