Weighing Relative Burdens on the Planet


by Paul Ehrlich

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Concern about population problems among citizens of rich countries generally focuses on rapid population growth in most poor nations. But the impact of humanity on Earth's life support systems is not just determined by the number of people alive on the planet. It also depends on how those people behave. When this is considered, an entirely different picture emerges: the main population problem is in wealthy countries. There are, in fact, too many rich people.

The amount of resources each person consumes, and the damage done by the technologies used to supply them, need to be taken as much into account as the size of the population. In theory, the three factors should be multiplied together to obtain an accurate measurement of the impact on the planet*. Unhappily, Governments do not keep statistics that allow the consumption and technology factors to be readily measured—so scientists substitute per capita energy consumption to give a measure of the effect each person has on the environment.

USING AND CONSUMING This makes sense. All human activities require the use of energy, and the most environmentally destructive of those activities for the most part require a great deal of it. Human beings use energy to obtain resources, process them into useful items, and then use or consume them. At every step, environmental damage is done.

In traditional societies—more or less in balance with their environments —that damage may be self-repairing. Wood cut for fires or structures regrows, soaking up the carbon dioxide produced when it was burned. Water extracted from streams is replaced by rainfall. Soils in fields are regenerated with the help of crop residues and animal manures. Wastes are broken down and reconverted into nutrients by the decomposer organisms of natural ecosystems.

At the other end of the spectrum, paving over fields and forests with concrete and asphalt, mining the coal and iron necessary for steel production with all its associated land degradation, and building and operating automobiles, trains and aeroplanes that spew pollutants into the atmosphere, are all energy-intensive processes. So are drilling for and transporting oil and gas, producing plastics, manufacturing chemicals (from DDT and synthetic nitrogen fertilizers to chlorofluorocarbons and laundry detergents) and building power plants and dams. Industrialized agriculture uses enormous amounts of energy—for ploughing, planting, fertilizing and controlling weeds and insect pests and for harvesting, processing, shipping, packing, storing and selling foods. So does industrialized forestry for timber and paper production.

PAYING THE PRICE Incidents such as Chernobyl and oil spills are among the environmental prices paid for mobilizing commercial energy—and soil erosion, desertification, acid rain, global warming, destruction of the ozone layer and the toxification of the entire planet are among the costs of using it.

In all, humanity's high-energy activities amount to a large-scale attack on the integrity of Earth's ecosystems and the critical services they provide. These include control of the mix of gases in the atmosphere (and thus of the climate); running of the hydrologic cycle which brings us dependable flows of fresh water; generation and maintenance of fertile soils; disposal of wastes; recycling of the nutrients essential to agriculture and forestry; control of the vast majority of potential crop pests; pollination of many crops; provision of food from the sea; and maintenance of a vast genetic library from which humanity has already withdrawn the very basis of civilization in the form of crops and domestic animals.

THE RELATIVE IMPACT The average rich-nation citizen used 7.4 kilowatts (kW) of energy in 1990—a continuous flow of energy equivalent to that powering 74 100-watt lightbulbs. The average citizen of a poor nation, by contrast, used only 1 kW. There were 1.2 billion people in the rich nations, so their total environmental impact, as measured by energy use, was 1.2 billion x 7.4 kW, or 8.9 terawatts (TW)—8.9 trillion watts. Some 4.1 billion people lived in poor nations in 1990, hence their total impact (at 1 kW a head) was 4.1 TW.

The relatively small population of rich people therefore accounts for roughly two-thirds of global environmental destruction, as measured by energy use. From this perspective, the most important population problem is overpopulation in the industrialized nations.

The United States poses the most serious threat of all to human life support systems. It has a gigantic population, the third largest on Earth, more than a quarter of a billion people. Americans are superconsumers, and use inefficient technologies to feed their appetites. Each, on average, uses 11 kW of energy, twice as much as the average Japanese, more than three times as much as the average Spaniard, and over 100 times as much as an average Bangladeshi. Clearly, achieving an average family size of 1.5 children in the United States (which would still be larger than the 1.3 child average in Spain) would benefit the world much more than a similar success in Bangladesh.

CLOSING THE GAP Professor John P. Holdren of the University of California has generated an "optimistic" scenario for solving the population- resource-environment predicament. This envisages population growth halted at 10 billion a century from now, and rich nations reducing their energy consumption to 3 kW a head. His population target is feasible with modest effort, and the reduction in energy consumption could be achieved with technologies already in hand—given the necessary political will—and would produce an increase in the quality of life. This would provide room for needed economic growth in poor nations, which could triple their per-person energy use to 3 kW. Thus the gap between rich and poor nations would be closed, while the total world impact would increase from 13 TW to 30 TW (10 billion x 3 kW).

Will the environment a century hence be able to support 2.3 times as much activity as today? It's questionable, but perhaps with care it could, at least temporarily. Success would require a degree of cooperation, care for our fellow human beings, and respect for the environment that are nowhere evident now. But society has shown it can change rapidly when the time is ripe; let us hope that the United Nations International Conference on Population and Development will help ripen the time.

* * *

* The relationship is summarized in the classic I=PAT identity: Impact is equal to Population size, multiplied by per capita consumption (Affluence), in turn multiplied by a measure of the damage done by the Technologies chosen to supply each unit of consumption.

Mr. Paul R. Ehrlich is Bing Professor of Population Studies and Professor of Biological Sciences at Stanford University in the United States. His most recent books, both co-authored with his wife Anne, are "The Population Explosion" (Simon and Schuster, 1990) and "Healing the Planet" (Addison-Wesley, 1991). The feature originally appeared in Vol. 6, No.3, 1994 of "Our Planet". The views expressed herein do not necessarily reflect those of UNEP.

UNEP Feature 1994/8

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