The government-commissioned report warns of potential humanitarian disasters because of climate change.
It says the cost of acting now would be much less than the cost of the conflicts and huge loss of life that would otherwise ensue.
The report focused on the issue of human migration patterns.
The Migration and Global Environmental Change Foresight Report is the most detailed study carried out on the effect of flooding, drought and rising sea levels on human migration patterns over the next 50 years.
The government’s chief scientist, Professor Sir John Beddington, who commissioned the study, said that environmental change would hit the world’s poorest the hardest and that millions of them would inadvertently migrate toward, rather than away from, areas that are most vulnerable.