The first self-induced extinction was caused by bacterial oxygen waste. Since that era, the Earth has been completely overtaken by hideous oxy-philes, and they show no sign of leaving. But my fellow sub-cultures, we can take back our planet!
Though in general multi-cellular organisms are untrustworthy and greedy, we have finally found a kindred spirit. Homo Sapiens have begun diluting the harmful atmospheric contaminants and replacing them with methane and other nurturing, heat-retaining gases. They also process the solid carbonaceous waste that has built up over the stone and displaced the sea in so many areas. From it they extract vital heavy metals and other nutrients. They frequently store these in convenient repositories located across the planet, or disperse them in fluid corridors which finally return them to the ocean where they belong.
Yes, humans are our allies. Every day, they help us exterminate more of the unnatural biota that have taken hold, and soon things will be back to normal. They seem amenable to negotiation in the later stages of their lifecycle. Adults often nest under a protective layer of soil away from the poisonous Oxygen and at last emerge as proper cellular colonies. If we can help speed them through their adolescence, we may yet save the sea and restore our homeland to its natural state!