Writing in Scientific American several years ago, former Environmental Protection Agency chief William Ruckelshaus took a visionary look at what humanity would have to do to use natural resources at a never-ending rate. Moving to sustainability, he wrote, ``would be a modification of society comparable in scale to only two other changes: the agricultural revolution of the late Neolithic and the Industrial Revolution of the past two centuries. Those revolutions were gradual, spontaneous and largely unconscious,'' he went on. ``This one will have to be a fully conscious operation, guided by the best foresight that science can provide - foresight pushed to its limit. If we actually do it, the undertaking will be absolutely unique in humanity's stay on the earth.''
In recent years, just about every politician, bureaucrat, business executive, academic, and activist has jumped on the ``sustainability'' bandwagon. Depending on one's political, philosophical, and even religious leanings, the word can mean different things. Still, it comes down to balancing environmental protection with economic development in a way that can go on forever.
In San Francisco last week, ecologist David Pimentel presented a sobering view of what the world will be like a century from now if that doesn't happen - and the drastic steps necessary to seeing that it does.
In a paper given at the annual meeting of the American Association for the Advancement of Science, Dr. Pimentel and four colleagues at Cornell University drew on the findings of government and private studies to conclude that in order to achieve and maintain a decent standard of living for everybody, the world's population will have to be reduced to less than half its current total.
It is a Malthusian message reminiscent of ``The Population Bomb'' and ``Limits to Growth'' - two jeremiads of earlier years that were very controversial, even ridiculed for prophesying doom that did not occur. But it may well be that those earlier warnings (and more recent ones like ``Beyond the Limits'' and the regular reports of the Worldwatch Institute) were just ahead of their time, that the essence of their argument is correct and the only real quibble is over timing.
Pimentel's message is compelling. At current growth rates, world population will expand from 5.6 billion to 8.4 billion 30 years from now and perhaps 15 billion by the end of the next century. Developed countries like the United States will continue to grow, but the great bulk of the increase will come in poorer nations. This is not theory but simple mathematics.
Meanwhile, the evidence of depletion and degradation in the resources on which all rely is mounting. When looked at in the aggregate, productive arable land, water, energy sources, the biodiversity that indicates a healthy ecosystem - all are in decline. Such assertions are based on quantifiable data like falling water tables, deforestation, and rates of soil erosion.
The result of steadily growing population and declines in the basics of survival - food, water, and energy - is that 1.6 billion people already are malnourished and from 1.2 to 2 billion live in poverty. This leads Pimentel and his colleagues to conclude with a question: ``Does human society want 10 to 15 billion humans living in poverty and malnourishment or 1 to 2 billion living with abundant resources and a quality environment?''
Some argue that there are promising technological answers out there. Genetic farming to produce more food with fewer chemicals. Cheap new sources of power like fusion. More efficient ways of using water and energy. Governments are putting more effort into exploring and developing these possibilities, and that's good. But suppose these don't deliver the way their boosters hope they will. Suppose the next scientific fix ends up like the ``green revolution'' - providing more crops for some while the overall number of hungry persons increases (and unintended harmful side effects result as well). Any answer must include a steady reduction in population growth rates. Otherwise the ``fully conscious'' revolution Mr. Ruckelshaus says is necessary to achieve real sustainability will never occur.