Well, it's been about a week without a response so I'm going to assume I won't get one. In the meantime, I've found a thread that indicates that no such mod existed as of 2004. Indications are that the piece of code that tracks this part of the game is either impossible to tap into or not worth the effort. I'm also guessing that not enough people actually conduct intensive forestry operations for any of this to matter. My conclusion is that such a mod will probably never exist.
For those poor souls that wander in here looking for answers, I've found a thread that offers an alternative method of tracking forestry without a drawing program(pages 2 and 3):
Forestry Operations in Civ3
This method is easier on memory(which is the primary reason I was seeking a mod in the first place), but unfortunately my style of play involves a lot of abandoning and relocating cities for optimal tile usage and the information would be lost every time I abandoned a city. I guess I'll continue to trudge along praying that the game won't crash when I have the drawing program open.
Happy Civing everyone.
BTW, for anyone it might help, MGI Photosuite is easier to use than MSPaint IMO. It uses less memory and loads and updates faster.
edit: Hooray! All hope is not lost.
CivAssist II contains a feature known as "Shield Forest" in its World Map page that does exactly what I've been asking for (if you have the memory to handle it). I, however, do not have the memory to handle it and will continue to seek an in game version of this feature.