Excess oxygen is actually harmful to humans, but all the climate warnings are about losing oxygen, not nitrogen edit: but when we look for habitable planets, our focus is ‘oxygen rich atmosphere’, not ‘nitrogen rich’, and in medical settings, we’re always concerned about low oxygen, not nitrogen.
Deep sea divers also use a nitrogen mix (nitrox) to stay alive and help prevent the bends, so nitrogen seems pretty important.
It seems weird that our main focus is oxygen when our main air intake is nitrogen. What am I missing?
edit: my climate example was poor and I think misleading. Added a better example instead.
Calling it “inert” is misleading. It’s involved in all kinds of chemical reactions that are essential for life (and lots of non-biological reactions, too). It’s only inert in the sense that most living things can’t use it directly from the air and rely on nitrogen-fixing plants and bacteria to make it into molecules we can use.