Looking for answers about forest regrowth mechanics

[fenrus]

It was hard to find a narrow search to find what I'm looking for, but basically I want to know some of the mechanics of forest regrowth.

Is there a chance a tile will grow a forest as long as it is touching a forest within it's 8 surrounding tiles?

Do forests regrow on Hills?

If I chop a Jungle that is adjacent to a Forest, will that chopped Jungle have a chance of growing out a Forest?

My projected GP city has a bunch of jungle and some Plain Forest. I'll obviously leave the Plain Forest. I could irrigate the chopped Grassland Jungle, but I could also hope it would grow a forest for my future National Park. Or maybe I can wait until I can make Forest Preserves before I try to purposely grow some forest. Is it worth the effort to try and purposely grow trees by the time you have Scientific Method?

Or I could also just leave the Jungle, but I don't like the unhealthiness.

 

[PieceOfMind]

Forests can regrow on hills.
Forests can only spread to tiles that are adjacent in one of the four cardinals (in other words, NOT on the diagonals) and that have no improvements on them.
Forests can spread onto roads but they are less likely (I think the chance is about half).
The maximum chance of a forest growing is a tile with 4 forests either side of it and no road.
Roads on the existing forests don't affect anything.

Not that anticipating forest growths is a very strong strategy IMO, but some have suggested cutting large amounts of forests in a checkerboard pattern as it would allow the highest chance of regrowth as you did it.

 

[Silu]

To add to the above, a chopped jungle can grow into a forest. Once you get NP though the jungle unhealthiness is obviously not an issue so you might as well preserve those

Also note that as forest growth is a chance each turn, forests grow three times as much on Marathon as on Normal. On Marathon at least it's indeed sometimes worth it to "cultivate" trees for the city where the NP will be, on Normal it's usually not worth the effort.

 

[Tristan_C]

In addition to what PieceOfMind said...

Preserved forests have double the chance of spreading into adjacent tiles.
A forest with a Lumber Mill does not spread.​

I try to do the checkerboard pattern in my games. A final verdict would require a lot more practical experience, and I'm a slow player... I just haven't played enough games to tell you whether it's worth sacrificing early chops to make this rather late-game bit for high production. I guess there are some general considerations we can spell out, though. Obviously, space between your cities is the prime place to leave forests alone since they don't give as many hammers for chopping, and can act as the "seed" for spreading forests into your marginal BFC squares. A forest that borders onto any random BFC tundra and plains squares is ideal. It may also be better to "fixate" your forest checkerboard in proximity to one city (namely, your candidate for NP), and just be entirely less merciful to forests elsewhere.

Finally, barring strategic concerns, avoid building roads adjacent to forests even if you improve the tile. This gives you the option of pillaging the improvement if your city's needs change, and letting that square try to grow a forest. I have used this strategy far more than once, on marathon. wish to god that we could pillage our own roads. Especially when you get new territory, the AI always covers the whole damn map in black spaghetti, which retards forest growth.

I side with TMIT on this, who wrote that unnecessary infrastructure is exactly that: unnecessary and a waste of time. If your workers have nothing to do, don't auto them and don't micro them, either, to do needless crap. Just ZZZ them in a city until you need them to do something important.

 

[fenrus]

Does anyone know the rules of regrowth or the probabilities?

hill vs. flat?
grass vs. plains vs. tundra? (i don't think forests grow on floods, desert, ice or on resource tiles)

 

[dirtyparrot]

I don't believe that the type of tiles matters in the probability of a forest growing there so long as it can grow there (e.g. forests won't spread to flood plains).

 

[Willem]

(i don't think forests grow on floods, desert, ice or on resource tiles)

There are some resource tiles where a Forest can grow into. Like Deer, Furs etc. And Jungle can grow over Rice and some other resources. Once the tile has been improved though, that can't happen.

 

[Tristan_C]

I too would like specific numbers for the regrowth chance.

Also, do rivers affect the chance of spreading, i.e., 1/2 chance from across the river?

Also, I don't remember ever seeing a forest regrow onto a wildlife resource square, but that's just heresay of course.

 

[Willem]

I too would like specific numbers for the regrowth chance.

The values are in the XML/Terrain/CIV4FeatureInfos.xml file. Look for the iGrowth line. Forests have a value of 8, Jungles 16. That represents a percentage chance, though I'm not sure if it's 8% or .8%. Either way it's quite low.

Also, do rivers affect the chance of spreading, i.e., 1/2 chance from across the river?

No, there's only the one value, with no modifiers.

Also, I don't remember ever seeing a forest regrow onto a wildlife resource square, but that's just heresay of course.

It's not hearsay, I've seen it happen plenty of times in my game. At least with Deer anyway. And I've also had Jungle grow over an Ivory resource plenty of times. Rice as well.

 

[Silu]

It's a chance per 10000, and that chance is multiplied by the global define FEATURE_GROWTH_MODIFIER (+ 1 and / 100 applied for it, default is 25) so it's 0.1% per surrounding forest, 0.2% for jungles.

 

[Tristan_C]

The values are in the XML/Terrain/CIV4FeatureInfos.xml file. Look for the iGrowth line. Forests have a value of 8, Jungles 16. That represents a percentage chance, though I'm not sure if it's 8% or .8%. Either way it's quite low.



No, there's only the one value, with no modifiers.



It's not hearsay, I've seen it happen plenty of times in my game. At least with Deer anyway. And I've also had Jungle grow over an Ivory resource plenty of times. Rice as well.

Thank you very much, I will take a look at the that sheet, then.

Also I was accusing MYSELF of hearsay, not you