Regrowing Forest For Cities ??? Help Me Out

[Shadoz]

I play RoM 292 without a modmod ...

I am in future era and all my cities dont have any forest titles ...
Is there now a possibility to get forest to all cities ?? ... far away but in my cultural radius are some forest titles ... can i build an improvment like treefarm or preserved forest on it and it spreads the forest from time to time ??? ...

i play without random events so how to get forest to cities wich are all empty titles of forest ???

I hope someone can help me out please ...