22
An Overview of Ecological Assessment Principles and Applications
TABLE 1.3. A generalized description of the scales used in ecological assessments.
Traditional
planning
scales'
Assessment
scale
Typical
analysis area
size (sq. mi.)
Typical issues
Continental
>10,000
N eotropical birds
Climate change
National timber supply
Regional
1000--10,000
Widely distributed species (salmon,
Regional
guides
grizzly bear)
Roadless areas
Wildernesses
River basin health
Subregional
10-1000
Old growth
Forest plans
Landscape
1-10
Area plans
Land unit
Project plans
Site
<1
River subbasin health
General fIre management needs
Timber volumes
Watershed health
Vegetation pattern (cover type and
structural stage)
SpecifIc fIre management needs
Soil compaction
Specific vegetation management design
Vegetation regeneration
Small mammal activity
'A given level of planning requires complete spatial representation of information at the assessment level above, and subsampled
information at the level(s) below.
bResource Planning Act
adequately addressed in previous land allocation
or regulation strategies. These issues commonly
require that different spatial scales of assessment be utilized in the planning process; they
tend to be broader in scope and require a larger
geographic context for their resolution.
3. Significant change occurs to the ecosystem.
When unexpected significant change occurs to
an ecosystem, management goals and objectives
for the system must be reevaluated. Such catastrophic changes are referred to as surprise
events by Holling (1978) and can be better predicted through monitoring programs designed to
account for uncertainty. Large-scale fire is an
example of a significant ecosystem process that
can greatly alter the vegetation patterns of an
area. If such process-pattern relations are not
explicitly addressed in planning documents, integrated ecological assessments may be triggered by such surprise events.
1.4.2 Information Needs
A wide variety of information can and must be used
in an integrated ecological assessment. It is important, however, that the information utilized correspond directly to the purpose and need for the assessment. The first step in the assessment process,
therefore, should be the identification of the major
policy questions or issues to be addressed (see
Table 1.2).
Once the policy questions or issues for the assessment are identified, they are further examined
to select appropriate scales of analysis (Table 1.4).
Climate change, for example, is a process that is
meaningfully addressed at broader assessment
scales. Grizzly bear viability assessments, by contrast, commonly assess conditions within the home
range area of the species (i.e., the regional or subregional scale). Soil erosion assessments are commonly related to patterns of soil bodies as they occur on landforms, which are usually displayed at
landscape or land unit levels of assessment.
Another critical step in the assessment process is
the identification of scale-specific, measurable, and
mappable features that relate to the issues being addressed. Techniques for pattern recognition (Jensen
et al., 1996) are particularly useful because they require concise description of the hierarchical relations between the pattern of interest and the agents
of its formation (Le., biophysical environments, disturbance regimes, and biotic processes). For exam-
An Overview of Ecological Assessment Principles and Applications
TABLE 1.3. A generalized description of the scales used in ecological assessments.
Traditional
planning
scales'
Assessment
scale
Typical
analysis area
size (sq. mi.)
Typical issues
Continental
>10,000
N eotropical birds
Climate change
National timber supply
Regional
1000--10,000
Widely distributed species (salmon,
Regional
guides
grizzly bear)
Roadless areas
Wildernesses
River basin health
Subregional
10-1000
Old growth
Forest plans
Landscape
1-10
Area plans
Land unit
Project plans
Site
<1
River subbasin health
General fIre management needs
Timber volumes
Watershed health
Vegetation pattern (cover type and
structural stage)
SpecifIc fIre management needs
Soil compaction
Specific vegetation management design
Vegetation regeneration
Small mammal activity
'A given level of planning requires complete spatial representation of information at the assessment level above, and subsampled
information at the level(s) below.
bResource Planning Act
adequately addressed in previous land allocation
or regulation strategies. These issues commonly
require that different spatial scales of assessment be utilized in the planning process; they
tend to be broader in scope and require a larger
geographic context for their resolution.
3. Significant change occurs to the ecosystem.
When unexpected significant change occurs to
an ecosystem, management goals and objectives
for the system must be reevaluated. Such catastrophic changes are referred to as surprise
events by Holling (1978) and can be better predicted through monitoring programs designed to
account for uncertainty. Large-scale fire is an
example of a significant ecosystem process that
can greatly alter the vegetation patterns of an
area. If such process-pattern relations are not
explicitly addressed in planning documents, integrated ecological assessments may be triggered by such surprise events.
1.4.2 Information Needs
A wide variety of information can and must be used
in an integrated ecological assessment. It is important, however, that the information utilized correspond directly to the purpose and need for the assessment. The first step in the assessment process,
therefore, should be the identification of the major
policy questions or issues to be addressed (see
Table 1.2).
Once the policy questions or issues for the assessment are identified, they are further examined
to select appropriate scales of analysis (Table 1.4).
Climate change, for example, is a process that is
meaningfully addressed at broader assessment
scales. Grizzly bear viability assessments, by contrast, commonly assess conditions within the home
range area of the species (i.e., the regional or subregional scale). Soil erosion assessments are commonly related to patterns of soil bodies as they occur on landforms, which are usually displayed at
landscape or land unit levels of assessment.
Another critical step in the assessment process is
the identification of scale-specific, measurable, and
mappable features that relate to the issues being addressed. Techniques for pattern recognition (Jensen
et al., 1996) are particularly useful because they require concise description of the hierarchical relations between the pattern of interest and the agents
of its formation (Le., biophysical environments, disturbance regimes, and biotic processes). For exam-