where does all this debris come from?

I would think the majority is human garbage from the silly space program. While our Oceans are dying we piss away our futures through funding cronies of past administrations----------- One good possibility is that the garbage may shade us from the sun and cool the planet-----sort of a garbage sunscreen?

lol... now that's a bit of wishful thinking. =P

Here's an idea: send up a magnet that will orbit around the earth and collect all of the debris! Pro: you collect a lot of harmful debris. Con: you end up with this huge blog of garbage, flying around the earth at thousands of miles per hour, with consequences more catastrophic than any one of the pieces of debris :/