Conservation Targets: Planning for Biodiversity
When the job is conserving a single threatened or endangered species, the focus
of planning is clear: Maintain the current population(s) or the meta-population.
Similarly, conserving a wetland ecosystem is fairly straightforward: Maintain the
current condition, prevent encroachment and limit sediment and pollutants from
entering the system. However, when one is given the task of conserving the biodiversity
on an installation, the challenges mount up fast. Experience has shown
managers the importance of identifying a limited number of conservation targets
on which to focus planning and management efforts; you cannot plan for everything
A common recommendation is that
planning teams use a coarse-filter/
fine-filter approach to identifying planning
targets. First, teams should focus
on the selection of ecological communities
or systems as conservation targets
at the onset. These act as the
"coarse-filter" targets (Noss and Cooperrider
1994, Poiani et al. 2000).
Teams should then add those species
with unique ecological requisites, not
already captured by the conservation
of those communities, or ecological
systems in which they are embedded.
The combined suite of species, community,
and ecological system targets
preferably a small and practical
number must collectively create a
safety net, such that their conservation
will help ensure that suitable environmental
conditions exist for the
persistence of all native species within
a landscape, installation or protected
area. Often, even though there are
many species and communities of interest,
most can be flagged as nested
targets: those that we expect will respond
Biodiversity conservation targets are a limited number of species, natural communities,
or entire ecological systems that natural resources managers select to represent the biodiversity of a conservation landscape or protected area, and that
therefore serve as the foci of conservation investment and measures of conservation
effectiveness. Thus, conservation targets are simply those ecosystems,
communities, or species upon which we focus planning and management efforts.
Because we use only a handful of targets to plan for biodiversity conservation,
selecting the appropriate suite of targets is crucial to successful conservation
planning and adaptive management. The reasoning behind such use of limited
elements of focal biodiversity is richly addressed in the literature (see for example
Noss and Cooperrider 1994, Christensen et al. 1996, Schwartz 1999, Poiani
et al. 2000, Carignan and Villard 2002, Sanderson et al. 2002).
PRIORITIES FOR MANAGEMENT ATTENTION
Conserving a species or ecosystem is more than simply ensuring its presence on
site. The overarching goal is really to ensure that those conservation targets are
currently, and will continue to be "healthy," or to continue to have integrity. Ecological
integrity is defined here as the ability of an ecological system to support
and maintain an adaptive community of organisms, having the species composition,
diversity, and functional organization comparable to that of natural habitats
within a region (Karr and Dudley 1981). An ecological system has integrity,
or a species is viable, when its dominant ecological characteristics (e.g., elements
of composition, structure, function, and ecological processes) occur within their
natural ranges of variation, and can withstand, and recover from, most perturbations
imposed by natural environmental dynamics or human disruptions. Effective
conservation occurs when the integrity of the ecological systems is maintained.
The keystone of effective conservation, then, is managing those factors,
or attributes, that are absolutely key to the target's persistence.
To identify what is most important to manage for the conservation of biodiversity
in protected areas on military installations, we must first synthesize our
best understanding of the ecology of the conservation target a process greatly
aided by the development of ecological models. An ecological model for a species, community, or ecological system will identify a limited number of biological characteristics,
ecological processes, and interactions with the physical environment
along with the critical causal links among them that distinguish the target from
others, shape its natural variation over time and space, and typify an exemplary,
reference occurrence (Maddox et al. 1999). Some of these characteristics will be
especially pivotal, influencing a host of other characteristics of the target and its
long-term persistence. Such defining characteristics of a target are labeled as "key
ecological attributes" (see Figure 2.3).
To illustrate, consider a riparian ecosystem situated within the foothills of a
montane ecoregion. One can identify enormous suites of species and describe numerous
biotic and abiotic interactions that typify this system. The magnitude,
spatial extent, timing, and duration of a snowmelt-fed, spring flooding may play
a pivotal role in a cascade of biological dynamics such as seed dispersal for native
riparian vegetation, variation in soil composition and fertility, elimination of
invasive species that compete with native species, and patterns of succession. If
so, the spring flooding regime would qualify as a key ecological attribute of this
ecosystem. Of course, the timing, duration, and intensity of these spring flood events differ (often dramatically) among years, and also respond to longer term
The Nature Conservancy's Measures of Success framework rests on the premise that
it is these "key ecological attributes" that must be managed and conserved to sustain
each conservation target. By explicitly identifying such attributes, managers
of protected areas can specify more concretely what is important to manage and
monitor about individual conservation targets, and, through them, assess conservation
success. Together, conservation targets and their key ecological attributes
become the essential currency for conservation management at any scale.
The key ecological attributes of any conservation target are many. They include
those of not only its biological composition and crucial patterns of variation in its
composition over space, but also the biotic interactions and processes, including
disturbance and succession dynamics, environmental regimes and constraints,
again including disturbance dynamics, and attributes of landscape structure and
architecture that sustain the target's composition and its natural dynamics (Noss
1990, 1996, Noss et al. 1995, Christensen et al. 1996, Schwartz 1999, Poiani et al.
2000, Young and Sanzone 2002). Identifying key attributes that address more than
just biotic composition is important for two reasons. First, the abundance and
composition of a target may lag in their responses to environmental impairments;
and data on biotic interactions, environmental regimes, and landscape structure
can help ensure the early detection of threats and change resulting from human
activities. Second, conserving only those targets on which we focus our planning
is not the ultimate goal but they are a means for conserving all native biodiversity
in an area. Consideration of these additional types of key ecological attributes will
further ensure that crucial aspects of ecological integrity are managed for the conservation
of all native biodiversity.
Key attributes of a target's biological composition and its spatial variation will
differ depending in part on whether the target is an individual species, an assemblage
of species, or a natural community, or an ecological system. This category
includes attributes of the abundance of species and the overall spatial extent
(range) of the target. Noss (1990) and Karr and Chu (1999) summarize the types
of key attributes of composition that are relevant to these different scales of biological
organization. Key biotic interactions and processes are those that significantly
shape the variation in the target's biological composition and its spatial
structure over space and time. These may include not only interactions among
specific species and functional groups, but also broad ecological processes that
emerge from the interactions among biota and between biota and the physical environment.
Examples include productivity, nutrient cycling, distribution of biomass
among trophic levels, biological mediation of physical or chemical habitat,
and the potential for trophic cascades (e.g., Pace et al. 1999, Scheffer et al. 2001).
Key environmental regimes and constraints, including their "normal" and extreme
variation, are those that shape physical and chemical habitat conditions,
and thereby significantly shape the target's biological composition and structure
over space and time. Examples include attributes of weather patterns, soil moisture
and surface- and groundwater regimes, fire regimes, water circulation patterns
in lakes, estuaries, and marine environments, soil erosion and accretion, and
geology and geomorphology. Key attributes of landscape structure and architecture
form a special subset of environmental constraints that include connectivity
and proximity among both biotic and abiotic features of the landscape at different spatial scales (e.g., Holling 1992). Such constraints, for example, affect the
ability of that landscape to sustain crucial habitat requirements in individual
species and the processes that transport habitat-forming matter (nutrients, sediment,
plant litter) across the landscape, and permit re-colonization of disturbed
locations and demographic sinks.
Thus, biodiversity conservation requires a winnowing of a relatively few key
components a.k.a. conservation targets from the universe of possible options
within the installation. The integrity, or viability, of each of these targets is defined
by identifying those attributes that contribute to the target's persistence. Thus, a
team that is planning for conservation at an installation could follow the following
sequence to identify its targets for planning:
- List those species explicitly identified for conservation, including those threatened
and endangered and other listed species that require protection.
- List the natural communities and ecosystems (coarse filter targets) located on
- Nest the species within the coarse filter targets, as much as possible.
- Aggregate the coarse filter targets, as appropriate vis-à-vis land management.
For example, pocket wetlands (small constructed systems, usually designed to aid
in stormwater control) may be most effectively managed as part of the larger upland
- Determine those species that are not captured and assess whether they require
special attention, including wide-ranging species.
- Finalize the list of targets to be the minimum sufficient set to capture all required
species, and important systems.
Proceed to Next Section: Assessing Threats to Biodiversity