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Table 1 The predictor variables used by the Random Forests algorithm to create a global prediction map for avian influenza virus in wild birds.

From: A global model of avian influenza prediction in wild birds: the importance of northern regions

Predictor variable Details VIS Project source
Annual precipitation (mm) In mm; 30 arc-seconds, 1 km spatial resolution 100.0 WorldClim[29]
Mean temperature, June (°C) In °C; 30 arc-seconds, 1 km spatial resolution 85.2 WorldClim
Mean temperature, April (°C) In °C; 30 arc-seconds, 1 km spatial resolution 76.1 WorldClim
Precipitation of driest quarter (mm) In mm; 30 arc-seconds, 1 km spatial resolution 68.4 WorldClim
Mean temperature, November (°C) In °C; 30 arc-seconds, 1 km spatial resolution 64.9 WorldClim
Precipitation seasonality In mm; 30 arc-seconds, 1 km spatial resolution 63.1 WorldClim
Mean temperature of driest quarter (°C) In °C; 30 arc-seconds, 1 km spatial resolution 62.5 WorldClim
Annual mean temperature (°C) In °C; 30 arc-seconds, 1 km spatial resolution 54.8 WorldClim
Mean temperature, February (°C) In °C; 30 arc-seconds, 1 km spatial resolution 49.7 WorldClim
Mean temperature, January (°C) In °C; 30 arc-seconds, 1 km spatial resolution 45.7 WorldClim
Temperature seasonality Standard deviation × 100 45.0 WorldClim
Precipitation of wettest quarter (mm) In mm; 30 arc-seconds, 1 km spatial resolution 42.9 WorldClim
Mean temperature, December (°C) In °C; 30 arc-seconds, 1 km spatial resolution 38.6 WorldClim
Maximum temperature of warmest month (°C) In °C; 30 arc-seconds, 1 km spatial resolution 38.0 WorldClim
Precipitation of driest month (mm) In mm; 30 arc-seconds, 1 km spatial resolution 37.5 WorldClim
Mean temperature, October (°C) In °C; 30 arc-seconds, 1 km spatial resolution 36.1 WorldClim
Mean temperature, September (°C) In °C; 30 arc-seconds, 1 km spatial resolution 32.6 WorldClim
Precipitation of coldest quarter (mm) In mm; 30 arc-seconds, 1 km spatial resolution 32.3 WorldClim
Population density (persons/km2) Population density for 2010, 2.5’ resolution, persons/km2 29.3 Gridded Popn of the World, v.3[30]
Mean temperature of coldest quarter (°C) In °C; 30 arc-seconds, 1 km spatial resolution 28.4 WorldClim
Mean temperature, July (°C) In °C; 30 arc-seconds, 1 km spatial resolution 28.3 WorldClim
Isothermality (°C) (Mean Diurnal Range/Temperature Annual Range); In °C; 30 arc-seconds, 1 km spatial resolution 26.6 WorldClim
Mean temperature of wettest quarter (°C) In °C; 30 arc-seconds, 1 km spatial resolution 25.2 WorldClim
Mean diurnal range (°C) In °C, (mean of monthly temperature(max – min)) 24.3 WorldClim
Mean temperature, August (°C) In °C; 30 arc-seconds, 1 km spatial resolution 22.7 WorldClim
Mean temperature, March (°C) In °C; 30 arc-seconds, 1 km spatial resolution 21.0 WorldClim
Temperature annual range (°C) In °C; 30 arc-seconds, 1 km spatial resolution 18.4 WorldClim
Elevation (m) In m; 30 arc-seconds, 1 km spatial resolution 18.3 WorldClim
Predicted pig density (per km2) Animal density/km2; 3 min of arc 18.0 Gridded livestock of the world[31]
Mean temperature of warmest quarter (°C) In °C; 30 arc-seconds, 1 km spatial resolution 17.0 WorldClim
Precipitation of wettest month (mm) In mm; 30 arc-seconds, 1 km spatial resolution 15.0 WorldClim
Distance from coast (m) Calculated from coastline 12.6 Esri
Precipitation of warmest quarter (mm) In mm; 30 arc-seconds, 1 km spatial resolution 12.1 WorldClim
Minimum temperature of coldest month (°C) In °C; 30 arc-seconds, 1 km spatial resolution 11.2 WorldClim
Human footprint index Percentage of relative human influence (0–100) 10.4 Last of the Wild[32]
Distance from rivers, lakes, or wetlands Calculated from combined large and small lake polygons, nd lakes and wetlands grid 9.7 Global Lakes and Wetlands Database[33]
Slope Calculated from elevation 9.0 Esri
Human influence index Summative index of human disturbance (0–72) 8.8 Last of the Wild[32]
Predicted poultry density (per km2) Animal density/km2; 3 min of arc 7.9 Gridded livestock of the world[31]
Aspect positive degrees from 0 to 359.9, measured clockwise from north; calculated from slope 6.7 Esri
Mean temperature, May (°C) In °C; 30 arc-seconds, 1 km spatial resolution 5.4 WorldClim
  1. Variables are listed in order of their Variable Importance Score (VIS) or relative contribution to model accuracy as calculated by Random Forests.