One way would be to limit who can receive a passport or visa to travel to another country and another would be at the entrance to the country they may not be admitted for example due to inadequate funds to live. In my case, when I travelled by bus from Costa Rica to Panama, the Panamanian authorities required that I either have a ticket out of the country or a return ticket back to San Jose, Costa Rica.
It depends on the map. There should be a key indicated.
It causes for the world climate to rise causing global warming. Also erosion causes be buildings to be eaten away from water or acid rain and can destroy homes and possible hurt humans. Deposition runs into the water and streams with eventually goes to the water lines to the food and drinks we consume today.