Burning the amazon down is something to worry about. Not afforesting widely and extracting timber from the amazon ecologically so it sequesters carbon and supplies materials replacing demand for carbon intense alternatives - is tragedy.

The advice that amazons contribution is "zero", hedged under this safety-net word "effectively" is false to the understanding of geophysics and natural history. I hope the professor will clarify his language after consideration.

I'm not arguing that it's not something to worry about. It certainly is something to be worrying about. But so are the tropical forests of Southeast Asia, which are arguably even more threatened.

But we should be worried about it because of the impact on global biodiversity. Not because we'll be running out of oxygen. Having ~20% oxygen in the atmosphere reflects a long-term equilibrium of biologic and non-biologic processes.

If advocates focus on the oxygen issue, adversaries can easily point to negligible changes, and argue that there's nothing to worry about.

And, as I said, to the extent that oxygen is an issue, we ought to worry even more about the oceans. They are by far the major oxygen source, and arguably more vulnerable to catastrophic collapse.