Because the earth's climate is CONSTANTLY in flux and what today is a desert was once a tropical forest.
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Answer:
It allowed an exodus of thousands of East Germans fleeing to West Germany via Hungary. The Peaceful Revolution, a series of protests by East Germans, led to the GDR's first free elections on 18 March 1990, and to the negotiations between the GDR and FRG that culminated in a Unification Treaty.
I'm 90% sure it's 2000 because urban areas now a days are overcrowed and cities have increased in size from the 1900's and the rest are pretty much both more for the 1900'spam than now but what I think it's more towards 2000's
