but forests aren't really a production or food bonus...at least, that's the way I view forests. In light of that, that tells me that RR's will not do anything for forests.
No, as has been stated many times, railroads do not give any bonus to forests.
What railroads do is increase the output of any terrain
improvement by 50%, rounded up. As it happens, this always works out to a +1 bonus in the standard game. For example, let's say you have irrigated a floodplain wheat. The floodplain gives 3 food by itself, +2 for the wheat, for a total of five. Irrigation increases that by +1, to six. Now you add a railroad. If railroads increased the output of the whole tile by 50%, you would expect to get 9 food from the tile. But it doesn't. It adds 50% of the irrigation bonus, rounded up, or 1*0.5 = 0.5, which rounds to +1. Railroaded, irrigated floodplain wheat produces 7 food, the highest in the game.
The highest value terrain improvement bonus is a mine on a hill or mountain, which gives a +2 shields. But of course 50% of +2 is still just +1, so railroading a mined hill still gives you only one additional shield.
Unless you play modded games, you can just think of railroads as giving a +1 improvement bonus, and you'll come out the same.
But the shields from a forest are not coming from a terrain
improvement, but from the terrain itself. Therefore, there is no bonus applied from a railroad, as has been reiterated several times. Similarly, the floodplain wheat we mentioned above gives 5 food without irrigation. If you put a railroad on that non-irrigated tile, it still gives "only" 5 food.
