I think the problem is that the space junk from us tends to be in a stable orbit, because we specifically positioned it to be in a stable orbit. And it would te

I think the problem is that the space junk from us tends to be in a stable orbit, because we specifically positioned it to be in a stable orbit. And it would tend to inhabit the same elevation as we like our satellites. Also, I suspect that most natural junk would not still be in orbit, as it would likely have already fell back to Earth, or left orbit. This isn't to say that all of the junk is ours, but it makes sense that a significant amount is.