Are you insane?! Well... being Skull I suppose you are.
I'll try to put it simply. There are more types of "air" and minerals in space and the universe than humans could ever hope to consume before the universe collapses once again... which won't be for a few trillion years by my watch. Anyway, humans need Oxygen, but the air we breath is comprised mostly of Nitrogen and many other elements besides. Food is made up of different elements, that, like all things, are combined in different ways and in the proper amounts to provide sustainence for whatever organism feeds on them, so that whatever life exists can feed itself, and other organisms, excrete, reproduce, die, etc. as per natural function to keep the myriad webs of nature going along. Long story short, space has all of the resources we need and more, they just aren't in the correct form. Conversion isn't easy, but we're already capable of self-sufficient existence in hostile non-Terran environments for months and even years. All that's lacking is the money, believe it or not.
There is absolutely NOTHING practical or "environmentally friendly" about humans remaining on Earth. Unless we start so succumb to disease more easily, find permanently efficient ways to use resources, evenly distribute the world population and food supply, depopulate steadily to a self-sustainable level... humans will just eat and shit themselves out of existence. Even continuing as we are now, we'll have serious problems before the century is out, but if we continued this way we won't last the mellinium. That won't happen, though, because when a problem comes along that must be dealt with or face extinction in the near future, humans tend to fix it... but just a little. Not enough to actually fix it permanently because that would "take up too many resources and cost too much money to ensure the existence of future generations", and so mankind hobbles along through the centuries. How long will it last, I wonder. I hope not long... I'm pretty disgusted by it, even if I have to go too.
Zaijian,
Tiger
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