Humanity's Growing Impact on the World's Freshwater
It takes water to make everything, and the explosion of
demand for all manner of products is draining rivers, shrinking lakes
and depleting aquifers.
As the human population has climbed
past seven billion, and the consumption per person of everything from
burgers to blue jeans has risen inexorably, the finiteness of Earth’s
freshwater is becoming ever more apparent.
It
takes water to make everything, and the explosion of demand for all
manner of products is draining rivers, shrinking lakes, and depleting
aquifers.
Consider this: on average it takes
2,700 liters (713 gallons) to make a cotton shirt and
9,800 liters (2600 gallons) to make a pair of blue jeans. The cotton
crops growing in farmers’ fields consume most of that water; a smaller
share is used in the factories that churn out the clothes.
On
any given day we’re likely wearing more than 15,000 liters (~4,000
gallons) worth of water. And if we slip on a pair of leather loafers,
well, add another 8,000 liters (~2,100 gallons). It takes a lot of
water to grow the grain to feed the cow whose skin is turned into shoes.
Such
figures might not matter if there was abundant water whenever and
wherever we needed it – or if water had a substitute. But water is
limited, and there’s no substitute for it. We need water to quench our
thirst, to grow our food, to cool electric power plants, and to make
cars, computers and all those cotton shirts.
And that’s why the size of humanity’s water footprint – and of yours and mine – matters.
In a
study published this week in
the Proceedings of the National Academy of Sciences, researchers Arjen
Hoekstra and Mesfin Mekonnen of the University of Twente in the
Netherlands, have made the most detailed estimate to date of the scale
and patterns of humanity’s water consumption.
This
is a tricky and complicated task. Using a high level of spatial
resolution, the researchers tabulated all the water from both rainfall
and irrigation that’s consumed in making goods and services for the
global population. To complete the picture, they added in the volume of
water needed to assimilate the pollution generated along the way. They
calculated the annual average global footprint for 1996-2005, the most
recent ten-year period for which the necessary data were available.
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