Pollution

Pollution is the result of industrial waste in a colony. Each biome type can withstand certain maximum pollution level before degrading (see biomes for absorption levels).

Overview
Pollution builds up as a byproduct of Production, increasing by a percentage depending on the amount of production generated and Food slots are less effective. Once it reaches 100%, the planet's biome drops drastically, usually by one rank class: gaia to terran, terran to arid or swamp (depending on planet orbit), grassland to arid, tropical to swamp, inferno to volcanic, arid and cavernous to desert, ocean and swamp to tundra, desert and tundra to barren, and barren to toxic. (Radiated planets also downgrade to toxic, however they are immune to pollution.) Managing pollution can be done with the pollution clean-up project or by building dedicated structures.

If pollution does accumulate, the planet can be restored through terraforming. This is the only way short of destroying the planet with a Stellar converter or a supernova to revert an Uber planet to one that can be terraformed to Gaia or vice versa.