Scores of countries face war for scarce land, food and water as global warming increases. This is the conclusion of the most devastating report yet on the effects of climate change that scientists and governments prepare to issue this week.

More than 60 nations, mainly in the Third World, will have existing tensions hugely exacerbated by the struggle for ever-scarcer resources. Others now at peace - including China, the United States and even parts of Europe - are expected to be plunged into conflict. Even those not directly affected will be threatened by a flood of hundreds of millions of "environmental refugees".

The threat is worrying world leaders. The new UN Secretary General, Ban Ki-moon, told a global warming conference last month: "In coming decades, changes in the environment - and the resulting upheavals, from droughts to inundated coastal areas - are likely to become a major driver of war and conflict."

Margaret Beckett, the Foreign Secretary, has repeatedly called global warming "a security issue" and a Pentagon report concluded that abrupt climate change could lead to "skirmishes, battles and even war due to resource constraints".

The fears will be increased by the second report this year by the Intergovernmental Panel on Climate Change. The result of six years' work by 2,500 of the world's top scientists, it will be published on Good Friday.

The first report, released two months ago, concluded that global warming was now "unequivocal" and it was 90 per cent certain that human activities are to blame. The new one will be the first to show for certain that its effects are already becoming evident around the world.

Tomorrow, representatives of the world's governments will meet in Brussels to start four days of negotiation on the ultimate text of the report, which they are likely to tone down somewhat.

But the final confidential draft presented to them by the scientists makes it clear that the consequences of global warming are appearing far sooner and faster than expected. "Changes in climate are now affecting biological and physical systems on every continent," it says.

In 20 years, tens of millions more Latin Americans and hundreds of millions more Africans will be short of water, and by 2050 one billion Asians could face water shortages. The glaciers of the Himalayas, which feed the great rivers of the continent, are likely to melt away almost completely by 2035, threatening the lives of 700 million people.

Though harvests will initially increase in temperate countries - as the extra warmth lengthens growing seasons - they could fall by 30 per cent in India, confronting 130 million people with starvation, by the 2050s.

By 2080, 100 million people could be flooded out of their homes every year as the sea rises to cover their land, turning them into environmental refugees. And up to a third of the world's wild species could be "at high risk of irreversible extinction" from even relatively moderate warming.

International Alert, "an independent peace-building organisation", has complied a list of 61 countries that are already unstable or have recently suffered armed conflict where existing tensions will be exacerbated by shortages of food and water and by the disease, storm flooding and sea-level rise that will accompany global warming, or by the deforestation that helps to cause it. The list forms the basis of the map on the opposite page.

Four years ago the Pentagon report concluded: "As famine, disease and weather-related disasters strike... many countries' needs will exceed their carrying capacity. This will create a sense of desperation, which is likely to lead to offensive aggression."

Many experts believe this has begun. Last year John Reid, the Home Secretary, blamed global warming for helping to cause the genocide in Darfur. Water supplies are seen as a key cause of the Arab-Israeli conflicts. The Golan Heights are important because they control key springs and rivers and the Sea of Galilee, while vital aquifers lie under the West Bank.

John Ashton, the Government's climate change envoy, says that global warming should be addressed "not as a long-term threat to our environment, but as an immediate threat to our security and prosperity".
(By Geoffrey Lean - The Independent, 01/04/2007)