Basically, I have my IUCN species distribution layers. I initially created a heat map with overlapping polygons (Count overlapping polygons tool) but that just gives me the species richness. I thought to make the results more robust by assigning priority scores to each species and create a 'heatmap' where it counts overlapping layers based on the priority scores added together. Is there a way to do this?

This is the output from using the count overlap polygons tool:

enter image description here

I want something similar to this but based off the sum of this value field. So the higher the sum of priority scores as each species layer overlaps with one another, the higher the conservation priority of the area will be.

enter image description here

  • Hi there, thanks for your reply! I've edited my question. Hope it is clearer now.
    – NLS
    Jul 2, 2023 at 12:53

1 Answer 1


You can calculate the values you desire with a simple model or run them individually as there are so few steps. It uses the Union tool on the layer to create all combinations of polygons, then using a trick you extract out the centroids to create a unique identifier for the polygon location (which may be a stack of polygons) and then you dissolve on that.

Sample input, polygons labelled with a priority value:


The model:




Here are the individual tool settings:


  • Thanks so much for the simple workaround! My dissolve tool failed due to invalid topology but I did try to use pairwise dissolve instead and it worked.
    – NLS
    Aug 3, 2023 at 8:42

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