In our increasingly interconnected world, invasive species can be a huge issue. With proper data, you can map these species easily using ArcExplorer Java Edition for Education (AEJEE), ESRI's free, downloadable, dual platform (Win/Mac), lightweight GIS tool. This week's episode of "Fun With GIS" demonstrates the power of GIS for serious analysis.

I went to the US National Atlas, chose "Raw Data Download", chose the "Biology" series, and chose the "Invasive Species - Zebra Mussel Distribution" data set. This is a point file, so it was a quick process to download and unzip. I opened AEJEE and chose the "us48elev_hd.axl" project, which provides shaded relief and major rivers and lakes. I added the Zebra Mussel data and set the symbol as red dots with a black border, then hid the other legend items.

Wow! These little guys are making some serious trouble. But are they expanding their range? I looked in the Zebra Mussel attribute table and saw that the points all carried a "Year" field. Aha! A fundamental power of GIS is to highlight particular features with a query, which may emphasize a geographic pattern.

The data set ranged from 1988-2008. I built a statement of "Year > 2005" to highlight just the latest records. The map below shows the results.

GIS allows users to integrate disparate data sets, ask powerful analytical questions of an infinitely varied nature, and see the spatial pattern of the results. It's up to us to interpret the information and act on the data, but the better we understand the patterns and relationships, the better we can make critical decisions.

- Charlie Fitzpatrick, ESRI Education Manager