Wow. That's actually a really cool concept.
So are the protagonists actually aiding in the demise of the planet by using materia?
By "life" do you just mean nature or human life also?
There was a scene with a shooting star
All life, I'll leave it to you to philosophize about what life is made out of, but lifestream is made up out of life, and life is made up out of lifestream, they're the same thing. Memories, fantasies, dreams, consciousness, personality, in other words, the soul. That is the lifestream.
The precise mechanics are never laid out but I always imagine it as patterns, just like patterns in a book combine to form words, then sentences, so too do the patterns in the lifestream define individuals. When you die, your experiences rejoin the lifesteam and become a part of the overall pattern as you slowly diffuse into it like a bucket of water thrown into the ocean.
From what I gather, normally, over time, all those accumulated experiences do allow for the lifestream to grow, I don't think there is a SET amount of it that is forever unchanging (evidenced by the fact that it's being used up). Materia does actually exist naturally out in the wild, it's just that the massive industrialized extraction of it that simply makes it too much for the planet to handle.
Aeris meantioned learning more about the Cetra and the Promised Land.
Was I supposed to find something as well?
I think you might be confusing Cosmo Canyon, the place where Nanaki comes from, with Gongaga, which is a town you could have gone to just before that, and shows you quite a crucial piece of the puzzle. Not sure if you can backtrack for those scenes.
