Table 1.
Predictors and variable importance scores in seasonal distribution models of the Western Arctic Herd
| Included 2010 Predictors (units) | Source | Spring | Calving | Insect Relief | Late Summer | Fall | Winter |
|---|---|---|---|---|---|---|---|
| Active Layer Thickness*∆ (m) | www.snap.uaf.edu/tools/data-downloads | 31.0 | 15.1 | 16.6 | 15.6 | 31.4 | 18.4 |
| Aspect (°) | ned.usgs.gov | 27.6 | 13.5 | 11.3 | 15.2 | 24.6 | 10.6 |
| Coast Distance (m) | www.asgdc.state.ak.us | 43.3 | 23.6 | 18.3 | 24.0 | 42.9 | 34.8 |
| Elevation (m) | ned.usgs.gov | 30.6 | 13.2 | 14.3 | 15.7 | 32.3 | 16.1 |
| Freeze Date*∆ (Julian date) | www.snap.uaf.edu/tools/data-downloads | 9.7 | 4.2 | 3.1 | 5.3 | 17.9 | 7.3 |
| Thaw Date*∆ (Julian date) | www.snap.uaf.edu/tools/data-downloads | 17.2 | 5.5 | 5.1 | 4.1 | 12.3 | 8.5 |
| Fire History∆ (year) | agdc.usgs.gov/data/projects/fhm | 14.6 | 3.8 | 2.5 | 3.2 | 14.1 | 15.9 |
| Lake Distance (m) | nhd.usgs.gov | 31.5 | 15.3 | 11.6 | 17.6 | 29.4 | 15.5 |
| Growing Season Length*∆ (days) | www.snap.uaf.edu/tools/data-downloads | 32.8 | 9.6 | 6.2 | 10.0 | 51.2 | 16.0 |
| Ground Temperature*∆ (°C) | www.snap.uaf.edu/tools/data-downloads | 36.6 | 14.8 | 11.7 | 15.0 | 64.6 | 21.3 |
| NDVI Greenup Rate∆ (−0.2˗˗1.0) | nhd.usgs.gov | 25.6 | 13.7 | 11.7 | 16.1 | 24.8 | 10.7 |
| Max NDVI∆ (−0.2˗˗1.0) | alaska.portal.gina.alaska.edu/search | 22.2 | 5.4 | 7.9 | 17.9 | 27.5 | 15.6 |
| Potential Evapotranspiration*∆ (mm/yr) | arcticlcc.org/products/spatial-data | 69.0 | 100.0 | 100.0 | 28.1 | 100.0 | 35.5 |
| Permafrost Probability (%) | [91] | 18.9 | 10.6 | 10.2 | 16.0 | 32.9 | 18.1 |
| Winter Precipitation*∆ (mm) | www.snap.uaf.edu/tools/data-downloads | 100.0 | 13.0 | 8.0 | 57.6 | 47.1 | 25.3 |
| Summer Precipitation*∆ (mm) | www.snap.uaf.edu/tools/data-downloads | 26.7 | 12.7 | 14.2 | 21.4 | 34.0 | 26.9 |
| Spring Precipitation*∆ (mm) | www.snap.uaf.edu/tools/data-downloads | 31.5 | 25.4 | 6.7 | 15.8 | 27.8 | 19.1 |
| Fall Precipitation*∆ (mm) | www.snap.uaf.edu/tools/data-downloads | 35.7 | 12.5 | 35.5 | 20.1 | 44.4 | 21.1 |
| Stream Distance (m) | nhd.usgs.gov | 30.1 | 13.9 | 10.8 | 15.8 | 26.8 | 13.9 |
| Road Distance (m) | www.asgdc.state.ak.us | 60.9 | 31.1 | 26.5 | 27.9 | 44.3 | 39.1 |
| Max (Mar) Sea Ice Distance*∆ (m) | [92] | 53.4 | 18.7 | 12.9 | 17.1 | 41.8 | 30.9 |
| Min (Sep.) Sea Ice Distance*∆ (m) | [92] | 58.3 | 47.5 | 16.4 | 21.9 | 43.2 | 37.4 |
| Slope (⎕) | ned.usgs.gov | 28.4 | 13.3 | 12.2 | 17.9 | 34.8 | 13.0 |
| Winter Snow Day Fraction*∆ (%) | www.snap.uaf.edu/tools/data-downloads | 11.6 | 2.8 | 14.1 | 24.7 | 20.6 | 100.0 |
| Summer Snow Day Fraction*∆ (%) | www.snap.uaf.edu/tools/data-downloads | 18.1 | 10.0 | 6.1 | 9.3 | 14.8 | 10.0 |
| Spring Snow Day Fraction*∆ (%) | www.snap.uaf.edu/tools/data-downloads | 25.2 | 7.2 | 7.0 | 9.0 | 16.1 | 13.6 |
| Fall Snow Day Fraction*∆ (%) | www.snap.uaf.edu/tools/data-downloads | 26.6 | 7.0 | 6.9 | 100.0 | 23.7 | 19.9 |
| Snow-free Date*∆ (Julian date) | [62] | 64.2 | 10.4 | 9.3 | 11.7 | 27.7 | 25.8 |
| Winter Temperature*∆ (°C) | www.snap.uaf.edu/tools/data-downloads | 25.8 | 17.4 | 9.0 | 15.6 | 29.5 | 28.1 |
| Summer Temperature*∆ (°C) | www.snap.uaf.edu/tools/data-downloads | 28.3 | 15.4 | 7.6 | 10.2 | 28.5 | 12.0 |
| Spring Temperature*∆ (°C) | www.snap.uaf.edu/tools/data-downloads | 22.0 | 12.1 | 9.8 | 10.5 | 24.7 | 12.6 |
| Fall Temperature*∆ (°C) | www.snap.uaf.edu/tools/data-downloads | 65.4 | 20.8 | 9.3 | 13.7 | 26.6 | 21.4 |
| Distance to Trails (m) | www.asgdc.state.ak.us | 35.7 | 16.1 | 17.0 | 18.9 | 34.2 | 23.6 |
| Terrain Ruggedness 17 × 17 (0–1) | ned.usgs.gov | 28.2 | 20.6 | 18.7 | 21.4 | 28.8 | 33.7 |
| Terrain Ruggedness 3 × 3 (0–1) | ned.usgs.gov | 26.5 | 13.8 | 12.1 | 16.1 | 24.4 | 10.5 |
| Community Distance (m) | www.asgdc.state.ak.us | 43.4 | 14.9 | 11.9 | 15.1 | 43.6 | 13.6 |
| Wetland Distance (m) | https://www.fws.gov/wetlands/Data/Data-Download.html | 25.4 | 13.7 | 11.9 | 15.6 | 30.7 | 13.8 |
Predictors denoted with an * are decadal means, and ∆ indicates dynamic predictors that change annually. Active layer thickness is the depth of ground that thaws and freezes each year. Freeze and thaw dates refer to the mean annual date of first freeze (or thaw) during 2010–2020. Fire history denotes the year of the most recent fire in a given area. Growing season length is defined as the number of days between the date of first thaw and date of first freeze. Ground temperature refers to the modeled mean annual ground temperature. NDVI (Normalized Difference Vegetation Index) is an infrared-based measure of landscape greenness indicative of biomass; green-up rate and maximum NDVI are annual metrics calculated from NDVI. Potential evapotranspiration (PET) here is the amount of evaporation that would occur over a year if a sufficient water source were available. Seasonal climate variables are decadal averages of downscaled seasonal totals. Seasons are grouped as follows: Spring (Mar.-May), Summer (Jun.-Aug.), Fall (Sep.-Nov.), Winter (Dec.-Feb.). Permafrost probability describes the distribution of near-surface permafrost. Distance refers to the shortest Euclidean distance to the nearest feature. Snow day fraction is an average of the percentage of days with snow on the ground. Terrain ruggedness predictors were calculated from slope and elevation using 2 moving window scales of 3 and 17 m, respectively. Predictor importance values are out of 100.0 with the top predictor always receiving the maximum