Well its all due to Green house gasses produced through factories and automobiles, with the abundance of the world, driving, fly, and burning gas and oil on the whim we are playing a major role in this and unless a new technology that can surpass oil and natural gas we are slowly killing ourselves and the world.
A green card doesn't have anything to do with citizenship, but is important if you want to stay here for a long time without committing to a citizenship. If you are ready, take the citizenship test. If not then get a visa or green card and take a course to become a citizen.
The answer is Africa and Europe.
<span>Sand dunes move because of wind, so to prevent a sand dune from moving you need to either: stop the wind; or stop the sand dune from being able to move. For example, on beaches, sand is stopped from moving by using groynes, which physically stop the sand from being carried any further along the beach
(Copied from my comment, pasting it here because I know on mobile apps you can't see comments, so if anyone searches, etc.)</span>
