Perceiving the Population Bomb: The real damage began about 60 years ago.

Thirty-two years ago, in 1968, Paul Ehrlich sounded a wake-up call to the world with his book The Population Bomb. Now that we can see the Bomb in historical perspective, even establishing when it went off, let us set ourselves the task of perceiving--with rigorous objectivity--the explosion of the Bomb and the collateral damage it has caused.

It was only in the 199Os that many demographers came to realize that Ehrlich's message was essentially correct. Writing in 1991, Clive Pointing started the preface of his great book, A Green History of the World, with these words: "As some people climb mountains because they are there, others find themselves writing books because they are not there." His book was indeed ground-breaking; before it was published, few people can have had an adequate grasp of humanity's impact on the environment. Two years later, in 1993 the biophysical scientist, Vaclav Smil, wrote: "We have at least started to realize the enormity of environmental transformation which is imperiling the survival of modern civilization." Smil identified a spectrum of critical changes taking place in the Earth's condition, and noted that "these changes can be ordered into three broad categories: declining availability of critical natural resources and services; changing composition of the atmosphere; and the loss of biodiversity." [Italics added.] It may be impossible to rank those three in importance. However, we can use the "changing composition of the atmosphere" to establish when the Bomb went off, so let us look at that first.

In 1990, the world was emitting, from the burning of fossil fuels and cement production, about 4.2 tons of carbon dioxide per person, indicating an energy use of about 64 GJ (gigajoules) per person per year. Sixty-four GJ/capita, as well as being the average use of energy in 1990, is a reasonable lower limit for average energy use. Vaclav Smil provides the evidence. He shows us graphically that infant mortality drops precipitously as per capita energy use rises to 50 GJ per year. Thereafter, further improvement becomes more gradual. Of course there is no clear changeover point, but 64 gigajoules a year per person seems a judicious minimum. In any case, should you want to argue for a lower average use of energy than 64 GJ/year, then you will need to argue for accepting an infant mortality higher than 15 per 1000 births. Countries like Greece, Japan, and the United Kingdom, which have better infant mortality rates than that, also have energy use above 64 GJ/capita/year. Of course a correlation does not prove a causative relationship, but Smil also shows that good access to post-secondary education (20 percent of eligible population) generally involves per capita energy use above 70 GJ/year. It does seem inherently likely, moreover, that a certain minimum energy availability is necessary to achieve these benchmarks.

Assuming there is some minimum per capita emission figure, then, just how much carbon dioxide can the Earth tolerate? In order to stabilize the amount of carbon dioxide in the atmosphere, the Intergovernmental Panel on Climate Change has estimated that carbon dioxide emissions from fossil fuel would have to be reduced by at least 60 percent from their 1990 level of 22.3 billion tons, which would yield an upper limit of 8.9 billion tons. Thus the maximum population which the Earth can accommodate, while allowing the aforesaid carbon dioxide emission of 4.2 tons per person per year, is 8.9/4.2=2.1 billion people. World population reached 2.1 billion in 1940, so 1940 is the time that the Bomb went off. Collateral damage has been steadily accruing ever since, in the form of atmospheric disturbance with its corollaries, such as melting glaciers, droughts, floods and increasing frequency of the El Nino phenomenon.

By the 1990s, the tide of humanity had swept across the globe appropriating to its own use the most productive ecosystems (see map, inside back cover). By then, Smil tells us, there was only about one-third of the continental surface left over for the use of other life forms. Of this remnant, he says, "most of this area is in highly stressed low-productivity eco-systems. About 40 percent of the total are in circumpolar tundra communities, and another 20 percent are in subtropical deserts and semi-deserts, while only about 6 percent of the remaining wilderness during the mid-1980s was in tropical rain forests, and less than 2 percent in temperate (rain and broadleaf) forests." Thus we have not been generous to other species and, as Smil observes, "There is general agreement among the students of conservation biology that most existing national parks and reserves are far too small to guarantee long-term survival of especially large species."

Of course not all the damage occurred since the Bomb went off, but since the world has acquired two thirds of its human population since that time, it is likely that most of it did. Moreover, since the rate of damage has doubtless been accelerating, there is plausibility in the thesis that the human race is likely to cause an extirpation of species comparable to that of the previous five mass extinction events. Such, then, is our perception of collateral damage with respect to Smil's category "loss of biodiversity."

The remaining category mentioned by Smil is "declining availability of critical natural resources and services." For assessing that, let us turn first to Colin Campbell, who estimates that the world, currently using about four cubic kilometers of crude oil a year, has used about half of its conventional oil and close to half of its natural gas. Moreover, we learn from Richard Duncan that both oil supply per capita and energy supply per capita peaked in 1979. But for most of the details of collateral damage in this category, it would be best to turn to a 1999 paper by David Pimentel et al. Incidentally, this paper also proposes the need to aim for a world population of 2 billion, although for different reasons from carbon dioxide emissions. From it, we can add the following items to our list (all thoroughly referenced in the original): (a) "3 billion humans malnourished world wide" (b) "40,000 children die each day due to malnutrition and other diseases"; (c) "Globally, the annual loss of land to urbanization and highway ranges from 10 to 35 million hectares per year, with half of this lost land coming from cropland"; (d) "Worldwide, more than 10 million hectares of productive arable land are severely degraded and abandoned each year" (about 7 percent of the total in a decade); (e) "Water demands already far exceed supplies in nearly 80 nations of the world"; (f) Since 1960, "nearly one-third of the world's arable land has been lost due to urbanization, highways, soil erosion, salinization, and water logging of the soil"; (g) "grain production per capita started declining in 1984 and continues to decline"; (h) "irrigation per capita started to declining in 1978 and continues to fall"; (i) "food production per capita started declining in 1980 and continues to fall"; (j) "fertilizer supplies essential for food production started declining in 1989 and continue to do so." That abbreviated shortlist, which omits loss of soil -- serious but difficult to measure -- suffices to indicate the importance of the last of Smil' s three categories, "declining availability of critical natural resources and services." However, perhaps we should also recall the net loss of forest, equal to an area of at least 12 million hectares (130 miles by 130 miles) per year. We can, for the same reasons as previously, deduce that most of the damage has happened since the Bomb went off in 1940.

So, that concludes our attempt to perceive the Population Bomb. Let us now leave the hard "facts," and muse on more speculative matters. Because the Bomb exploded some 30 years before Ehrlich's book, we might be inclined to blame him and his fellow ecologists for not sounding the wake-up call earlier. However were they to have done so, the message would have fallen on deaf ears. Even some of the most intelligent people could not see that there was a population problem, and some were unwilling even to concede that a problem loomed over the horizon. And today there are few ready to listen to those who have, for several decades, been toiling to awaken the world to our perilous situation.

The efforts of some people have been superlative. In addition to the work of Paul and Anne Ehrlich, Clive Ponting, Colin Campbell, and David and Marcia Pimentel, we have had important contributions from Virginia Abernethy, Albert Bartlett, Lester Brown, Sandra Bukkens, Gretchen Daily, Richard Duncan, Robert Engleman, Garrett Hardin, Mario Giampietro, Norman Myers, Jack Parsons, Peter Tod, Mary White, and Walter Youngquist. Although it is hard to say whether the course of history has been influenced by the many fine lectures these people have given (1,200 from Al Bartlett alone), and the equally superb papers and books they have written, the fact that homo sapiens has produced such farsighted individuals--striving to abate our deep-dyed procreational proclivity -- gives some cause for admiration of the human race, whatever one may think of the chances of the species surviving its incompetence in matters of fertility.

Andrew R.B. Ferguson is research co-ordinator at Optimum Population Trust in the United Kingdom.