Remove all improvements from a map?

I was trying to get the virginia map from the Civil War scenario, and while I could easily remove all resources and cities, I couldn't seem to remove the manufactories, farms, roads, and other improvements from the map. Is this possible other than through painstakingly removing them one by one?

With WorldBuilder, there is no easy way. However, you can start CivV, setup a game using the map, and then before settling use FireTuner to remove all the improvements and resave the map.

The one line of Lua you would need to execute from the WorldView context of the Lua Console tab would be

Thanks!