Parts of the world may have to be abandoned because severe water shortages will leave them uninhabitable, the United Nations environment chief has warned. Achim Steiner, executive director of the UN Environment Programme, said water shortages caused by over-use of rivers and aquifers were already leading to serious problems, even in rich nations. With climate change expected to reduce rainfall in some places and cause droughts in others, some regions could become 'economic deserts', unviable for people or agriculture, he said.

Steiner argued that only urgent action to combat global warming and poverty could prevent the creation of thousands of 'environmental refugees'. Previous UN agreements to reduce global warming emissions and the Millennium Development Goals on poverty had not been met. His warning echoes those of other environment leaders, who have said that water shortages could be the greatest threat posed by climate change.

'In many ways [water] is the most dramatic expression of mismanagement of natural or nature-based assets,' Steiner said. 'The day a person or a community is bereft of water is the day that your chance of even the most basic life or livelihood is gone and economic activity seeps away.

'Unchecked climate change will mean that some parts of the world will simply not have enough water to sustain settlements both small and large, because agriculture becomes untenable and industries relying on water can no longer compete or function effectively. This will trigger structural changes in economies right through to the displacement of people as environmental refugees.'

Steiner said it was not possible to identify specific places at risk, but said vulnerable areas were those which were already considered to be 'water scarce' because of dry weather and a lack of infrastructure to store and transport water. Last week a study of the water footprints of 200 nations led by conservation group WWF warned that 50 countries were already experiencing 'moderate to severe water stress on a year-round basis'.

This week experts from the UN Convention to Combat Desertification meeting in Turkey will warn that high food prices and endemic droughts are jeopardising the lives of hundreds of millions of people, particularly in Africa.

Some of the most dramatic examples of water shortages this year include conflict-stricken Sudan, the dramatic drying of Lake Faguibine in Mali on which 200,000 mostly nomadic people depend, fatal clashes over drying boreholes in northern Kenya, and economic and social crisis on the sparsely populated border between Bolivia and Argentina, according to Unep. Oxfam has estimated that 25 million people have been affected by the most recent drought in Ethiopia.

Rich nations are not immune. California has declared a state of emergency over water shortages, Australia has committed billions of dollars to cope with drought, and governments in Europe have been forced to ship in water to stop communities running dry.

'A plant, never mind a human being, simply cannot live without water,' said Steiner. 'It's not a matter of how we can live for three years without some water; these are not the kind of things we can do for a while and recover.

'In rich countries, there's always the potential of channelling water from one river basin to another. But even there people are hitting the limits of what we can do with money and infrastructure because there simply isn't enough water any more.'

Suggested solutions include better enforcement of restrictions on over-use of rivers, lakes and aquifers, more efficient use of water and increases in technologies to recycle and desalinate water.

Experts at the International Water Association congress in September called for investment in water infrastructure to at least double from the current level of $80bn (£49bn) a year to avoid widespread flooding, drought and disease. Unep has calculated that enough rain falls on Africa to theoretically supply the needs of 13 billion people, and has called for a continent-wide rainwater harvesting programme.

(Por Juliette Jowit, The Guardian, 02/11/2008)