Major cities should focus efforts and funds on conserving forests which naturally purify their drinking water, saving them from spending billions of dollars on water treatment facilities, according to a study published this week.
The study of 105 big cities by the World Bank and the ecology organization the World Wide Fund for Nature (WWF) showed that one-third of them, including New York, Tokyo, Barcelona and Melbourne, get much of their water via protected forests.
Preserving these forests which reduce landslides, erosion and sediment; improve water purity by filtering pollutants, and in some cases capture and store water is a cost-effective way to provide clean drinking water, the study "Running Pure" said.
"For many cities, time is running out. Protecting forests around water catchment areas is no longer a luxury but a necessity," said David Cassells, senior environmental specialist for forest resources with the World Bank.
"When they are gone, the costs of providing clean and safe drinking water to urban areas will increase dramatically."
Chris Elliot, director of WWF's Forests for Life Program, highlighted the stark case of New York, whose nine million residents get much of their water from the Catskill/Delaware watersheds in upstate New York.
A recent evaluation showed it would cost $7 billion to build a water treatment plant against a $1 billion bill for actively managing New York's forest catchment area by raising water taxes and paying farmers to use less fertilizer and reduce grazing.
Forest preservation is a proven method of improving water quality "down under." Dubbed "Smellbourne" in the 18th century because of its poor water quality, Melbourne took measures to protect the mountainous forest catchments to its north and east. Today these supply 90 percent of the drinking water in Melbourne, now recognized as having the highest quality water of any Australian city.
Cassels added that managing the forests should not be at the expense of people living in the areas, and users who benefit from the forests should pay toward conserving them.
Authorities face difficult choices between building houses for growing populations, chopping down forests for timber, or conserving them to help secure the water supply, Elliot said.
But given World Health Organization estimates that 1.1 billion people do not have access to clean drinking water and that waterborne diseases claim five million lives each year, the WWF is calling on governments to boost their conservation efforts in water catchment areas.
Jamie Pittock, director of WWF-International's Living Waters program, argued that protection would help countries achieve their aim of halving the number of people without access to safe drinking water by 2015.
"These global targets can be most effectively achieved, in part, by investing in the health of these forest water catchments," he said. "By securing the source of the water, by investing in the health of the environment through these protected areas we can make a big difference to people's lives."