We do maintain those barren concrete parking lots to stay as clean as possible and, because of this, they stay hostile for life ! … but the minute we stop keeping them clean, vegetation takes over like on most barren rocks in nature. We do so because we, humans, like it like that.

Unfortunately we have also created disaster chemical zones after heavy industries have left some lands. And if we try to live there we get very sick.

i will not try to come up with a clear definition but for me something natural or artificial is not a yes or a no question, but rather a more or less question.