The world is running out of water and needs a radical plan to tackle shortages that threaten humanity's ability to feed itself, according to Jeffrey Sachs, director of the UN's Millennium Project.
Professor Sachs, the renowned American economist who is credited with prompting pop star Bono's crusade for African development, told an environment conference in Delhi that the world had "no more rivers to take water from".
India and China were facing severe water shortages and neither could use the same strategies for raising food output which has fed millions in recent times. "In 2050 we will have 9 billion people and average income will be four times what it is today," he said. "India and China have been able to feed their populations because they use water in an unsustainable way. That is no longer possible."
Since Asia's agricultural revolution, the amount of land under irrigation has tripled. But many parts of the continent have reached the limits of water supplies. "The Ganges [in India] and the Yellow river [in China] no longer flow. There is so much silting up and water extraction upstream they are pretty stagnant."
Keep in mind they not only use this water for personal consumption and hygiene, but also for agriculture. Water is a limited resource, believe it or not. There aren't any natural processes that refresh the underground water supply fast enough for us to keep using it this way. Because of this, experts are saying that in the future some nations are going to have to have water shipped to them.
In Paris on Friday the world's top climate scientists issued the strongest warning yet that human activity was heating the planet. They forecast temperatures would rise by between 1.1 and 6.4 degrees Celsius this century.
By 2100, water scarcity could impact between 1.1 and 3.2 billion people, says a leaked, related U.N. climate study due to be published in April.
China and Australia, as well as parts of Europe and the United States would face critical water shortages, it says.
Daniel Zimmer, executive director of the World Water Council in Marseille, said there was a real prospect that fleets of dedicated tankers could shuttle fresh water between countries.
But he saw it only being feasible for essential supplies of fresh drinking water and not for low grade agricultural water where the cost of freight would outweigh the benefits.
"We definitely see it increasing. We expect in the future and even in the short-term, before 2050, more frequent heatwaves and dry periods which could make shipping water economically justifiable," he told Reuters.
He said exporting water by sea was already happening between France and Algeria and Turkey and Israel.
There is always the option of desalinating water, and if it gets bad enough I'm sure more nations will switch to that process. It is, however, energy intensive. Conservation is likely to be more effective in the long run than simply increasing our supply of water, thus enabling yet more over-population.
To put it bluntly, there are too many people in the world for us to use any resource at the rate we do individually. That means there are three solutions to the problem: increase our resources, decrease our population, or lower our resource consumption to a sustainable level. I'm for the latter two, since the first one is basically impossible (and I don't want to create a world where we pay for air anyway). I think it's immoral for anyone to claim the right to have as many children as they want when the simple fact of having more than the replacement rate (2 kids per couple) makes it that much more difficult for their children to have children (who'll survive anyway). Even if we lower energy consumption, at the rate we're going now, 6 billion people are too many for the planet. In 100 years, when our population may be more than 12 billion, even if those people use energy at half the rate we do, it'll still be too much! We're making life harder on the people of the future, and that's not right. So take some time to go to the store and get some fluorescent bulbs, use a higher efficiency shower-head, lower the level of water in your toilet, don't stand in front of the fridge with your door open, etc, etc. It's the least you can do.