But not a drop to drink

January 07, 1994|By Robert Engelman

IN THE long debate over population and resources, food has '' drawn the most attention -- and the worst forecasts. From Thomas Malthus in 1798 to Paul Ehrlich in 1968, predictions of imminent famine have been off the mark. Human ingenuity so far has managed to come up with new ways to out-reap the Grim Reaper in the global harvest.

Dodging a bullet, however, is no guarantee of immortality. Perhaps a better example of a finite natural resource pressed to its limits by population growth is the fresh water all human beings need for health and survival. Lack of access to safe water is a daily problem for many people in the developing world, but in the past year concerns about the safety of drinking water have led Americans to shun their taps in Milwaukee, Des Moines and -- last month -- the nation's capital.

Difficult to purify, expensive to transport and impossible to substitute, renewable fresh water may be the most unforgiving of the planet's natural resources. About 10,000 cubic miles of renewable fresh water move through the hydrological cycle each year, a small fraction of all the Earth's water and a volume relatively unchanged throughout human history.

World population, however, has expanded from a few million in prehistoric times to 5.5 billion today, with increases in per capita water consumption that further strain the water cycle. It's a renewable resource; we can't run out of it. But we can spread it so thin that health and development are stymied. And that's what increasingly is happening as many countries drop below widely recognized benchmarks of per capita water availability needed for health and development.

Today, from the deserts of Saudi Arabia to the Texas panhandle, the expansion of irrigated agriculture is drawing on non-renewable groundwater to feed the world. In many nations in Africa, reservoir and lake levels are falling and water tables are dropping, leaving wells dry as greater numbers of users press on limited supplies. For some countries with rapidly expanding populations, the danger is that now-abundant non-renewable water resources eventually will be sucked dry. Much more modest renewable resources would then be pressed to support populations that could not have grown so numerous in the absence of non-renewable water.

There are many terms for what happens when population growth races past critical natural thresholds of resource availability, including "overshoot" and "population crash." A less alarmist and more accurate term describes water use in much of today's world: unsustainable.

In 1955, only seven countries with a combined population of just 3.7 million people qualified as water-scarce. Within 35 years, in 1990, the number of water-scarce nations had nearly tripled, to 20, and the number of people living in such countries had multiplied 35 times, to 131 million. In another 35 years, by United Nations projections, the numbers will rise to between 817 million and 1.079 billion -- about an eighth of the world's population -- in 30 to 34 countries.

Fully one-third of humanity will live in countries -- concentrated in the Middle East and Africa but scattered across the globe -- that experience either water stress or water scarcity by 2025.

The implications of water scarcity for health are ominous, as necessity forces people to use water of any quality available. Nearly half the world's population suffers from water-borne diseases, from chronic diarrhea to cholera. And international campaigns to expand safe water supply and sanitation services continue to fall behind the growth in human numbers.

Among the most worrisome implications of growing water scarcity is its potential for sparking or exacerbating national and regional conflict. Competition for fresh water figured in the 1967 Arab-Israeli conflict, and the issue remains to be resolved in the Middle East peace process. Worldwide, over 200 river and lake basins are bordered by two or more countries, and at least 10 rivers flow through a half-dozen countries or more. Water increasingly will become a source of tension and focus of diplomacy.

No single measure or approach is likely to slow or reverse the spread of water scarcity. Market pricing can't accomplish much, because little of the world's fresh water is metered. Desalination works well -- for those few nations with few people and plenty of money, plenty of energy and access to a seacoast. Unfortunately, humanity cannot expand the supply of renewable water. And because the number of couples of reproductive age now expands by nearly 18 million each year, considerable population growth will unavoidably put more pressure on the planet's water cycle.

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