In essence: I'm playing around with a few ideas relating to a post apocalyptic United States, and one of the concepts I've come up with is a world of mostly dusty deserts and other regions mostly devoid of life, and, more importantly, are nearly impossible to live in - you can't grow food there and the conditions are not ideal for long-term settlement. However - not all is lost for humanity, as some large areas (say perhaps the largest would be about the size of Vermont, but far often smaller areas closer in size to Delaware or Rhode Island) grow green and lush, with an environment that is usable for permanent settlement.
My question is: How, realistically, can this occur, and what criteria, or features of a location, if any, would alter the transformation from into a wasteland devoid of life to a location lush with it?
Here's what I'm looking for:
- The occurrence that would would cause a situation like this to arise. By this, I mean what series of changes to the regions climate would have caused this situation. Factors such as temperature, that kind of thing.
- Why this situation is continuing, and the world wouldn't revert back to it's pre-disaster state. Here, I'm looking for reasons why the wastelands don't become able to support life again, or if they do become able, it happens so slowly that it barely matters.
- The criteria, or features, of a location that would cause it to develop into one of the "lush" areas. Again, details such as temperature, elevation, perhaps the amount of water in the area - those details would be really helpful.
- Any other features about your scenario that you think might be important would also be helpful - I'd like my world to be at least scientifically plausible, and I'd hate to leave out possible important details.
Speaking of important details:
I think there's a few details I owe you regarding to what I was thinking about.
- I'd prefer the disaster to be something that could occur naturally - I'm not averse to a human-created set of circumstances leading to the disaster, but I'd rather the disaster not be something that occurs directly due to technology - instead of nanites altering the climate through the change of weather patterns, the nanite foundries produce pollution that causes climate change.
- Along the same lines, I'd rather the disaster not directly be caused by humans, but by a natural series of circumstances that were perhaps helped along by humans - by this, I mean I don't want something that humans deliberately did, as that's not part of the ideas I want to explore with this concept.
- In terms of timeframe, I'm perfectly happy for the change to be something that gradually occurred over the course of centuries - I don't particularly mind how long it takes to happen, as long as it happens.
- I'm not too fussed over the exact details of the wasteland - as long as it's unable to support life, and is problematic to even travel in for a short time, I think anything should work.
For those of you who decide to answer, I'd like to thank you in advance for helping me figure out how this would work. If you see any problems with my question, feel free to ask me to clarify them, and I should be able to reply within a day or so.