From earliest times man has had a tendency to wander. It seems that migration is a normal form of human activity. The migrations of people have changed world history. Man moves from one place to another for various reasons. His motivation to migrate may stem from the over- population of his homeland, an enemy invasion, food shortage, persecution, tribal unrest, political suppression, the need to search for water and grasslands or new hunting fields, or to satisfy a curious adventurous nature. Perhaps survival was at stake. Then, of course, there was always the quest to improve his living standard by seeking new opportunities in a new land.
A direct and immediate reason for man to vacate an area was the sudden advent of natural catastrophes, such as an earthquake, fire, flood, drought, or volcanic eruption. When groundwater dried up, fields and pastures turned into dust bowls and desert; man had no alternative but to flee his native habitat. Often his life changed, sometimes radically, as the climate of his region changed, bringing hardship and an unwillingness to remain in such a trying environment.
In the United States people move to other regions for a variety of reasons including health, cost of living, job opportunities, and a change in lifestyles. But frequently older Americans seek to retire to states having milder weather. There has been a long trend for "northerners," to give up living in the cold, snowy tier of states to migrate to the warmer climes of Florida, Arizona, or California for a permanent residence. Victims of repeated river floods often relinquished their homes and moved en masse to higher locations, sometimes to far away locations. Tens of thousands of Plains farmers fled their farms for "greener pastures" in the western parts of America during the devastating Dust Bowl of the 1930s.
There remains a constant exodus from farm regions the world over due to crop failures brought on by the uncertainties of the weather,