WWI: popolazione e acqua

["AlessandroGimona"<agimona@libero.it>]

Saggio di Lester Brown (World Watch Institute)

spero interessi,
saluti 
Alessandro Gimona


POPULATION GROWTH SENTENCING MILLIONS
  TO HYDROLOGICAL POVERTY

  Lester R. Brown

  At a time when drought in the United States, Ethiopia, and Afghanistan 
is in
  the news, it is easy to forget that far more serious water shortages 
are
  emerging as the demand for water in many countries simply outruns the 
supply.
  Water tables are now falling on every continent. Literally scores of 
countries
  are facing water shortages as water tables fall and wells go dry.
  We live in a water-challenged world, one that is becoming more so each 
year
  as 80 million additional people stake their claims to the Earth's 
water
  resources. Unfortunately, nearly all the projected 3 billion people to 
be added
  over the next half century will be born in countries that are already
  experiencing water shortages. Even now many in these countries lack 
enough water
  to drink, to satisfy hygienic needs, and to produce food.
  By 2050, India is projected to add 519 million people and China 211 
million.
  Pakistan is projected to add nearly 200 million, going from 151 
million at
  present to 348 million. Egypt, Iran, and Mexico are slated to increase 
their
  populations by more than half by 2050. In these and other water-short 
countries,
  population growth is sentencing millions of people to hydrological 
poverty, a
  local form of poverty that is difficult to escape.
  Even with today's 6 billion people, the world has a huge water 
deficit.
  Using data on overpumping for China, India, Saudi Arabia, North 
Africa, and the
  United States, Sandra Postel, author of Pillar of Sand: Can the 
Irrigation
  Miracle Last?, calculates the annual depletion of aquifers at 160 
billion cubic
  meters or 160 billion tons. Using the rule of thumb that it takes 
1,000 tons of
  water to produce 1 ton of grain, this 160-billion-ton water deficit is 
equal to
  160 million tons of grain or one half the U.S. grain harvest.
  At average world grain consumption of just over 300 kilograms or one 
third
  of a ton per person per year, this would feed 480 million people. 
Stated
  otherwise, 480 million of the world's 6 billion people are being fed 
with grain
  produced with the unsustainable use of water.
  Overpumping is a new phenomenon, one largely confined to the last half
  century. Only since the development of powerful diesel and 
electrically driven
  pumps have we had the capacity to pull water out of aquifers faster 
than it is
  replaced by precipitation.
  Some 70 percent of the water consumed worldwide, including both that
  diverted from rivers and that pumped from underground, is used for 
irrigation,
  while some 20 percent is used by industry, and 10 percent for 
residential
  purposes. In the increasingly intense competition for water among 
sectors,
  agriculture almost always loses. The 1,000 tons of water used in India 
to
  produce 1 ton of wheat worth perhaps $200 can also be used to expand 
industrial
  output by easily $10,000, or 50 times as much. This ratio helps 
explain why, in
  the American West, the sale of irrigation water rights by farmers to 
cities is
  an almost daily occurrence.
  In addition to population growth, urbanization and industrialization 
also
  expand the demand for water. As developing country villagers, 
traditionally
  reliant on the village well, move to urban high-rise apartment 
buildings with
  indoor plumbing, their residential water use can easily triple.
  Industrialization takes even more water than urbanization.
  Rising affluence in itself generates additional demand for water. As 
people
  move up the food chain, consuming more beef, pork, poultry, eggs, and 
dairy
  products, they use more grain. A U.S. diet rich in livestock products 
requires
  800 kilograms of grain per person a year, whereas diets in India, 
dominated by a
  starchy food staple such as rice, typically need only 200 kilograms. 
Using four
  times as much grain per person means using four times as much water.
  Once a localized phenomenon, water scarcity is now crossing national 
borders
  via the international grain trade. The world's fastest growing grain 
import
  market is North Africa and the Middle East, an area that includes 
Morocco,
  Algeria, Tunisia, Libya, Egypt, and the Middle East through Iran. 
Virtually
  every country in this region is simultaneously experiencing water 
shortages and
  rapid population growth.
  As the demand for water in the region's cities and industries 
increases, it
  is typically satisfied by diverting water from irrigation. The loss in 
food
  production capacity is then offset by importing grain from abroad. 
Since 1 ton
  of grain represents 1,000 tons of water, this becomes the most 
efficient way to
  import water.
  Last year, Iran imported 7 million tons of wheat, eclipsing Japan to 
become
  the world's leading wheat importer. This year, Egypt is also projected 
to move
  ahead of Japan. Iran and Egypt have nearly 70 million people each. 
Both
  populations are increasing by more than a million a year and both are 
pressing
  against the limits of their water supplies.
  The water required to produce the grain and other foodstuffs imported 
into
  North Africa and the Middle East last year was roughly equal to the 
annual flow
  of the Nile River. Stated otherwise, the fast-growing water deficit of 
this
  region is equal to another Nile flowing into the region in the form of 
imported
  grain.
  It is now often said that future wars in the region will more likely 
be
  fought over water than oil. Perhaps, but given the difficulty in 
winning a water
  war, the competition for water seems more likely to take place in 
world grain
  markets. The countries that will "win" in this competition will be 
those that
  are financially strongest, not those that are militarily strongest.
  The world water deficit grows larger with each year, making it 
potentially
  more difficult to manage. If we decided abruptly to stabilize water 
tables
  everywhere by simply pumping less water, the world grain harvest would 
fall by
  some 160 million tons, or 8 percent, and grain prices would go off the 
top of
  the chart. If the deficit continues to widen, the eventual adjustment 
will be
  even greater.
  Unless governments in water-short countries act quickly to stabilize
  population and to raise water productivity, their water shortages may 
soon
  become food shortages. The risk is that the growing number of 
water-short
  countries, including population giants China and India, with rising 
grain import
  needs will overwhelm the exportable supply in food surplus countries, 
such as
  the United States, Canada, and Australia. This in turn could 
destabilize world
  grain markets.
  Another risk of delay in dealing with the deficit is that some 
low-income,
  water-short countries will not be able to afford to import needed 
grain,
  trapping millions of their people in hydrological poverty, thirsty and 
hungry,
  unable to escape.
  Although there are still some opportunities for developing new water
  resources, restoring the balance between water use and the sustainable 
supply
  will depend primarily on demand-side initiatives, such as stabilizing 
population
  and raising water productivity.
  Governments can no longer separate population policy from the supply 
of
  water. And just as the world turned to raising land productivity a 
half century
  ago when the frontiers of agricultural settlement disappeared, so it 
must now
  turn to raising water productivity. The first step toward this goal is 
to
  eliminate the water subsidies that foster inefficiency. The second 
step is to
  raise the price of water to reflect its cost. Shifting to more 
water-efficient
  technologies, more water-efficient crops, and more water-efficient 
forms of
  animal protein offer a huge potential for raising water productivity. 
These
  shifts will move faster if the price of water more closely reflects 
its value.

  Copyright 2000 Worldwatch Institute www.worldwatch.org

  For additional data and information, see www.worldwatch.org/chairman/


Alessandro Gimona
agimona@libero.it