Finding areas of overlap using ArcGIS Desktop [duplicate]

Question

I am going to have about 300 shapefiles representing the range of different species in the wild. What I want to be able to do is find areas where the most species occur to highlight areas where many of these species exist.

Is there a simple way to do that in ArcGIS Desktop 9?

Answer 1

You can use a method called "spaghetti and meatballs", described in an ESRI blog. There is a tool (for ArcGIS 10) to count overlapping polygons that you can download too. The general workflow is the following:

1. Merge polygons
2. Identity (Analysis)
3. Calculate centroids of overlapping areas
4. Spatial Join
5. Manipulate attributes for display purposes

As you can see, the results could be applied to species biodiversity mapping.