Very late replay and you've probably already sorted it.
For Syria, I found the Anabasis_setifera plant the most troublesome and jarring "pop up" - in Mods/terrain/Syria/surface details - I just rename it to "Anabasis_setifera_0.ref" so the game doesnt see it - I have to delete the newly created file for it every patch but thats no big deal.
In PG in the PG surface details folder I do the same with "small_bush" and "small_bush-group"
Caucuases has has large number of smaller shrubs hiding under the forest canopy - these are not a pop up problem but removing or renaming "Bush.ref" can ease the load a little without undult affecting the quality of the graphics - this can also ve permanently edited out in one of the lua. files but I forget which.
Hi. Its ok on my system. If you have and mods disable or remove them. Perhaps try deleting the FXO and Metashaders2 folders in Saved games and, if that doesnt work, run a repair.
Boosterdog's post in Syria and other map bush/clutter pop in was marked as the answer