The Problem Is Simple: Too Many People, Too Much Stuff

By Paul & Anne Ehrlich, Yale Environment 360. Posted August 7, 2008.

Over some 60 million years, Homo sapiens has evolved into the dominant animal on the planet, acquiring binocular vision, upright posture, large brains, and -- most importantly -- language with syntax and that complex store of non-genetic information we call culture. However, in the last several centuries we've increasingly been using our relatively newly acquired power, especially our culturally evolved technologies, to deplete the natural capital of Earth -- in particular its deep, rich agricultural soils, its groundwater stored during ice ages, and its biodiversity -- as if there were no tomorrow.

The point, all too often ignored, is that this trend is being driven in large part by a combination of population growth and increasing per capita consumption, and it cannot be long continued without risking a collapse of our now-global civilization. Too many people -- and especially too many politicians and business executives -- are under the delusion that such a disastrous end to the modern human enterprise can be avoided by technological fixes that will allow the population and the economy to grow forever. But if we fail to bring population growth and over-consumption under control -- the number of people on Earth is expected to grow from 6.5 billion today to 9 billion by the second half of the 21st century -- then we will inhabit a planet where life becomes increasingly untenable because of two looming crises: global heating, and the degradation of the natural systems on which we all depend.

Our species' negative impact on our own life-support systems can be approximated by the equation I=PAT. In that equation, the size of the population (P) is multiplied by the average affluence or consumption per individual (A), and that in turn is multiplied by some measure of the technology (T) that services and drives the consumption. Thus commuting in automobiles powered by subsidized fossil fuels on proliferating freeways creates a much greater T factor than commuting on bikes using simple paths or working at home on a computer network. The product of P, A, and T is Impact (I), a rough estimate of how much humanity is degrading the ecosystem services it depends upon.

The equation is not rocket science. Two billion people, all else being equal, put more greenhouse gases into the atmosphere than one billion people. Two billion rich people disrupt the climate more than two billion poor people. Three hundred million Americans consume more petroleum than 1.3 billion Chinese. And driving an SUV is using a far more environmentally malign transportation technology than riding mass transit.

The technological dimensions of our predicament -- such as the need for alternatives to fossil fuel energy -- are frequently discussed if too little acted upon. Judging from media reports and the statements of politicians, environmental problems, to the degree they are recognized, can be solved by minor changes in technologies and recycling (T). Switching to ultra-light, fuel-efficient cars will obviously give some short-term advantage, but as population and consumption grow, they will pour still more carbon dioxide (and vaporized rubber) into the atmosphere and require more natural areas to be buried under concrete. More recycling will help, but many of our society's potentially most dangerous effluents (such as hormone-mimicking chemicals) cannot practically be recycled. There is no technological change we can make that will permit growth in either human numbers or material affluence to continue to expand. In the face of this, the neglect of the intertwined issues of population and consumption is stunning.

Many past human societies have collapsed under the weight of overpopulation and environmental neglect, but today the civilization in peril is global. The population factor in what appears to be a looming catastrophe is even greater than most people suppose. Each person added today to the population on average causes more damage to humanity's critical life-support systems than did the previous addition -- everything else being equal. The reason is simple: Homo sapiens became the dominant animal by being smart. Farmers didn't settle first on poor soils where water was scarce, but rather in rich river valleys. That's where most cities developed, where rich soils are now being paved over for roads and suburbs, and where water supplies are being polluted or overexploited.

As a result, to support additional people it is necessary to move to ever poorer lands, drill wells deeper, or tap increasingly remote sources to obtain water -- and then spend more energy to transport that water ever greater distances to farm fields, homes, and factories. Our distant ancestors could pick up nearly pure copper on Earth's surface when they started to use metals; now people must use vast amounts of energy to mine and smelt gigantic amounts of copper ore of ever poorer quality, some in concentrations of less than one percent. The same can be said for other important metals. And petroleum can no longer be found easily on or near the surface, but must be gleaned from wells drilled a mile or more deep, often in inaccessible localities, such as under continental shelves beneath the sea. All of the paving, drilling, fertilizer manufacturing, pumping, smelting, and transporting needed to provide for the consumption of burgeoning numbers of people produces greenhouse gases and thus tightens the connection between population and climate disruption.

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Paul and Anne Ehrlich are in the Department of Biology and the Center for Conservation Biology at Stanford University, where he is Bing Professor of Population Studies and Professor of Biological Sciences and she is Senior Research Associate. Their latest book, The Dominant Animal: Human Evolution and the Environment (Island Press), focuses on the issues cited in this article and includes references.

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