Go after polyamory all you want -- if there is data about problems that are statistically likely to show up, I'd like to know about that, so that I can try minimizing the odds that we will experience them -- and we do experience some of the standard poly jealousy problems -- but if you are going to shoot a sacred cow, bring a high powered rifle, not a squirt gun.
This argument is vague and anecdotal. Being polyamorous, I automatically feel defensive when you, without putting out evidence, say that my lifestyle, my wife's lifestyle, and the life style of my other partners and metamours are all dangerous, bad, and we are making bad choices despite having tried our best to get things right.
Just as a first note, the atmosphere is about 20% oxygen, the fraction of that which gets turned over by plants in any given year is by comparison tiny, tiny, tiny, tiny. For reference, CO2, which all of that oxygen released by the Amazon is made from, is .04% of the atmosphere. You could kill every plant on earth, and we'd probably have enough oxygen for all of the animals to survive for longer than mankind has existed -- though you would get carbon dioxide poisoning at a much earlier point. But if the only CO2 was coming from respiration, it would still probably take tens of thousands of years before the concentration was dangerous.
The earth running out of oxygen is literally not something that anyone should worry about. This has a relationship to why a lot of people don't treat climate change as a serious existential threat. Perhaps there is some reason to think that it is that I haven't heard -- but most of the claims that it is super dangerous that I hear are like 'if the Amazon burns down, we'll all run out of oxygen and suffocate' -- and that simply won't happen.