The warming earth and the globalisation of the consumer society are becoming the biggest threats to future wealth and happiness, the United Nations said.

Rich countries “need to blaze the trail” on making economic growth less dependent on fossil fuels and helping poor nations get onto the path of sustainable development, said the annual Human Development Report.

Highlighting the failure of last year’s Copenhagen climate summit, it called for international commitment at events such as the new UN-sponsored climate talks in Cancun, Mexico next month “if we are to face up to what may be the most serious threat the world has ever faced”.

The report – The Real Wealth of Nations – says that overall most of the world has become wealthier, healthier and better educated over the past 20 years that the study has been released.

But it added: “The main threat to maintaining progress in human development comes from the increasingly evident unsustainability of production and consumption patterns.”

“Increased exposure to drought, floods and environmental stress is a major impediment to realising people’s aspirations,” said the UN Development Programme study.

With the world population expected to hit nine billion by 2050 and incomes rising, pressure on energy and fuel sources will grow, the report said.

“Climate change may be the single factor that makes the future very different, impeding the continuing progress in human development that history would lead us to expect.

The report said one estimate that wheat prices could double would have “massive repercussions”.

In a worst case scenario, by 2050 per capita consumption of cereals could fall by a fifth leaving 25 million additional children malnourished with South Asia the worst affected, it said.

With the international financial crisis still being felt, “the continuing reliance on fossil fuels is threatening irreparable damage to our environment and to the human development of future generations”, said the report.

“These developments pose serious questions about the long run feasibility of the world’s current production and consumption patterns.”