The game manual says that if you case a special resources tile, the special resource will be converted to a form appropriate for the new terrain type.
This is not correct.
Depending on the version of FreeCiv I was playing, one of two reactions would occur instead:
1) The special resource would remain, giving its original bonus to the new terrain type. (This was awesome. Oil, Buffalo and Iron on Hills, or Spices, Oasis, or Gems on Grassland were always spectacular.)
2) The special resource would be destroyed. This is what most recent versions have done, and what 2.1.9 is doing currently on my machine. (Win32 GTK2). This is the worst possible scenario, it sucks, and I hate it.
Does anyone know if this was changed on purpose, or if there's some game setting or compile option which controls this?
And if it's the latter, is there any way of making it a server-controllable option?
I dunno since I'm new, but I did find that when the terrain was reverted to it's original type, the special resource came back. Hope that helps.