The charity Christian Aid says the effects of climate change could make at least 1bn people homeless between now and 2050.
The group expects climate change to deepen an already worsening global migration crisis.
In a report to mark the start of Christian Aid week, the charity says that forced migration is now the most urgent threat facing poor people in the developing world.
It also fears that the wave of migrations will generate new conflicts in areas of the world where resources are most scarce.
