A decade of discontinuity.

• Author: Brown, Lester R.

The 1980s may have been the last decade in which humankind could anticipate a future of ever-increasing productivity on all fronts. By one measure after another, the boom we have experienced since mid-century is coming to an end.

When the history of the late 20th century is written, the 1990s will be seen as a decade of discontinuity - a time when familiar trends that had seemed likely to go on forever, like smooth straight roads climbing toward an ever-receding horizon, came to abrupt bends or junctures and began descending abruptly. The world's production of steel, for example, had risen almost as reliably each year as the sun rises in the morning. The amount of coal extracted had risen almost uninterruptedly ever since the Industrial Revolution began. Since the middle of this century, the harvest of grain had grown even faster than population, steadily increasing the amount available both for direct consumption and for conversion into livestock products. The oceanic fish catch, likewise, had more than quadrupled during this period, doubling the consumption of seafood per person.

These rising curves were seen as basic measures of human progress; we expected them to rise. But now, within just a few years, these trends have reversed - and with consequences we have yet to grasp. Meanwhile, other trends that were going nowhere, or at most rising slowly, are suddenly soaring.

That such basic agricultural and industrial outputs should begin to decline, while population continues to grow, has engendered disquieting doubts about the future. These reversals, and others likely to follow, are dwarfing the discontinuities that occurred during the 1970s in the wake of the 1973 rise in oil prices. At that time, an overnight tripling of oil prices boosted energy prices across the board, slowed the growth in automobile production, and spurred investment in energy-efficient technologies, creating a whole new industry.

The discontinuities of the 1990s are far more profound, originating not with a handful of national political leaders as with the OPEC ministers of the 1970s, but in the collision between expanding human numbers and needs on the one hand and the constraints of the earth's natural systems on the other. Among these constraints are the capacity of the oceans to yield seafood, of grasslands to produce beef and mutton, of the hydrological cycle to produce fresh water, of crops to use fertilizer, of the atmosphere to absorb CFCs, carbon dioxide, and other greenhouse gases, of people to breathe polluted air, and of forests to withstand acid rain.

Though we may not have noticed them, these constraints drew dramatically closer between 1950 and 1990, as the global economy expanded nearly fivefold. Expansion on this scale inevitably put excessive pressure on the earth's natural systems, upsetting the natural balances that had lent some stability to historical economic trends. The trends were driven, in part by unprecedented population growth. Those of us born before 1950 have seen world population double. In 1950, 37 million people were added to the world's population. Last year, it was 91 million.

Against the Grain

The production of grain, perhaps the most basic economic measure of human well-being, increased 2.6 fold from 1950 to 1984. Expanding at nearly 3 percent per year, it outstripped population growth, raising per capita grain consumption by 40 percent over the 34-year period, improving nutrition and boosting consumption of livestock products - meat, milk, eggs, and cheese - throughout the world.

That period came to an end, ironically, around the time the United States withdrew its funding from the United Nations Population Fund. During the eight years since 1984, world grain output has expanded perhaps one percent per year. In per capita terms, this means grain production has shifted from its steady rise over the previous 34 years to a decline of one percent per year since then - a particularly troubling change both because grain is a basic source of human sustenance and because of the likely difficulty in reversing it (see Figure 1).

This faltering of basic foodstuffs was triggered by other, earlier discontinuities of growth - in the supply of cropland, irrigation water, and agricultural technologies. Cropland, measured in terms of grain harvested area, expanded more or less continuously from the beginning of agriculture until 1981. The spread of agriculture, initially from valley to valley and eventually from continent to continent, had come to a halt. Since 19 8 1, it has not increased. Gains of cropland in some countries have been offset by losses in others, as land is converted to nonfarm uses and abandoned because of erosion.

Irrigation, which set the stage for the emergence of early civilization, expanded gradually over a span of at least 5,000 years. After the middle of this century, the growth in irrigated area...