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 in isolation.

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 climatic changes.

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 the installation.
• 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 matrix.
• 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