The world needs to act urgently to avoid a global water crisis due to increased population, rising living standards, dietary changes and more biofuels production, the United Nations warned on Thursday.

By 2030, nearly half of the world's people will be living in areas of acute water shortage, said a report jointly produced by more than two dozen U.N. bodies and issued ahead of a major conference on water to be held in Istanbul next week.

The report, Water in a Changing World, made clear that urgent action is needed if we are to avoid a global water crisis, said a foreword by Koichiro Matsuura, head of the U.N. Educational, Scientific and Cultural Organization (UNESCO).

Despite the vital importance of water to all aspects of human life, the sector has been plagued by a chronic lack of political support, poor governance and underinvestment.

As a result, hundreds of millions of people around the world remain trapped in poverty and ill health and exposed to the risk of water-related disasters, environmental degradation and even political instability and conflict, Matsuura said.

U.N. Secretary-General Ban Ki-moon has repeatedly identified water shortage as a major underlying cause of the conflict in Darfur, western Sudan, which began with a rebellion against the central government six years ago. Water is also a major issue between Israel and its Arab neighbors.

The world's population of 6.6 billion is forecast to rise by 2.5 billion by 2050, with most of the growth in developing countries, many in regions where water is already scarce.

The growth rate means demand for fresh water is increasing by 64 billion cubic meters a year, the report said. Authors told a news conference that most of North Africa and the Middle East had already reached the limits of their water resources.


Migration from the countryside to cities was also increasing water use, the 318-page report said, as was growing consumption of meat -- the production of which requires more water than vegetables -- in China and elsewhere.

The report added to recent U.N. warnings about the downsides of developing biofuels to replace heavily polluting hydrocarbons as an energy source, because of the water needed to grow crops like corn and sugar cane to produce ethanol.

Saying about 2,500 liters of water is needed to make 1 liter of biofuel, it said implementing all current national biofuel policies and plans would take 180 cubic kilometers of extra irrigation water and 30 million hectares of cropland.

The impact could be large for some countries, including China and India, and for some regions of large countries, such as the United States, it said. There could also be significant implications for water resources, with possible feedback into global grain markets.

When oil prices peaked at over $140 a barrel last year, the kneejerk reaction was 'well, we are going to grow our energy - biofuels.' But nobody took account of how much water it was going to require, William Cosgrove, coordinator of the report, told journalists.

On the positive side, the report pointed to successful water policies in Uganda and Turkey and said a U.N. goal of halving the population lacking access to safe drinking water by 2015 would be achieved except in sub-Saharan Africa.

But it said in many countries water policies failed to make any impact because key decisions affecting water were made in other sectors of the economy.

Government and business leaders needed to act now to boost investment in water infrastructure, it said, adding, Unsustainable management and inequitable access to water resources cannot continue.