A four-fold increase in the size of the world economy over the next 50 years will come at the expense of water shortages, rising pollution, dysfunctional cities and growing civic unrest, unless international leaders take urgent action at next week's World Summit on Sustainable Development, the World Bank warned last night.

In a stark message to the heads of state preparing to fly to Johannesburg, the bank said decisions must be taken over the next few years to halt the destruction of the environment and to share the benefits of economic growth more fairly to prevent its dystopian vision of the future becoming a reality.

"Action is required now - even for problems that will unfold over a longer period," said Jim Wolfensohn, the bank's president.

Fears that the 10-day summit will be a talking shop light on action have been heightened in recent days by the decision of President George Bush not to attend. Without the leader of the economy which consumes the largest share of the world's resources, green lobbyists are worried that the follow-up conference to the 1992 Rio Earth Summit will end with no real progress.

Tony Blair will only be at the summit for 24 hours, although Britain is sending four other ministers, including the deputy prime minister, John Prescott.

The issues on the table at Johannesburg - water shortages, global warming, bio-diversity and poverty - all require urgent decisions, the bank said in its annual world development report.

By 2050, the output of the world economy could have quadrupled in value to $140 trillion a year. While green activists argue that the environment cannot sustain human consumption on this scale, the Bank argues that a growing world economy is essential for lifting billions of people out of poverty and that it can be married with sustainable use of limited resources.

"If we are going to conquer poverty we have to have growth, and at a serious rate," said Nick Stern, the bank's chief economist. "If that is sustained over the next 50 years and environmental issues are not addressed, growth will be derailed."

The bank says that, despite the 2bn increase in the world's population over the last 30 years, there have been significant gains in human welfare.

"But the development path has left a legacy of accumulated environmental and social problems which cannot be repeated," said Mr Wolfensohn.

Humans are changing the world's climate, threatening coastal and island populations with rising sea levels and residents of semi-arid areas with desertification, according to the bank.

Hundreds of cities in developing countries have unhealthy air, causing premature deaths that would be preventable at a modest cost.

Developing countries are doing more to address cross-border environmental problems than industrialized countries did when they were at comparable stages of development, but, the bank said, lack of cash was forcing unnecessary trade-offs, generating environmental stresses.

"The key is to act now to initiate virtuous rather than vicious circles - to create constituencies for sustainability, not for environmental degradation and social polarization," the report said.

Two-thirds of the world's population will be living in cities by 2050, the bank predicted, and the demands of such vast urban conglomerates for housing, water and supplies will be vast.

But with better environmental standards and more efficient economic growth, the needs of the world's new cities can be managed, the Bank said.

"By thinking long term and acting now, we can take advantage of these windows of opportunity to shift development to a more inclusive and sustainable path," the report said.

© Guardian Newspapers Limited 2002

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