As the U.N. climate change meetings meander on in Durban, South Africa, with little sign of major breakthrough -- and soon after news that the last year saw the largest rise in carbon emissions in history -- it is a good time to think about how to deal with some of the impacts of a global warming that appear increasingly inevitable. One big impact involves water -- both that there's soon going to be too much of the salty stuff subsuming low lying areas as the ice caps melt, and too little elsewhere. A warmer world will be wetter overall, but current models predict that climate change will make some dry parts of the planet -- Northern Africa, for one -- even drier. Many of the places are already the very regions suffering from the greatest shortages. Even without climate change, global patterns of water usage are unsustainable, but global warming is a big reason to start using the stuff with greater care. The simplest way to encourage that? Make people pay for it.
Water is essential stuff, and sometimes we're willing to price it accordingly. How else to explain why U.S. consumers spend $7 billion on bottled water a year when they can't tell the difference with what comes out of the tap in taste tests -- and despite the fact it often costs more than three times as much per gallon than gas. But at other times we demand, like air, that it should be free -- or at least significantly subsidized. Farmers in California alone received about $236 million per year in effective subsidies from access to cheap water in the 1990s, for example. But California is far from the worst example of subsidizing unsustainable water use worldwide. And unless we start charging consumers what it costs to deliver piped water, many parts of the planet are simply going to run out -- even absent the impacts of climate change. Meanwhile, the world's poor consumers, mostly unconnected to piped delivery, will continue to pay considerably more for their water than the connected rich -- adding inequity to unsustainability as a cost of mispricing the stuff.
One-third of the world's population already faces water shortages. A recent McKinsey report estimates that based on current trends, by 2030, a third of the world will live in areas where the gap between water needs and accessible, reliable supply is greater than 50 percent -- so they'll have to be planting and drinking on borrowed time by that point. Agriculture is the big problem -- irrigation of cropland is responsible for 71 percent of freshwater needs worldwide, and accounts for over 93 percent of the freshwater we take out of rivers, lakes, and the ground and cannot then clean and re-use, according to the World Bank. By 2030, without efficiency improvements, global water requirements will climb from 4,500 cubic kilometers (about the volume of Lake Michigan) to 6,900 cubic kilometers each year -- largely thanks to the growing demand for food. That is some 40 percent above current accessible, reliable supply.
The picture is not that grim, however. For a start, we have seen a 1 percent improvement in efficiency in water use in agriculture per year in the period 1990-2004, alongside irrigation network growth that has occurred at a similar pace. If these trends continue, between them, these may address 40 percent of the gap between supply and demand in 2030, according to McKinsey.
Second, there are a number of methods to dramatically, and very cheaply, increase water efficiency at a considerably more aggressive rate than 1 percent a year. No-till farming, irrigation scheduling, reduced over-irrigation, and irrigated drainage all can have a dramatic impact. And a number of water-saving investments are very cheap -- including proper maintenance and repair as well as the use of drip irrigation. McKinsey estimates the total global cost to close the 2030 water gap to be $50-$60 billion a year -- around 0.06 percent of the world's predicted gross domestic product that year.