A billion people - one in seven people on Earth today - could be forced to leave their homes over the next 50 years as the effects of climate change worsen an already serious migration crisis, a new report from Christian Aid predicts. The report, which is based on latest UN population and climate change figures, says conflict, large-scale development projects and widespread environmental deterioration will combine to make life unsupportable for hundreds of millions of people, mostly in the Sahara belt, south Asia and the Middle East.

According to the development charity, the world faces its largest movement of people forced from their homes. "Forced migration is now the most urgent threat facing poor nations," said John Davison, the report's lead author. "Climate change is the great, frightening unknown in this equation." About 155 million people are known to be displaced now by conflict, natural disaster and development projects. This figure could be augmented by as many as 850 million, as more people are expected to be affected by water shortages, sea level crises, deteriorating pasture land, conflicts and famine, the report says.

The authors admit that the figures are uncertain "because there are no recent, authoritative global figures on the number of people who could be displaced by climate change". "But the lack of knowledge must not lead to a neglect of what can be done now to prevent displacement and to help people who are affected," says the report, which says the best way to reduce people's vulnerability would be to reduce global poverty.

It draws heavily on the latest Intergovernmental Panel on Climate Change (IPCC) report, which said that by 2080, 1.1-3.2 billion people would be experiencing water scarcity, 200-600 million hunger and 2-7 million a year coastal flooding. Western governments are increasingly aware of climate change as a security issue. Britain's foreign secretary, Margaret Beckett, has highlighted the threat of climate change to the UN security council and last week said it was an underlying factor in the Darfur crisis with the potential to escalate many other existing conflicts. "In climate change we have a new and potentially disastrous dynamic," she said.

The Christian Aid report says: "A staggering number of people are being pushed aside to make way for dams, roads and other large-scale development [projects]." It says this includes 25 million displaced by conflict and human rights abuses, 25 million by natural disasters, such as earthquakes, and 105 million by large development projects, with 8.5 million now officially classed as refugees.

By 2050, it says, twice as many people could be displaced by conflict and natural disasters, but 250 million could be permanently displaced by climate change-related phenomena such as droughts, floods and hurricanes, and 645 million by dams and other development projects, based on a current rate of 15 million people a year. "The growing number of disasters and conflicts linked to future climate change will push the numbers far higher unless urgent action is taken. We estimate that between now and 2050 a total of 1 billion people will be displaced from their homes."

(The Guardian, 14/05/2007)