Wars and economic reasons play the biggest role in the movement of people within their own country, but soon climate change will play its own role in these movements.
By 2050, 140 million people may be forced to migrate internally due to the impact of global warming, which will exacerbate problems such as water scarcity, crop damage, rising sea levels and storm hurricanes, according to a recent report.
The World Bank report, "Flood: Preparedness for Internal Climate Migration", analyzes the impacts of climate change on three regions: sub-Saharan Africa, South Asia and Latin America, a group that accounts for 55 percent of the developing world's population.
The report warns that failure to take the necessary steps will exacerbate the global asylum crisis in the future and that governments need to develop a plan for communities and people who will have to leave their homes because of the problems posed by climate change.
"Without an appropriate plan or adequate support, the migration of people from remote and rural areas to cities will face new and more serious problems," said Kantha Kumari Regu, the group's team leader who prepared the report.
"We may see increasing rates of tension and conflict as a result of increased pressure on scarce resources, but this future is not inevitable." Internal migrations may be a reality, but they will not be catastrophic if we start planning them now.
Hottest climate migration regions
The report identifies some of the "hottest areas" where people are likely to move in or out: Bangladesh, Ethiopia and Mexico because of climate change.
In Ethiopia, people are expected to move from the northern highlands due to poor crop production, as well as from Addis Ababa, because of the increasing water shortage. Migrants are likely to move to the southern highlands or secondary cities in the east.
People in Bangladesh are expected to migrate from the northeast and around Dhaka because of rising temperatures and a worsening flood problem.
Of the three countries, Mexico is the most prolific. People from low-lying flood-prone areas on the South Coast, as well as from the arid north, are expected to reach the country's central plateau, where Mexico City and other urban areas are located.
This report follows studies linking the civil war in Syria with climate change, a review of what is coming in light of the migration induced by climate change.