MegaLinkages, Wildlands Network Designs, and the Three-Track Approach to Conservation Planning.

March 2005

Mission and MegaLinkages

The mission of the Wildlands Project is to restore and protect the natural heritage of North America. To achieve this end we focus our efforts on four continental-scale "MegaLinkages"  that, when implemented, will tie North American ecosystems together for native species in their natural patterns of range and abundance:

1. Pacific MegaLinkage, along the west coast from Baja California to Alaska;
2. Spine of the Continent MegaLinkage, from Mesoamerica to Alaska through the Rocky Mountains and other ranges;
3. Atlantic MegaLinkage, from Florida to New Brunswick, mostly along the Appalachians;
4. Boreal MegaLinkage, from Alaska to The Canadian Maritimes across the roof of North America.

Each MegaLinkage is comprised of several "Wildlands Network Designs," science-based conservation plans that use cutting-edge research to identify areas of high biological value for very large regions. A typical wildlands network covers tens of millions of acres, ecologically reconnecting habitat across county, state, and international borders. Several network designs within the Spine of the Continent MegaLinkage (454 k) have been completed and the first network design for the Atlantic MegaLinkage, the greater Northern Appalachians (367 k), will be completed in 2005.

Why Large-Scale Conservation?

But why do we need to focus conservation on such a large scale? "Global biodiversity is changing at an unprecedented rate as a complex response to several human-induced changes in the global environment. The magnitude of the change is so large and so strongly linked to ecosystem processes and society's use of natural resources that biodiversity change is now considered an important global change in its own right (Sala et al. 2000)."

Major global change is occurring in:

• land use
• climate change
• nitrogen deposition and acid rain
• invasive and exotic species (sometimes called "biotic exchange")
• atmospheric CO2 concentration

Over the next 100 years land use change will have the most dramatic impacts on biodiversity in terrestrial habitats, while biotic exchange will likely be most important in freshwater ecosystems (Sala et al. 2000).

Moreover, in North America - and world-wide - existing systems of protected areas are not doing a good job of conserving the full sweep of biodiversity. Recent assessments show that less than 6% of the coterminous United States is in nature reserves and that most reserve are found at higher elevations and on less productive soils, even as the greatest number of plant and animal species are found at lower elevations. Analyses of land cover types indicate that approximately 60% of mapped cover types have less than 10% of their area in nature reserves. Land ownership patterns show that areas of lower elevation and more productive soils are most often privately owned and already extensively converted to urban and agricultural uses (Scott et al. 2001).

Another recent study (Andelman and Willig 2003) illustrates the skewed geographical and size distributions of protected areas in the Western Hemisphere: 811 of 1413 reserves in the Western Hemisphere are smaller than 10 km2, and 35% of the total area of these reserves is in Alaska. This study compiled information on the ranges of all bats in the continental New World (such data are not available for all taxa): 82% of threatened and small-range species are not protected adequately. Many of the most vulnerable species occur in the areas of highest human density.

North America has also lost many of its native predators in large parts of their historic ranges. Wide-roaming carnivores like wolves and jaguars often play essential roles in regulating the numbers and behavior of prey species below them in food chains. Such food chains are woven into complex webs of interaction, and the loss of large carnivores can reverberate through these webs, causing the local disappearance of species and even entire communities (Soulé et al. 2005; Soulé et al 2003; Terborgh et al. 1999; Soulé and Noss 1998; Estes et al. 1978; 1998; Henke and Bryant 1999; Rogers and Caro 1998; Kullberg and Ekman 2000; Power et al. 1996). In much of North America, for example, white-tailed deer and raccoons have become overabundant in the absence of their predators, disrupting plant communities and eliminating some kinds of birds and small mammals (McGraw and Furedi 2005; Waller and Alverson 1997; DeCalesta 1994; McShea and Rappole 1997 Cederlund and Sand 1991; Crête and Manseau 1996).

Despite these critical issues, much past conservation has been ad hoc, often driven by a region's scenic values or remoteness-as well as wildlife and natural values. But this "approach to biological conservation has left Canada, the United States, Mexico, and most other countries with highly fragmented systems of parks and reserves in which some elements of the native biota are overrepresented and others are not represented at all (Soulé and Terborgh 1999b)." The fact that this has occurred not only in North America but throughout the world was acknowledged by Margules and Pressey (2000) in their landmark paper on systematic conservation planning.

There is broad consensus, then, that the fundamental solution to these problems lies in establishing, in a systematic fashion, large core reserves of wild habitat within entire regions. But even large wilderness cores are not enough; to facilitate the flow of life across the entire landscape, these cores must be linked by corridors of wild habitat that allow the unimpeded movement of wildlife and natural processes such as wildfire and spring floods. These interconnected wildlands also need to be buffered from ecologically destructive human activities by areas of compatible use-often called stewardship lands-where low-impact farming and forestry complement the functions of the core areas (Trombulak 2001; Trombulak 2003; Noss and Cooperider 1994). The result is a network of core wild areas, functionally linked across the landscape and buffered by well-managed stewardship lands.

What is the most efficient means of creating networks of reserves? There is good agreement within the conservation community that planning and action should adhere to four key principles:

• Establish planning boundaries based on ecological features
• Set clear biodiversity conservation goals within a given planning boundary
• Follow a systematic conservation planning process
• Involve a broad array of stakeholders in design and implementation

Establish planning boundaries based on ecological features

MegaLinkages represent the first step of establishing boundaries based on ecological features: in this case the major mountain and boreal regions of North America. The network designs within the MegaLinkages should then adhere to further ecological subdivisions. Since the mid-1990s there has been broad agreement among conservation scientists as to the definitions, boundaries and utility of these ecological divisions, usually referred to as ecoregions (Bailey 1998, 2002; Olson et al. 2001). As Olson et al. (2001) observe: "conservation strategies that consider biogeographic units at the scale of ecoregions are ideal for protecting a full range of representative areas, conserving special elements, and ensuring the persistence of populations and ecological processes, particularly those that require the largest areas or are most sensitive to anthropogenic alterations (Noss et al. 1999; Soulé and Terborgh 1999a; Groves et al. 2000; Margules and Pressey 2000)".

Set clear biodiversity conservation goals within a given planning boundary

There is also broad agreement among conservation biologists as to the operational goals necessary for the protection and restoration of life (Noss and Cooperider 1994; Trombulak 2001):

• Represent all native ecosystem types and stages
• Maintain viable populations of all native species in natural patterns of abundance and distribution
• Maintain ecological and evolutionary processes
• Design and manage system to be responsive to change

As Trombulak (2001) observes: "taken together, these goals encompass all of the levels of the biological hierarchy: genes (through an emphasis on viable populations, since viability is associated with genetic diversity), species, and communities. Further, these goals encompass all three dimensions of biological organization: composition, function, and structure. The composition of biological communities is incorporated by the focus on all natural community types and species, structure by the focus on the full range of successional stages, and function by the focus on processes and adaptability."

Follow a systematic conservation planning process

Following the principles advanced by Noss (2003) and Margules and Pressey (2000), the Wildlands Project's conservation plans feature explicit conservation goals, quantitative ecological features or "targets," rigorous methods for locating new reserves to complement existing ones, and explicit criteria for implementing conservation action (Figure 1).

Specifically, the current Wildlands Project methodology integrates three general approaches to conservation planning that, in the past, usually have been applied separately:

1. Representation of habitats - inclusion of a full spectrum of habitat types (e.g., vegetation, abiotic habitats, aquatic habitats) in protected areas or other areas managed for natural values;

2. Mapping of special elements - identifying and mapping rare species occurrences (and particularly "hotspots" where occurrences are concentrated), watersheds with high biological values, imperiled natural communities, and other sites of high biodiversity value;

3. Modeling of habitat requirements and population viability of focal species - identifying key habitats of wide-ranging species and others of high ecological importance or sensitivity to disturbance by humans.

Focal Species Modeling

The most innovative feature of the three-track approach is the rigorous modeling of habitat requirements and population viability of wildlands-associated focal species, such as large carnivores and forest mesocarnivores (Miller et al. 1998, Carroll et al. 2001, Noss et al. 2002).

Given the disproportionately strong influence on ecosystem functioning and diversity of these predators, it is critical to understand their population structure and viability and the distribution of suitable habitats on a given landscape (Soulé and Noss 1998 382 k). "Because many carnivores have demanding area requirements and occur in low densities, their viability much be considered over enormous areas (Noss 2002)." It is also important to consider the "ecologically effective" population levels of these species - that is, the "population level that prevents undesired changes in a defined ecological setting (Soulé et al. 2005)."

As discussed above, keystone species, which have a disproportionately strong influence on ecosystem functioning and diversity (Power et al. 1996), are also suitable focal species, especially when the goal is to maintain their populations at ecologically effective levels (Soulé and Noss 1998).

Elimination or even significant declines of these species may lead to cascades of direct and indirect changes on more than a single trophic level, ultimately leading to significant losses of biodiversity (Terborgh et al. 1999). In Yellowstone, extirpation of wolves in the early 1900s allowed elk and other ungulates to graze aspen shoots so heavily that very few shoots were recruited into the overstory after the 1920s (Ripple and Larsen 2000). Elk browsing also stopped recruitment of cottonwood and willow in riparian areas, which in turn caused the local disappearance of beaver wetlands. The reintroduction of wolves in 1995 has almost certainly reversed these effects (Ripple and Beschta 2004; Beschta 2003).

The carnivores used as focal species fall into the area-limited and, in some cases, the dispersal-limited categories of focal species suggested by Lambeck (1997).The most sensitive species in these categories are assumed to serve as umbrellas for other species with less demanding spatial requirements. Other focal species that may serve umbrella functions include resource-limited species, sensitive to the availability of resources, and process-limited species, sensitive to the frequency, intensity, extent, or timing of natural processes such as disturbance (Lambeck 1997).

Focal species analysis complements the special elements and representation tracks by addressing questions concerning the size and configuration of reserves and other habitats necessary to maintain populations over time. The focal species approach can be distinguished from the species component of the special elements track, in that habitat suitability and population viability are modeled and extrapolated beyond current, known occurrences and, often, beyond the present time. In contrast, special elements mapping is a static portrayal of documented occurrences of species, usually represented as points, lines (e.g., for aquatic taxa), or polygons.

There are a number of techniques available to help determine the size and configuration of habitat. A key tool is the static habitat suitability model, which provides a snapshot in time of habitat conditions relative to a species' requirements. "These models can be used to predict which parts of a landscape are most favorable for a species but tell us little about how long a population might persist there. We are now realizing the utility of dynamic population models, which predict habitat occupancy and rate of population growth of a species over time. The dynamic models begin with data on habitat quality from the static models and then builds on this information by simulating the birth, dispersal, reproduction, a death of individuals throughout a study region based on what is known about the life history of the species. Thus the dynamic model provides a population viability analysis (PVA), but unlike many PVAs, it is spatially explicit (Noss 2002)."

The Wildlands Project is applying static habitat suitability modeling of focal species, generally based on resource selection functions (Boyce and McDonald 1999) in all of its current designs, following the methods of Carroll et al. (2001). Moreover, the newest designs use an individual-based population model, PATCH (Schumaker 1998), to conduct dynamic modeling. PATCH links information on habitat suitability, corresponding to mortality risk and habitat productivity, to demographic information on each focal species. Therefore, likely population sources and sinks can be identified on a regional scale. The model tracks the population as individuals are born, disperse, and die and allows the landscape to change through time. Hence, predictions can be made concerning the consequences of landscape change for the population viability of each species (Noss et al. 2002). Wildlands Project has recently completed such models for wolf Wolf Viability (526 k), Impacts of Landscape Change on Wolf Viability (736 k), Lynx and Marten (1 MB).

The Site Selection Process

In its current round of network designs, Wildlands Project is applying a site-selection algorithm such as SITES (Andelman et al. 1999) or MARXAN (Ball and Possingham undated; www.ecology.uq.edu.au/index.html?page=20882 ) to select "planning units" that are ultimately aggregated into core areas (Noss et al. 2002). Planning units can be watersheds or some other regular shape. Recent experience suggests that hexagonal planning units are the best shape. To use the algorithm, a grid of hexagonal planning units is laid down over the planning area. Planning units are then "populated" with data on the focal species, representation, and special elements features (targets) that have been selected for planning area. A given planning area may be stratified into a number of smaller biophysical regions. For each strata a set of special element and representation targets is established. Focal species targets are generally established for the planning area as a whole

The algorithm minimizes costs of conservation by selecting the smallest overall area needed to meet specified conservation goals for given targets. Goals from the special elements, representation, and focal species targets are all stated quantitatively as input to these algorithms. Focal species can be considered, for example, by setting a goal of habitat sufficient to support x% of the current potential population of each species, as defined by the resource selection function (Noss et al. 2002).

Unlike many previous algorithms, which often neglected the configuration of sites and resulted in fragmented portfolios that are difficult to manage (Briers 2002; McDonnell et al. in press), the simulated annealing algorithms employed by SITES and MARXAN include a "boundary length modifier" which allows planners to achieve a compact design by clustering selected sites or placing them adjacent to existing protected areas (Andelman et al. 1999, Possingham et al. 2000). Nevertheless, the resulting "portfolio" of sites may still lack sufficient connectivity to provide for viable populations of focal species. Expert judgment is generally required to design a sufficiently-connected network. The PATCH model can greatly assist this judgment, however, by testing the ability of alternative reserve networks to maintain viable populations (Noss et al. 2002).

Site selection software also allows for the establishment and testing of multiple goal scenarios-different combinations of quantitative goals-and their effects on the size and placement of conservation areas.

Using the outputs from the site selection algorithm, a draft Wildlands Network Design can be created comprised of three basic components:

• core wild areas, where natural processes are allowed to direct the ebb and flow of life;
• wildlife linkages, zones of shared use by humans and wildlife that allow for the unimpeded migration of species, genes, and natural processes across the land; and
• compatible-use/stewardship areas, which surround and buffer core wild areas and support vibrant and sustainable rural economies

Involve a broad array of stakeholders in design and implementation

It is critical to involve regional stakeholders, scientific and otherwise, in the process of designing and implementing a network design. The draft network design should undergo a series of rigorous expert reviews before a final design is released. This process is guided by the Scientific Advisory Committee, a core group of committed scientists who are familiar the region or with the Wildlands Project's scientific methods, who can guide and direct necessary research, fieldwork, and data collection by staff, interns, and volunteers. At the same time, we work closely with our partners to integrate the network design process with local and regional efforts to identify and protect conservation areas.

This entire systematic planning process, as adapted by the Wildlands Project, has been condensed into "A Checklist for Wildlands Network Designs" (Noss 2003).

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