In a devastating assessment of the future for the human race in the early part of the next century Dr Klaus Topfer, the executive director of the UN environment programme, says that the main threats to human survival were posed by water shortages, global warming, and a new danger - worldwide nitrogen pollution.
"A series of looming crises and ultimate catastrophe can only be averted by a massive increase in political will. We have the technology but we are not applying it," he said.
Launching a report called Global Environment Outlook 2000 in London, Dr Topfer said it was possible to reverse the process but conspicuous over-consumption by the world's rich countries had to be cut by 90 per cent to do so. He said it did not mean a lowering of living standards but an application of existing science, through recycling, for instance.
"The developed world has the technology to bring about the fundamental changes needed to save millions of people from hunger, thirst and ill health. But there is no incentive to apply it because politicians are not forcing manufacturers to do so," he said.
There were signs that targets to cut greenhouse gases from industrialised countries by 5 per cent by 2010 under the Kyoto protocol would not be reached, Dr Topfer claimed.
He described efforts to curb global warming as inadequate, while 60 per cent cuts were required, and added that the world was already suffering as a result of climate change which was now unstoppable.
Extreme weather events had left 3 million people dead in the last five years, Dr Topfer said - the current US hurricane was an example of the destruction which was becoming more common because of climate change.
Dr Topfer, the former German environment minister, said: "It is possible to get very angry and dismayed about what we are doing to the world but it does not help. What matters is being constructive and realising that where there is political will, much can be achieved.
"For example in Europe we have defeated the menace of acid rain by reducing by 75 per cent the amount of sulphur dioxide released from factories since 1980. The worldwide reduction in the manufacture and use of CFCs has put us well on the way to curing the hole in the ozone layer. There are now salmon again in the Thames and the Rhine. We can do it if we try.
"We are improving things further with the urban waste water directive, which will give us cleaner rivers and beaches, but in other parts of the world 15 million children under five die each year from diseases caused by drinking unclean water.
"This could be prevented, but gains made by better management and technology are still being outpaced by degradation.
"Population continues to be a problem. In 1950 the population of Africa was half that of Europe. Now it is about equal. In 2050 it will be three times that of Europe. We have to change these trends."
A new problem identified by the report is nitrogen pollution. This is partly caused by untreated sewage from new cities, which pollutes water courses, but mainly by large increases in the use of artificial fertiliser to boost crop growth.
Dr Topfer added: "Many of the planet's species have already been lost or condemned to extinction. One quarter of the world's mammal species are now at significant risk of total extinction."