The past half-century was marked by unprecedented population growth, driving fundamental environmental changes, and by dramatic growth in interdependence among nations for the necessities of life. The next half century will be shaped in considerable measure by the enormous differences in fertility and population growth between the developed and developing worlds. The resulting instabilities will be magnified by the extent to which open trading systems have made nations interdependent, but the instabilities have their origin in demographic change. They can be avoided or at least ameliorated if population growth in the less developed world (the LDCs) and the United States is halted and reversed. Despite its appearance of awful inevitability, that growth can be reversed, but it will require a new mindset that recognizes continuing population and economic growth as a threat rather than a blessing.

Much of human activity can be characterized as accidental experiments. It is a useful metaphor. We do things to our environmental support systems without realizing it — or indeed much caring. The growth of human populations and consumption in the past two generations, the transformation of agriculture, the multiplication of new chemicals, and the growth of fossil energy use are all interconnected. They have not been seen as a whole, and they are not sustainable.

The vastest of these experiments gathered force in the 1950s. Modern medicine and public health practices sharply reduced mortality in the poor countries. The motive was humane. We all can applaud a reduction of mortality. But when we tampered with one side of a natural equation without changing the other side, we generated a fundamental imbalance. Efforts to address human fertility were delayed, timid and faltering. Consequently, the world’s population grew much more in the following two generations than it had in all previous human history. The poorer, less developed countries (LDCs) nearly trebled from 1.7 billion in 1950 to 4.9 billion in 2000. The United States’ population, driven increasingly by immigration, nearly doubled from 151 million to 281 million. The rest of the industrial world (DCs) grew by 37 percent, to 910 million. (UN2000)

Concurrently, there has been a consumption boom unparalleled in human history. The combination has led to hitherto unknown pressures on resources and productive systems. For the first time, humans now dominate most ecosystems and affect all of them.