When playing with Kastorio 2 and other mods it's possible to use the air filters to clean up pollution. I noticed that even after the air is 100% clean there's no way to recover from the damage. The ground stays black, trees aren't growing, the flood water doesn't dry up.

I'd like to see some sort of recovery - even if it's limited. Just having good soil again would make me feel glad I spent the time to clean up the environment.

I think this "recovery" feature already exists actually, but in my testing it seemed either not to be working or incredibly slow.

Yes, this is a longer process, just like in life. In order for the soil to recover, trees must grow on it. Each tree has its own life cycle, after which it dries up and rots. When a tree decays, the soil is restored.

I'm not sure why, but in my testing all the trees were completely gone. That must be why the soil didn't recover.

For the "Winter is Coming" and "Middle Earth" presets, trees do not grow as long as the day is shorter than the night. The duration of the day and night can be viewed by clicking "=" .

I was using the Middle Earth preset, I think I was around day 30. Would that be in the winter? If so that explains it.

Did you optimize this mod for UPS and multiplayer? I had some lag but that's to be expected as I had the options as aggressive as I could make them. During my research I found a somewhat similar mod called Noxys_Trees that claims to be performant, but I haven't tested it yet: https://mods.factorio.com/mod/Noxys_Trees