1.4 General Properties of an Ecological Assessment
tion of using aggregate data or models is that, by
integrating many fine-level details, the data or models may not represent ecosystem behavior at the appropriate spatiotemporal scale (see discussion in
Costanza et aI., 1993, on aggregate models and
ecological processes; also see Hofmann, 1991).
Costanza and Maxwell (1994) discuss the relationship between level of resolution and predictability.
They found that increasing resolution provides
more information about the patterns in data, but
also increases the difficulty of accurately modeling
these patterns. These authors also found that predictability exhibits fractallike characteristics with
decreasing resolution.
How are these findings relevant to ecological assessments? Knowing that predictability in explaining a particular pattern increases with resolution,
whereas predictability in modeling the pattern decreases, an optimal resolution may be defined for
a particular problem. For example, forest response
to beetle outbreaks may exhibit chaotic dynamics
at the level of a National Forest, but be more predictable at the continental level. Indeed, Sugihara
and May (1990) found that measles epidemics
show chaotic dynamics at the level of individual
cities, but more predictable periodic dynamics for
entire nations. This example reinforces the point
that data used across spatial scales must be analyzed carefully in terms of a particular problem:
there are limits to the predictability of natural phenomena, and assessment protocols should reflect
this fact.
Predictability of ecosystems also is complicated
when the processes that historically have created
heterogeneity in landscape patterns are altered, resulting in new and unprecedented landscape patterns (see the previous discussion of fire regimes
and Figure 1.2). Quantification of ecosystem stability and resiliency is extremely difficult under
such conditions. Consequently, any predictions
concerning highly altered ecosystems should be
monitored closely under an adaptive management
process (Lessard et aI., 1999).
1.4 General Properties of an
Ecological Assessment
1.4.1 Purpose
To reiterate, ecological assessments are an important component of any strategy for implementing
ecosystem-based management (Slocombe, 1993;
Jensen and Bourgeron, 1994). Furthermore, hierarchy theory suggests that ecosystems may be de21
scribed at different spatial scales and that levels of
ecosystem organization at broader scales bound the
range of ecological properties that emerge at finer
scales (Allen and Starr, 1982; Allen et aI., 1984;
O'Neill et aI., 1986; Bourgeron and Jensen, 1994).
Accordingly, ecological assessments should be
conducted at multiple spatial scales (Table 1.3) to
improve our understanding of the relations between
different ecosystem components most appropriately addressed at different scales (e.g., vegetation
biomes, plant communities, rare species).
Broad-scale ecological assessments facilitate
better land management decisions by placing more
localized ecosystem management strategies into
proper context. Regional assessments of mature
forest patterns, for example, can greatly assist the
development of management plans for old-growth
forest networks, which in tum can be used to help
to direct local timber sale activities. Strategies of
landscape design directed toward desired ecological condition objectives for management are best
framed within a multiscale ecological assessment
process. In this approach, desired ecological conditions are defined at different scales dependent on
the specific issues at hand. Design objectives identified at broader scales are incorporated into management strategies for smaller ecosystems to ensure that activities at more localized levels are
consistent with the larger plan. Multiscale ecological assessments enable decisions to be made from
scale-appropriate information, and they place allocation and regulation decisions into the proper biophysical and social context, hence contributing to
improved management decisions.
Ecological assessments are commonly conducted when major land management or regulatory
decisions need to be reevaluated. The need for an
ecological assessment should be identified through
ongoing monitoring efforts based on one or more
of the following changes:
1. Initial assumptions change as new knowledge is
obtained. Implicit in this statement is an awareness that our understanding of ecosystem composition, structure, and function is, more often
than not, incomplete. Given this fact, it is often
necessary to revisit management decisions as
our understanding of ecosystem interactions improves.
2. Social values and needs change. As new issues
are identified by various sectors of the public,
different scales of analysis are often required.
Climate change, forest health, and biodiversity
are examples of issues that have recently
achieved high-profile status and often were not
tion of using aggregate data or models is that, by
integrating many fine-level details, the data or models may not represent ecosystem behavior at the appropriate spatiotemporal scale (see discussion in
Costanza et aI., 1993, on aggregate models and
ecological processes; also see Hofmann, 1991).
Costanza and Maxwell (1994) discuss the relationship between level of resolution and predictability.
They found that increasing resolution provides
more information about the patterns in data, but
also increases the difficulty of accurately modeling
these patterns. These authors also found that predictability exhibits fractallike characteristics with
decreasing resolution.
How are these findings relevant to ecological assessments? Knowing that predictability in explaining a particular pattern increases with resolution,
whereas predictability in modeling the pattern decreases, an optimal resolution may be defined for
a particular problem. For example, forest response
to beetle outbreaks may exhibit chaotic dynamics
at the level of a National Forest, but be more predictable at the continental level. Indeed, Sugihara
and May (1990) found that measles epidemics
show chaotic dynamics at the level of individual
cities, but more predictable periodic dynamics for
entire nations. This example reinforces the point
that data used across spatial scales must be analyzed carefully in terms of a particular problem:
there are limits to the predictability of natural phenomena, and assessment protocols should reflect
this fact.
Predictability of ecosystems also is complicated
when the processes that historically have created
heterogeneity in landscape patterns are altered, resulting in new and unprecedented landscape patterns (see the previous discussion of fire regimes
and Figure 1.2). Quantification of ecosystem stability and resiliency is extremely difficult under
such conditions. Consequently, any predictions
concerning highly altered ecosystems should be
monitored closely under an adaptive management
process (Lessard et aI., 1999).
1.4 General Properties of an
Ecological Assessment
1.4.1 Purpose
To reiterate, ecological assessments are an important component of any strategy for implementing
ecosystem-based management (Slocombe, 1993;
Jensen and Bourgeron, 1994). Furthermore, hierarchy theory suggests that ecosystems may be de21
scribed at different spatial scales and that levels of
ecosystem organization at broader scales bound the
range of ecological properties that emerge at finer
scales (Allen and Starr, 1982; Allen et aI., 1984;
O'Neill et aI., 1986; Bourgeron and Jensen, 1994).
Accordingly, ecological assessments should be
conducted at multiple spatial scales (Table 1.3) to
improve our understanding of the relations between
different ecosystem components most appropriately addressed at different scales (e.g., vegetation
biomes, plant communities, rare species).
Broad-scale ecological assessments facilitate
better land management decisions by placing more
localized ecosystem management strategies into
proper context. Regional assessments of mature
forest patterns, for example, can greatly assist the
development of management plans for old-growth
forest networks, which in tum can be used to help
to direct local timber sale activities. Strategies of
landscape design directed toward desired ecological condition objectives for management are best
framed within a multiscale ecological assessment
process. In this approach, desired ecological conditions are defined at different scales dependent on
the specific issues at hand. Design objectives identified at broader scales are incorporated into management strategies for smaller ecosystems to ensure that activities at more localized levels are
consistent with the larger plan. Multiscale ecological assessments enable decisions to be made from
scale-appropriate information, and they place allocation and regulation decisions into the proper biophysical and social context, hence contributing to
improved management decisions.
Ecological assessments are commonly conducted when major land management or regulatory
decisions need to be reevaluated. The need for an
ecological assessment should be identified through
ongoing monitoring efforts based on one or more
of the following changes:
1. Initial assumptions change as new knowledge is
obtained. Implicit in this statement is an awareness that our understanding of ecosystem composition, structure, and function is, more often
than not, incomplete. Given this fact, it is often
necessary to revisit management decisions as
our understanding of ecosystem interactions improves.
2. Social values and needs change. As new issues
are identified by various sectors of the public,
different scales of analysis are often required.
Climate change, forest health, and biodiversity
are examples of issues that have recently
achieved high-profile status and often were not