Two-Species Suitability Map

Author

Rachel F Kruger

Create a map showing suitable habitat for two species

If you want to get an idea of which geographic regions are generally suitable for one species compared with another, you can convert the continuous suitability results from the MaxEnt model to a binary “suitable” or “unsuitable”, and map them together to show regions that are suitable for Species 1, Species 2, neither, or both.

  1. Convert continuous suitability raster to binary suitable/unsuitable
  2. Combine binary raster layers

1. Convert Continuous Suitability Raster to Binary Suitable/Unsuitable

1.1 Add Layers

  • Open QGIS and select from the top toolbar Layer > Add Layer > Add Raster Layer…

  • Under Source… Choose where your MaxEnt output files are located, and select “yourspecies_avg.asc”.

  • Do this again for your second species

1.2 Convert rasters to binary 1,0

  • Open “maxentResults.csv” in your MaxEnt output folder.

    • Search: “Equal” and find the column titled Equal training sensitivity and specificity X threshold.

      • X will be whatever output format you chose for MaxEnt. This could be raw, cumulative, logistic, or cloglog.

    • Scroll to last row: this is where the average values are. Take note of that number.

    • Repeat for the second species

  • In QGIS, choose Raster > Raster Calculator…

    • Select the … under Output layer, and choose the file name and location you would like to write the raster. We’ll call it “species1_bin”

    • In the calculator box, type:
      (“species1_avg@1” >= 0.3165) * 1

      • This will make any value 0.3165 or above a 1, and any value below it a 0.

    • Do the same for the second speciess.

2. Combine binary raster layers

  • In QGIS, choose Raster > Raster Calculator…

    • Select the … under Output layer, and choose the file name and location you would like to write the raster.

    • In the calculator box, type:
      (“species1_bin@1” = 0) * (“species2_bin@1” = 0) * 0 +
      (“species1_bin@1” = 1) * (“species2_bin@1” = 0) * 1 +
      (“species1_bin@1” = 0) * (“species2_bin@1” = 1) * 2 +
      (“species1_bin@1” = 1) * (“species2_bin@1” = 1) * 3 +

  • Right-click the new layer with the 4 different values (0, 1, 2, 3)

    • Select Properties… > Symbology

    • Click Render Type at the top, and select Paletted/Unique values

    • Click the green + symbol near the bottom until you have all the values

    • Relabel the “Labels” to say what they should

    • Click on the color squares to change the colors of each value