Using IUCN-Data, ArcMap 9.3 and R to Map Species Diversity

I'm overwhelmed by the ever-growing loads of good data that's made available via the web. For instance IUCN collects and hosts spatial species data which is free for download. I'm itching to play with all this data and in the end there may arise some valuable outcome:)

In the below example I made a map for amphibian species richness without much effort. I used a 5x5 km grid (provided by Statistik Austria) and amphibian species ranges and intersected this data to yield species numbers per grid-cell. For aggregation of the tables from the polygons, that were produced by intersection, I needed to switch from ArcMap to R because ESRI's "Summary Statistics" only cover MIN, MAX, MEAN, FIRST/LAST... and there is no easy way to apply custom functions. So I just accessed the dbf that I wanted to aggregate with R and did the calculations there.. Then reloaded the layer in ArcMap and was done..