By 2050 how many people could become environmental refugees?
When people realised that landfills: encourage vermin (rats), emit methane gas (a dangerous greenhouse gas), use up valuable land, contain a lot of valuable items that could be recycled like glass, metals, aluminum and paper. Then people realised that landfills were an important environmental issue.
Whether or not to become a refugee was the decision of the individual. They could attempt to stay in their homes, but usually fled when the fighting got too close. In some places the soldiers would drive people out of their houses, or take them as prisoners and send them to concentration camps. The Allies would have civilians evacuate areas for their safety, but didn't prevent them from returning when it was safe.
It is not an issue of cost. People become refugees through circumstances. You could be living in a war zone and have your home completely destroyed and have to try to leave the country. You might have to do so on foot, grabbing whatever possessions you can take with you. It does not cost you money to become a refugee, but there can be costs in other ways, in the sense that your life is…