DoD Biodiversity Conservation Handbook
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Chapter 6: Managing for Threatened, Endangered, and Sensitive Species

Target Viability

The first step toward identifying threats to the focal targets is to generally assess their viability. Viability is based on three factors: size, condition, and landscape context.

The viability ranking process provokes thought and discussion that become the basis for assessing factors that threaten the status of the focal targets, and overall biodiversity in the planning area. Planners generally define those threats in terms of human behaviors and land uses that, if left unchanged, would adversely affect the targets in the conservation area.

Wildlife biologists at the Barry M. Goldwater Range, Arizona, carefully monitor for the presence of the endangered Sonoran pronghorn antelope. Air Force and Marine Corps operations can proceed on individual bombing ranges only if no antelope are detected within 15 kilometers. (Photo: Douglas Ripley)

Justification must be documented for each the rankings. For example, as shown in Table 6.2, the size of the woodland/savanna/shrubland target was ranked as fair because, although landscape patch size, or management unit size, is variable, some large units are under management. The condition for this target is rated as fair because, while highly diverse plant communities do exist in barrens restoration sites, the majority of this habitat type is the result of other management goals (i.e. silvicultural practices). Bird species diversity, however, remains high in most of these patches. The landscape context is ranked as poor because it occurs in a fragmented state, scattered across the base. Small patch size leads to increased nest parasitism and predation of breeding birds. In addition, lack of landscape connectivity prevents colonization by low mobility species (e.g., pine snake).

Proceed to Next Section: Threats: Stresses and Sources of Stress

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About This Chapter's Author
John Lamb is a conservation biologist.

Kevin Willis is a plant ecologist.

George R. Wyckoff is a wildlife ecologist at Arnold AFB, Tennessee.

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