the Description should just state. Spawners & Fish are now affected with poison Gas. I wonder if there's a setting to make fish Die in heavy pollution.
Spawner sizes grow with amount of pollution. like 10M? of pollution gets removed from the area and increases the number of spawners.
so if your pollution heavy you'd be surrounded with spawners by the time you explore like Nausicaä of the Valley of the Wind. Natures Guardian. i guess that's another mod
