Can Science Prove the Sky is Falling?

I'm sure that science can prove, if the oxygen producing resources that are on the ground are lessened, the "sky" or atmosphere would fall upon us.  Is oxygen holding it up?  With that in mind, the trees don't grow as big or numerous as they used to, the ocean has a garbage pit the size of texas in it, and the amount of toxic fumes from machinery, autos, and living is probably more than the trees are breathing.  Is "the sky is falling" concept really all childhood stories or should people take a very serious look at what they're doing to this planet and do everything they can to quickly change it?