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Making Connections for Wildlife Aligning Transportation Projects with State Wildlife Action Plans: A Step-by-Step Guide for Integrated Conservation Planning
Step Two: Identify and Map Wildlife
Linkages The development of a spatially explicit wildlife linkages data layer involves multiple steps, each of which is outlined below. Once complete, these data can be overlaid with spatial data on upcoming transportation projects in the STIP to highlight potential conflicts with wildlife. Researchers at While other tools and methodologies are also available and may be adapted to this process, we feel that the Corridor Design tool is the most appropriate for fine-scale mapping of wildlife linkages. Should your team elect to use a different analysis and mapping tool, you may still want to review the steps described in this section, as the general processes and considerations will remain similar regardless of the specific GIS methodology used. Link:
GIS Mapping Steps The following steps should be pursued in close collaboration and communication with the Partnership Team, so that all members of the team – biologists and non-biologists alike – fully understand and participate in the analysis process. These steps are described below, however, for more information, we highly recommend that you also consult the Corridor Design webpage (see link, above). GIS Mapping Step 1 – Identify Analysis
Area(s) Define what you are trying to connect. Identify and
prioritize core and linkage areas. Several states, including Links: Report: Inventory of States with Completed or In-Progress Connectivity Assessments GIS Mapping Step 2 – Compile List of Target
Species: Consider the following types of species:
In reviewing the selected suite of target species, make sure that the range of habitat types and ecological systems present within the analysis area are captured by the target species. GIS Mapping Step 3 – Define Habitat
Parameters and Compile Data Layers A number of parameters must be defined for each target species to conduct the corridor modeling. Parameter definition should be conducted in close collaboration with each species biologist. Review of the parameters by several biologists is recommended, whenever feasible, and keep in mind that the parameters may require tweaking through several iterations in order to develop appropriate models. There are four primary factors that are evaluated for each target species: land cover, elevation, topography, and distance from roads. Each of these criteria are weighted (0-100%), depending on the degree to which they influence a given target species’ habitat use. Each factor is given a percentage of its importance to the species so that the factors add up to 100%. The factors are then combined spatially to create the final HSM where every pixel has a value of the habitat importance to the species. Then, for each factor with a weight greater than zero the weighted geometric mean was calculated by raising each factor by its weight, and multiplying the factors. If a particular target species’ habitat use
cannot be adequately captured by these four factors, then the team
may want to consider adding a new factor for that species (e.g.,
aspect, soil type). However, the makers of the Corridor Design tool
argue, and we concur, that the use of few factors and few
categorical metrics within each factor is better than many factors
or numerous categories within a factor – complex models become
increasingly abstract and are likely to be poor representations of
what is actually occurring on the ground.
Other parameters that must be defined for each
target species include minimum core patch size and daily dispersal
distance. In addition, the team must determine how start and end
points for each linkage analysis will be determined. In The primary data layers needed for the Corridor Design Analysis include: land cover (reclassified to a smaller number of habitat groupings), digital elevation model (30m resolution), and roads. Additional data layers may be needed if other factors were identified as primary influences on a given target species’ habitat preferences. GIS Mapping Step 4 – Adapt Corridor Design
Tool The first step of adapting the Corridor Design tool is to define the areas of focus. More specifically, to identify areas where species are moving or potentially are moving through the landscape. Once the analysis area has been selected then the habitat suitability model can be clipped to the specific area for development of the habitat suitability model. The next step is to identify potential breeding patches and potential population cores. Potential breeding patches = areas large enough to support one breeding event for one season. Potential population cores = areas large enough to support a breeding population for approximately ten years. To create the Habitat Suitability Model (HSM) for each species, each analysis cell of the land cover data layer is weighted based on the habitat preferences as defined by the species experts (Fig. 2). Land
Cover Weights: 1-3 = strongly preferred (1 is best) 4-5 = usable but suboptimal habitat
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Suitability Threshold 6-7 = not breeding habitat, but occasionally used 8-10 = strongly avoided (10 is worst) The suitability of the habitat is evaluated such that areas above the habitat threshold (i.e., weighted < 5) are joined into polygons of suitable habitat. Core habitat patches are created by combining all suitable and unsuitable habitat that falls within the designated daily dispersal distance, such that unsuitable habitat within a matrix of suitable habitat may be included in a core habitat patch. Suitable habitat beyond the species’ dispersal distance is not included in a core patch. Each habitat patch is then evaluated based on its size, relative to the minimum patch size needed to support a breeding event and the minimum patch size needed to support a core population for at least ten years – habitat patches smaller than these minimums are not considered core habitat.
Figure 2:
Example of a Habitat Suitability
Model. Protected areas, species data on existing breeding populations or occupied habitat, or potential core habitat patches (derived from the HSM) are used to define the endpoints (actually areas) for the linkage analysis model. These endpoints define the area between which the linkage will be identified. The Corridor Design analysis is performed creating a cost surface based on the HSM (Fig. 3). This is similar to a least-cost path analysis, but also incorporates suitable habitat patch sizes (i.e., small, stepping-stone patches that are too small to be core habitat patches, but may still be important as animals move between core habitat patches) and the species’ daily dispersal distance threshold. The resulting movement surface is a gradation that demonstrates the difficulty (i.e., cost) of moving between the two identified endpoints.
Figure 3:
Example of a cost-surface. Based on this gradated movement surface, the next step is to determine an appropriate linkage width – this width is essentially a cut-off that defines the linkage area. The Corridor Design tool recommends creating slices of the lowest cost 0.1 to 10 percent of the total analysis area to define the actual linkage area (Fig. 4). This width requirement should be reviewed by the species experts. The Corridor Design tool also provides the ability to combine individual species linkages into a multi-species linkages. In many cases, individual species linkages may overlap, highlighting the importance of specific portions of the linkage area for more then one modeled species. A multispecies approach is also recommended for indicating where appropriately designed mitigation can benefit multiple species. GIS Mapping Step 5 – Biological review of
species linkage models A final review of the linkage models by the species experts is necessary to ensure that the linkages properly represent the species movement needs as accurately as possible and to determine whether any adjustments need to be made to the model inputs.
Figure 4:
Example of linkages between two defined core habitat patches, with
the recommended range of 0.1-10% of the analysis area displayed to
define linkage width. GIS Mapping Step 1 – Identify Analysis
Area(s) The Colorado Team had the benefit of a
statewide connectivity assessment to serve as the basis for the
Corridor Design analysis.
Linking
Colorado’s Landscapes, completed in 2005, was a
comprehensive effort to identify broad-scale movement corridors for GIS Mapping Step 2 – Compile List of Target
Species: The Partnership Team identified a diverse set of target species to capture the range of ecological and topographic conditions present in the state, with the intention of
Figure
5: High priority linkages
identified in creating a linkage design that would ensure their long-term viability. Target species met one or more of the following conditions: species identified as Tier 1 or Tier 2 species in the Colorado State Wildlife Action Plan (see box), species that are frequently involved in animal-vehicle collisions, and/or species of special management concern to CDOW (e.g., at-risk species, game species).
Notably, there are several species that were identified as target species at the outset of the project, but were later removed from the list of target species being modeled. For example, meadow jumping mouse is a riparian species restricted to the Front Range of Colorado. Given its habitat is naturally linear and restriction to the riparian zone, linkages for this species cannot be mapped in the same manner as for other species. Instead, it is appropriate to highlight all suitable habitat for this species as a ‘conflict zone’ where special consideration for avoidance and mitigation measures is needed to adequately protect the species’ ability to move through its habitat. Similarly, species with small-scale movements, such as herpetofauna and some small mammals might operate at too fine of a scale to have their movement patterns adequately captured using this modeling process. In these cases, suitable habitat may be a better determinant of where avoidance or mitigation measures are needed. Attempts were made to model gray wolf and mountain lion, however, it was determined that the parameters for these species were too general to discern linkages between habitat core areas. To adequately model linkages for these species, other factors, such as prey availability, may be better suited for representing these species use of the landscape. Following is a list of species that were determined to be inappropriate for inclusion in the linkage design process:
GIS Mapping Step 3 – Define Habitat
Parameters and Compile Data Layers We used the following data layers to define each factor in the habitat suitability models:
List of CDOW biologists Engaged in Model Parameterization:
We found working with the species experts to define parameters for each of the target species to be one of the most time-consuming steps in the process, require significant review of the literature as well as one-on-one collaboration. We found that a number of biologists, being unfamiliar with GIS modeling concepts, were hesitant to provide definitive weights for the factors and factor categories as required to construct the models – there can be significant natural variability in activity and habitat use within a species, and in many cases these details are not well understood. Working with the individual biologists was an educational and iterative process for the Project Team, but was well worth the effort to ensure that the resulting species models accurately reflect habitat use. Example: Parameters defined for Colorado’s Target Species GIS Mapping Step 4 – Adapt Corridor Design
Tool The corridors modeled in this case study were derived from a previous study conducted called Linking Colorado’s Landscapes which gathered together species experts from across the state and identify the highest priority linkages in the state. The results were sketches and lines of important wildlife linkages, but the study did not define the spatial extents of these linkage areas, thus the spatial mapping of these linkage areas was an important next step for integrating wildlife habitat and movement areas into the transportation planning process. Habitat Suitability Models (HSM) were created for bighorn sheep, black bear, Canada lynx, elk, mule deer, pronghorn, and swift fox using the process described by the Corridor Design methodology. Potential breeding patches and core habitat patches were then derived from the HSMs. In the case of bighorn sheep, existing populations are well known and do not occur in all areas of suitable habitat. In this case, data from the Colorado Division of Wildlife on these populations was used to define endpoints for the linkage modeling process. To best suit
Figure 6a:
Elk linkage at Dallas Divide in southwestern 
Figure 6b:
Lynx linkage crossing the same stretch of Highway 62. Note how the
low cost (low resistance) portions of the linkage are significantly
more restricted for lynx than they are for elk.
Figure 6c:
When unioned together, the details of the individual species
linkages may be lost. We therefore recommend reviewing the
individual species linkages
both separately and combined for a given location for a more
complete understanding of where mitigation efforts should be placed
for the greatest benefit to multiple species.
GIS Mapping Step 5 – Biological review of
species linkage models For each target species, we conducted individual meetings with the species experts in which we thoroughly discussed the modeling process, explained each of the inputs into the model, and reviewed the resulting linkage maps. The purpose of these meetings was to evaluate the models and determine if any adjustments were needed to better represent species’ use of the landscape. Each reviewer then responded to the following questions:
Questions to Ask · Does the State Wildlife Action Plan include data or maps for identifying conservation priorities and important habitat for species of conservation concern? · Be clear about the purpose of applying the Corridor Design analysis – what are you trying to connect? Why? Is this the appropriate tool for the job? · Does the suite of identified target species sufficiently represent the movement needs of native species in the analysis area?
Key to Success · Understand that many biologists are unfamiliar with GIS modeling, and may be hesitant to accept the modeling outcomes. Take the time to explain what the models represent and what they can and cannot do so that the species experts are better equipped to assist in defining habitat parameters. · Recognize that the one size may not fit all and that some species are not suited to a GIS modeling process. · Actively engage Division of Wildlife GIS staff in the modeling process. · Test modeling process through close collaboration with the species experts to fine tune the process and adjust parameters as needed. · Develop protocols to ensure that the linkage data is kept up to date. In general, such revisions are unlikely to be needed very frequently, as major changes and new insights into our understanding of a species habitat or habitat preferences are infrequent. Previous | Next | Table of Contents |
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