Biological Opinions - Bureau of Reclamation

stratum 4 (Interior Klamath) in which the affected PCEs or essential features are found, and then
the overall designated area of critical habitat at the ESU scale. The basis of the analysis is to
evaluate any appreciable reduction to the function and role of the critical habitat in the
conservation of the species.
In this step of the assessment, NMFS identifies or makes assumptions about (a) the habitat’s
probable condition as the point of reference; (b) the ecology of the habitat at the time of
exposure; (c) where the exposure is likely to occur; (d) when the exposure is likely to occur; (e)
the expected intensity of exposure; (f) the likely duration of exposure; and (g) the frequency of
exposure. NMFS recognizes that the conservation value of critical habitat, like the base
condition of individuals and populations, is a dynamic property that changes over time in
response to the environment (e.g., changes in land use patterns, climate (at several spatial scales),
ecological processes, and changes in the dynamics of biotic components of the habitat). For
these reasons, some areas of critical habitat in the action area might respond to an exposure when
others do not. NMFS also considers how designated critical habitat is likely to respond to any
interactions and synergisms between or aggregate effects of pre-existing stressors and anticipated
project-related stressors.
As with the outline of the summary approach to how NMFS analyzes the effects from the
proposed action on individuals, NMFS performs the following steps to help determine effects
from the proposed action on designated critical habitat:
• Determine the critical habitat likely to be exposed to project-related stressors,
• Determine the area or features of critical habitat that could be affected by the proposed
project,
• Determine which PCEs or essential features could be affected by project-related stressors,
• Estimate the stressor(s) frequency, intensity, and duration of exposure to critical habitat,
• Determine if there will be interactions between existing stressors and project stressors on
critical habitat,
• Determine short-term responses of critical habitat to project-related stressors,
• Determine long-term responses of critical habitat to project-related stressors,
• Determine if the stressor and exposure scenarios anticipated are expected to result in an
appreciable reduction in the quantity, quality, or function of critical habitat in the action
area
If the quantity, quality, or availability of the PCEs or essential features of the area of designated
critical habitat are reduced, NMFS evaluates if those reductions are likely to be sufficient to
reduce the current conservation value of the designated critical habitat for listed species in the
action area. In this step of the assessment, NMFS combines information about the contribution
of PCEs or essential features of critical habitat to the conservation value of those areas of critical
habitat that occur in the action area, given the physical, chemical, biotic, and ecological
processes that produce and maintain those PCEs or essential features in the action area. NMFS
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In cases where the extent of designated critical habitat is smaller than the boundaries of a defined area such as a
diversity stratum, our analysis would focus on the extent of the designation within that area and not artificially
extend critical habitat boundaries.
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