The world is running out of water and needs a radical plan to tackle shortages that threaten the ability of humanity to feed itself, according to Jeffrey Sachs, director of the UN's Millennium Project.
The breadbaskets of India and China were facing severe water shortages and neither Asian giant could use the same strategies for increasing food production that has fed millions in the last few decades.
"In 2050 we will have 9 billion people and average income will be four times what it is today. India and China have been able to feed their populations because they use water in an unsustainable way. That is no longer possible," he said.
The British government has been trying to persuade a reluctant New Delhi to embrace green technology. Officials in India still talk about the need for accelerating growth and see tackling climate change as a brake on the economy.
The United Nations said Tuesday that China has made progress in increasing access to water for its citizens but still faces serious challenges in fighting pollution.
Water pollution and a lack of clean drinking water are some of the most serious problems facing China, with most of its canals, rivers and lakes severely tainted by agricultural, industrial and household pollution.
"Pollution of water sources is widespread and increasingly serious in China. Meanwhile, more water is being used than is being replenished, which shows in falling groundwater tables and drying rivers," said Alessandra Tisot, senior deputy resident representative of the U.N. Development Program in China.
"As the needs of consumers, agricultural and industrial production are pitted against one another in a booming economy, these problems can be expected to grow worse, not better," Tisot told a news conference.