Research article summary (published 7 Jul 2009):

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

Full Abstract

Public rangelands in North America are typically managed under a multiple use policy that includes livestock grazing and wildlife management. In this article we report on the landscape level extent of grassland loss to shrub encroachment in a portion of the Rocky Mountain Forest Reserve in southwestern Alberta, Canada, and review the associated implications for simultaneously supporting livestock and wildlife populations while maintaining range health on this diminishing vegetation type. Digitized aerial photographs of 12 km of valley bottom from 1958 and 1974 were co-registered to ortho-rectified digital imagery taken in 1998, and an un-supervised classification used to determine areas associated with grassland and shrubland in each year. Field data from 2002 were over-layed using GPS coordinates to refine the classification using a calibration-validation procedure. Over the 40-year study period, open grasslands declined from 1,111 ha in 1958 to 465 ha in 1998, representing a 58% decrease. Using mean production data for grass and shrub dominated areas we then quantified aggregate changes in grazing capacity of both primary (grassland) and secondary (shrubland) habitats for livestock and wildlife. Total declines in grazing capacity from 1958 to 1998 totaled 2,744 Animal Unit Months (AUMs) of forage (-39%), including a 58% decrease in primary (i.e., open grassland) range, which was only partly offset by the availability of 1,357 AUMs within less productive and less accessible shrubland habitats. Our results indicate shrub encroachment has been extensive and significantly reduced forage availability to domestic livestock and wildlife, and will increase the difficulty of conserving remaining grasslands. Although current grazing capacities remain marginally above those specified by regulated grazing policies, it is clear that continued habitat change and decreases in forage availability are likely to threaten the condition of remaining grasslands. Unless shrub encroachment is arrested or grassland restoration initiated, reductions in aggregate ungulate numbers may be necessary.

Author information

Author/s: Burkinshaw, Angela M (AM); Bork, Edward W (EW);

Affiliation: Rangeland Management Branch, Alberta Sustainable Resource Development, #211 4920-51 Street, Red Deer, AB, Canada.

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: Environmental management (Environ Manage), published in United States. (Language: eng)

Reference: 2009-Sep; vol 44 (issue 3) : pp 493-504

Dates: Created 2009/08/12; Completed 2009/10/05;

PMID: 19588191, status: MEDLINE (last retrieval date: 10/5/2009, IMS Date: )

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Alberta Animals Animals, Domestic Animals, Wild Conservation of Natural Resources

Conservation of Natural Resources Ecosystem Environmental Monitoring Geographic Information Systems Poaceae

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