How do forest preserve work?

[Krazula]

I have a few questions about how forest preserves work.

1. Must the preserve be worked in order to get the higher chance to spread?

2. Will forests spread onto tiles with a road/railroad?

3. By how much does the chance of the forest spreading increase?

4. If one unimproved tile is surrounded by two or more forest preserve does that tile have a higher chance to become forested than a tile with only one forest preserve nearby?

5. Do the preserves have an effect on global warming?

Thankyou in advance for your help.

 

[UncleJJ]

I have a few questions about how forest preserves work.

1. Must the preserve be worked in order to get the higher chance to spread?

2. Will forests spread onto tiles with a road/railroad?

3. By how much does the chance of the forest spreading increase?

4. If one unimproved tile is surrounded by two or more forest preserve does that tile have a higher chance to become forested than a tile with only one forest preserve nearby?

5. Do the preserves have an effect on global warming?

Thankyou in advance for your help.

1. No
2.Yes, but the chance of spreading is halved by the road
3. It is affected by the number of forests and forest preserves that border sides of the tile that you want a forest to spread on to. As I best remember a forest preserve adds 4 times as much as a forest.
4. Yes, its chance each turn is double or more.
5 Not sure.

 

[Dresden]

#3: A preserved forest has 8 times the chance of spreading as an upreserved one (Growth parameter of 64 vs 8 in the XMLs)

An addendum to #4: Keep in mind that forests (preserved or not) can only spread in the cardinal directions: N, S, E, W; they don't spread diagonally. So an unimproved tile with forests directly N and E has twice the chance of getting a forest as one with only a N forest neighbor, but an unimproved tile with forests only NE, NW, SE, and SW has zero chance of getting a forest.

To answer #5: No. Forest Preserves have no direct effect on global warming; it is the forest itself which matters, not whether the forest has been preserved.

 

[Levgre]

so what is the % chance if you have 8 growth parameter?

 

[Levgre]

ah, found it...

[iGrowth * 1.25] * (# Adjacent Forests) out of 10000 Chance.

so 10 out of 10,000 or .1% chance... one every 1000 turns.

Max rate in ancient period, 4 forests on all four sides (diagonals don't count) equals

32 time 1.25 times 4 /10,000 = 300, = 1.6%.... one every 62.5 turns on average.

With 4 forest preserves, it is

64(4) times 1.25 times 4/10,000 = 12.8%.

So having adjacent forests is quite a big deal, 2 forests and 2 forest preserves(7.2%) would work just as well as 3 forest preserves(7.2%)

1 forest preserve equals .8% (+.8% for the 1st)
2 forest preserves equals 3.2% (+2.4% for the 2nd)
3 forest preserves equals 7.2% (+4.0% for the 3rd)
4 forest preserves equals 12.8% (+5.6% for the 4th)


1 forest equals .1% (+.1% for the first)
2 forests equal .4% (+.3% for the 2nd)
3 forests equal .9% (+.5% for the 3rd)
4 forests equal 1.6% (+.7% for the 4th)


As seen, the biggest jump proportionally comes from the first to the second, where it increases the rate by +300%. For the 3rd it increases by +125%. So it would be smart to make pains to at least have 2 forests around a tile, although the 3rd and 4th are very much progressively better also.