A new report from the World Bank says climate change will create the greatest human migration in history.
The report predicts that in the next three decades, 143 million people in sub-Saharan Africa, South Asia, and Latin America will be forced to leave their homes from rural to urban areas.
The reason is not a dramatic disaster like a storm or a flood, but the slower effects of climate change, such as sea level rise and prolonged drought.
In this study, the researchers selected three countries with very rapid population growth for case studies: Ethiopia, Bangladesh, and Mexico.
Unsurprisingly, they found that people at the bottom of the economy would be the first victims.
In Ethiopia where rainfall has declined over the last few years, people in the hilly north of the country have to leave the country in search of new cultivation land. Meanwhile, growth in Ethiopia's biggest city, Addis Ababa, also fell due to the reduced rainfall.
Conversely, rising sea levels and recurrent hurricanes are predicted to encourage populations in major cities of Bangladesh due to massive urbanization.
Mexico, which is the richest of the three countries, is better equipped to cope with climate change, but it also has to be careful of pockets of poverty. The areas around Mexico City and Guatemala are better climate can attract the arrival of climate migrants from other regions.
Although it sounds bad, the researchers believe that this is not the end result. If we try to reduce greenhouse gas emissions and make careful planning, then this massive migration will be reduced by 80 percent to 40 million people.
Kristalina Georgieva, CEO of the World Bank, says we have a narrow time before the effects of climate change worsen to make plans for this new reality.
The steps taken by big cities to prepare for the arrival of the rural areas and increase the opportunities for study and work will provide long-term dividends.