Crucial Habitat Assessment Tool

Map showing aggregated assessment of habitat.
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ADF&G developed this aggregated map with the following habitat values:
  1. Terrestrial species of concern, comprised of Threatened and Endangered species;
  2. Other species identified in Alaska’s Comprehensive Wildlife Conservation Strategy;
  3. Aquatic species of concern based on the Anadromous Waters Catalog;
  4. Species Richness;
  5. An index of Freshwater Integrity based on NFHP
This map display is based on 10 square mile hexagons. Habitat designated as “crucial” on this map reflects an expanded acreage due to the scale. A datapoint from layers 1, 2, 3, and 5 within the hexagon results in added value; layer 4 requires 50% coverage.


Through an initiative of the Western Governors’ Wildlife Council (WGWC), the Alaska Department of Fish and Game (ADF&G) is creating a web-based tool that allows the public to view crucial wildlife habitat and corridors. This online GIS-mapping tool is designed to provide a coarse-scale view of crucial habitat to inform the pre-planning phase of energy and infrastructure development, among other land use planning objectives. This interactive application allows the user to compare their area of interest with crucial habitat as defined by the State; this is provided in a non-regulatory context.

In December 2013, the Western Governors’ CHAT was published on the internet with habitat information shown across the 16 western states that participated in its development. On this first west-wide version, Alaska displays an aggregated layer for Crucial Habitat based on four habitat values described within the map above. At this preliminary stage, Alaska also displays information for two distinct layers: Terrestrial Species of Concern and Aquatic Species of Concern, which will be updated upon the launch of the Alaska CHAT in 2014. Additional layers are attributed for Level (HUC) 6 Watershed Boundaries, Protected Areas by Land Ownership (PAD-US), and Protected Areas by GAP Status (PAD-US).

Next Steps

The Alaska CHAT is scheduled to be published in December 2014. ADF&G biologists and GIS analysts are coordinating their efforts to compile species data and conduct further analyses to specify crucial habitat. This first iteration of the Alaska CHAT is intended to serve as a resource depicting important habitats for the major game species across the state. Additionally, a suite of fish and wildlife habitat maps and other landscape level features will be served on this site. Updates to the tool will be made as more mapping products are developed to support common needs by the conservation and development communities. This “living” tool will also be updated when changes to crucial habitat are demonstrated through analysis of species location data, seasonal use patterns, and habitat.

Download WGA CHAT Update for Alaska (PDF 258 kB).


Mapping Application

Until the Alaska CHAT is ready for publication, ADF&G has prepared a suite of habitat maps, some of which are currently displayed on the Western Governors’ CHAT. Additional sample maps are posted here to provide a framework of what to expect when we do publish the tool.

Current Maps:

Terrestrial Species of Concern

Map showing areas of terrestrial species of concern.
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This layer includes mammals and birds that are federally listed as threatened, endangered, candidate, or proposed; Natural Heritage G1/G2 or T1/T2; and high profile species of current management concern.

Observation data (i.e., Element Occurrence (EO) and Alaska Gap Analysis Program (AKGAP) point observations) were filtered to remove records documented prior to 1975 as well as records that occurred outside of the known range of the species. All records with a locational accuracy of 10,000 meters or greater were removed. Exceptions to this rule were museum specimens (for mammals) and Avian Knowledge Network records (for birds), which were retained for select species that had few other observation records.

In order to account for locational accuracy, and to remain consistent with the EO polygon format, we buffered AKGAP point observations by 2,000 meters (~1 mile). Then, the confirmed observations (EO and AKGAP buffered observations) were intersected with the 10 mi2 hexagon layer. If any part of a hexagon intersected with a confirmed observation, the hexagon was attributed as containing the observation.

The AKGAP distribution models were also intersected with the 10 mi2 hexagon layer. After intersecting the confirmed observations and distribution models with the 10 mi2 hexagon layer, each hexagon was assigned to a priority category based on the conservation status of the species and types and quality of data within the hexagon area.

Six priority categories were created. Hexagons containing species with federal status and confirmed observations were ranked higher than hexagons containing only distribution models for species lacking federal status. When a hexagon contained observations, models, and/or species that fell within multiple priority categories, the highest priority category was assigned to that hexagon. The final prioritization considers whether a species is known or suspected to be present within a hexagon, but does not consider the number (total count) of species present (e.g., 1 threatened species compared to 3 threatened species) within a hexagon.

Aquatic Species of Concern

Map showing aquatic species of concern.
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The Aquatic Species of Concern layer includes waters important for Alaska's anadromous fish species. All records within the Anadromous Waters Catalog were joined with polylines representing sections of water bodies. These polylines were then intersected with the 10 mi2 hexagon map for Alaska. If any part of a hexagon contained a polyline it was attributed as containing a water body important for anadromous fishes.

Freshwater Integrity

Map showing freshwater integrity.
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The National Fish Habitat Action Plan (NFHAP) HUC 12 coverage for Habitat Condition Index (HCI) was intersected with the 10 mi2 hexagon map covering Alaska. The greatest NFHAP HCI score for each hexagon was used for setting the priority level. A head/tail breaks classification (Jiang, 2012) was used to determine 6 priority levels due to the heavy-tailed distribution of the NFHAP scores.

Species Richness

Map showing species richness.
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This layer represents the richness of native terrestrial wildlife species in Alaska. Richness was derived using distribution models from the AKGAP for breeding and year-round amphibian, bird, and mammal species. This assessment does not include plant, invertebrate, or fish species.

Due to the large geographic size and thus inherent differences in habitats and biodiversity across the state, richness values were normalized by ecoregion. The resulting richness values highlight areas of high and low diversity within each ecoregion of the state, taking into consideration the relative minimum and maximum richness values for that ecoregion.

The resulting product is a gradient of relative richness values that are comparable between ecoregions on a common scale of 0 to 1. The richness layer incorporates distribution models for 318 regularly occurring amphibian, bird, and mammal species that breed or are permanent residents in Alaska. AKGAP attempted to model all regularly occurring terrestrial wildlife species in Alaska, however, there were several species for which models were not considered representative of the species distribution, thus, those species models were not included in the richness calculation. These included Slaty-backed Gull, Common Murre, Thick-billed Murre, Cassin’s Auklet, Parakeet Auklet, Crested Auklet, Rhinoceros Auklet, Snowy Owl, Sky Lark, Gray-headed Chickadee, Song Sparrow, Gray-crowned Rosy-Finch, Arctic fox, and bushy-tailed woodrat.

The 318 individual distribution models were intersected with the 10 mi2 hexagon layer. At least 50% of the hexagon had to intersect with AKGAP modeled output for the hexagon to be attributed with the model. The total number of models that intersected with each hexagon was summed, resulting in a total richness count for each hexagon. In order to display areas of high and low biodiversity in each of the ecoregions, richness values were normalized to a common scale of 0 – 1.

Crucial Habitat Rank

Map showing crucial habitat rank.
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This is an aggregated layer reflecting five habitat values: 1) terrestrial species of concern, comprised of threatened and endangered species, G1/G2, T1/T2, and others; 2) other species identified in Alaska’s Comprehensive Wildlife Conservation Strategy; 3) aquatic species of concern based on the ADF&G Anadromous Waters Catalog; 4) species richness; and 5) an index of freshwater integrity based on the 2010 National Fish Habitat Partnership’s (NFHP) assessment of human effects on fish habitat. This rolled-up habitat map will be updated as ADF&G adds more layers and data to its assessment of crucial habitat across the landscape. The next iteration is expected to accompany the December 2014 publication of the Alaska CHAT.

Crucial Habitat Data Input Layers

ADF&G has been a participant in the Western Governors’ CHAT project since 2011. Through many meetings of state “CHAT” leads, decisions were made on which data sets would be useful to the development and conservation applications of the CHAT. The final version of these data sets for the Western Governors’ CHAT is described in the WGWC White Paper (revised July 2013) (PDF 658 kB). While all of these data sets are valuable, some are not applicable to Alaska because of scale, integrity of the landscape, and the limited capacity to expand infrastructure based on this state’s landscape features. Categories described below are those anticipated for inclusion in the Alaska CHAT. Distinct data sets within these categories will eventually be displayed separately on the Alaska CHAT upon its publication.

Species of Concern

Species of state and/or national conservation importance, including those vulnerable to extinction or those undergoing regional decline or other species requiring special management attention. Most states defined their Species of Concern list using State Wildlife Action Plan "Species of Greatest Conservation Need" and NatureServe conservation status rankings, and other criteria in some cases. Alaska’s version of this layer is described above where this map sample is shown.

Freshwater Integrity

Measure of freshwater habitat condition, typically including landscape variables and land use variables that are known to impact aquatic ecological systems.

Riparian and Wetland Habitat Distribution

Areas that represent unique and/or sensitive environments and function to support animal and plant diversity with respect to wildlife objectives and connectivity.

Species of Economic and/or Recreational Importance

These may include game or sportfish species especially if habitat needs are not already covered by mapping "Species of Concern."

Hexagonal Display

The CHAT will be displayed in a hexagon format. A “Hex Map” or hexagon covered map is one method of covering a landscape of polygons by creating a “grid.” Squares (pixels), triangles, rectangles, hexagons, octagons, etc. are all options for creating a grid. However, hexagons provide a computationally “easy” way of dealing with distance to center issues (all sides of a hexagon are closer to the true center of a cell than a square). They also require less information than an octagon (6 vs 8 vectors). So they provide a suitable compromise for many cases of coverage analysis.

While Alaska is currently displayed using a 10-square mile hexagon grid, future mapping products used in the Alaska CHAT will likely be displayed at a finer resolution of either hexagons or polygons.


Map Layers

Map layers are currently being prioritized by project timelines in relation to other agencies and infrastructure development interests. For example, the Alaska Department of Natural Resources is developing the North Slope Area Plan through the Division of Oil and Gas. This effort will benefit from updated crucial habitat maps parallel to those in development for the Alaska CHAT to manage state land surface uses on the North Slope. Related is the Alaska Department of Transportation and Public Facilities initiative called Roads to Resources. This program serves the design and construction projects that support development of natural resources where access currently does not exist.

Similarly, the U.S. Bureau of Land Management is conducting Rapid Ecoregional Assessments across the state, including the North Slope that will also use these same mapping products to develop habitat conservation strategies and to inform land use planning by synthesizing interagency values with biological data. Providing these products to the intergovernmental forum of the North Slope Science Initiative addresses the research, inventory, and monitoring needs as they relate to development activities on the North Slope.

With numerous efforts focused on the North Slope, and other development interests occurring statewide, crucial habitat delineation is key to conservation of Alaska’s fish and wildlife resources while guiding responsible development.

Along with the Crucial Habitat data input layers described in the Mapping Application tab, ADF&G is working to produce species specific maps to delineate crucial habitat representing hunting and subsistence resources. An example of this would be crucial caribou habitat by herd. While there are 32 herds across the state, we have selected a subset of these herds to include in the Alaska CHAT. Within each herd, there are usually specific habitats for calving, insect relief, wintering and migration corridors. In 2014, we expect to complete most of these analyses and include 2013 telemetry data where applicable.

To complete the caribou crucial habitat map, nine primary herds will be addressed: Western Alaska, Central Alaska, Teshekpuk, Mulchatna, Nelchina, Southern Alaska Peninsula, Northern Alaska Peninsula, Fortymile, and Porcupine. Considering the frequent and prominent interest in caribou, the Alaska CHAT will have a stand-alone caribou layer for viewing the individual herd information. Beyond caribou, the Alaska CHAT will serve crucial habitat information on the following species: Dall sheep, mountain goat, wolf, black bear, wolverine, grizzly bear, moose, deer, and muskox along with anadromous fish. Other species may be added over time.


Data Availability

The Alaska CHAT intends to specify priority wildlife habitat and corridors online for public use so that conservation of these areas can be integrated into the pre-planning phase of energy and infrastructure development, or other land use plans. Recognition of crucial habitat early in the process allows developers to design geographic and temporal modifications into their projects’ timelines and management.

Projecting crucial wildlife habitat and corridors on the web also intends to support commonly asked questions about species ranges, locations and habitat use. Oftentimes, Department biologists are called upon to create maps and answer questions that a variety of interested parties are seeking. By posting these mapping and data products online for viewing and download, ADF&G information can be more readily accessed and used across the conservation and development communities.

While selected summarized data sets will be available for download on this website application, other data sets will require users to adhere to a data use agreement through a separate database, to be announced at a later date. Metadata will be attached to the data sets to explain the context of the data and appropriate use in further analysis.

Alaska Statute 16.05.815 “Confidential Nature of Certain Reports and Records” requires ADF&G to keep confidential specific location data of fish and wildlife species. Substantial research is done by Department biologists to track and understand fish and wildlife behavior. Much of this research is published in scientific journals and management reports and is used in the management of these species. While we cannot release the specific location information for these species, we can share summarized data and mapping products to enhance the value of this work in statewide and global applications.