Earth, Wind, Water and Fire: Resource Exploitation in the Twentieth Century

J. R. McNeill is a professor in the history department at Georgetown University. His books include Something New under the Sun: An Environmental History of the Twentieth-Century World (Norton, 2000).

By the standards of the more distant past, the twentieth century was very peculiar. One measure of its peculiarity is its prodigality: its record of resource use. On several occasions, concerned observers lamented the rate of resource use and predicted dire shortages. The shortages predicted rarely occurred, normally because price signals provoked either conservation or more thorough efforts to locate further supplies (or both). Shortages that did occur usually proved less dire than expected, normally because of substitution of one material for another.

This is not to say that the environmental effects of human action in the twentieth century were inconsequential: far from it. Rather, it is to say that those effects proved, and are proving, more troublesome in departments other than those usually anticipated. The world in the twentieth century did not run short of coal, oil, natural gas, timber, nickel or uranium. It depleted its supply of all these things, but not seriously. It did not even run short of food, despite a 4-fold expansion in human numbers, although patterns of food distribution meant that famines still took place. No, the most serious overexploitation was that of sinks for wastes. That is because for many human uses there are no substitutes for air and water; and because the reigning conceptions in economics and law meant that the price mechanism did not provide useful signals. The second most serious overexploitation, paradoxically, was of renewable, biological resources.

The Magnitudes of Change

Let me begin with some rough estimates of the size and intensity of environmental changes, worldwide, in the twentieth century, and with estimates of the strength of the social and economic forces driving these changes.

Raw population growth was, in my opinion, the second most important driving force behind twentieth-century environmental change. Whereas throughout most of human history global population grew very slowly, by 1900–50 the rate attained nearly 1 per cent per year. And by the second half of the twentieth century, the rate climbed to 1.7 per cent per year, and indeed at times to over 4 per cent in a few countries. The global population growth rate peaked in the late 1960s, and has since been in decline, although total population continues to grow. Of all the years lived by hominids and Homo sapiens over the past four million years, about 20 per cent were lived in the twentieth century. The global population growth rates of the late twentieth century were about ten thousand times greater than those prevailing in pre-agricultural times—that is, for most of human history. Our times, it can hardly be emphasised enough, constitute an extreme departure from the patterns of the deeper past.

They also constitute a departure from the patterns of the future. While we cannot predict the demographic future with precision, we can be quite sure that growth rates of 1–2 per cent, the twentieth-century experience, will not last. Demographers predict steady declines in growth rates over the next fifty years. They may be wrong, but they will not be far wrong. If twentieth‑century growth rates were to persist, within a few centuries the earth would be encased in a mass of human flesh expanding outward with a radial velocity greater than the speed of light. We can rest assured twentieth-century growth rates will not long endure.

The world’s economy grew even faster than population in the twentieth century, which is why we are (on average) richer than our grandparents and great-grandparents. The size of the world’s economy has grown by about 130-fold since 1500, and about 15-fold since 1900.¹ Today Japan alone produces as much as the whole world did a century ago. All of us alive today have come to regard such a fantastic expansion of wealth as normal, as it has been throughout our lifetimes with only brief interruptions. But it is anything but normal by the standards of the more distant past. Much of this growth was driven by population, the rest by technological and organisational changes. On a per capita basis, average incomes grew 4-fold in the twentieth century. This is an average, which of course disguises gross inequities. The average Mozambican has an income well under half the global average of five hundred years ago and less than 2 per cent of the average German’s or American’s. The twentieth century saw a tremendous expansion in inequality as well as in the creation of wealth.

A big part of the reason that economic growth outstripped population growth lies in the history of energy use in the twentieth century. This I regard as the single most important driving force behind modern environmental change and resource use. The world’s total energy use grew by nearly 5-fold in the nineteenth century and then by another 13- or 14-fold in the twentieth century. The chief reason for this was the development of fossil fuels, mainly coal and oil, but since 1950, also natural gas. Nuclear energy and hydropower played much smaller roles. Around 1890, fossil fuels came to provide more than half of the world’s energy supply, so the twentieth century was truly an age of fossil fuels.

In the hundred centuries from the dawn of agriculture to 1900, humanity used only about two-thirds as much energy (most of it from biomass) as it used in the twentieth century. Indeed, it is likely that humankind used more energy in the twentieth century than in all preceding human history put together. From the point of view of energetics, the twentieth century was extremely peculiar.

The twentieth century was peculiar in many other respects directly relevant to resources and environment. The world’s total urban population grew by about 13-fold, and the proportion of people living in cities by nearly 4-fold. The world’s total industrial output grew by roughly 40‑fold, its freshwater use by 9-fold and its irrigated area by 5-fold. All this stood behind the incessant quest for more food, coal, oil, mineral ores, water and almost every other resource one can think of. The scope and scale of these changes, which occurred in a mere three or four human generations, will probably in the fullness of time come to seem the most important thing about the twentieth century.

Resource Stress and Shortage

Since at least 1789, not long after James Watt’s decisive improvement of the steam engine that made coal the central fuel of the Industrial Revolution, Englishmen were calculating how long their island’s coal supply might last. The early forecasts averaged around three hundred to four hundred years. In 1865 the English logician and economist William Stanley Jevons published a book called The Coal Question, by far the most careful of these efforts. He took stock of the escalating figures concerning coal consumption in Britain, consulted the estimates of how much coal remained in the ground, and concluded that a crisis of coal supply lay ahead. While he never said that Britain would run out of coal, he forecast that by 1950 or 1970 the price of recovering further coal would be so high that Britain’s prosperity would be a thing of the past. The work won Jevons wide renown and a chair in political economy.

But Jevons was mistaken. There was plenty of coal left underground in Britain. When the price of coal crept upward, as it did from time to time, British miners and geologists found coal in new places and engineers devised new machines that made it worthwhile to dig out more from old places. Eventually the miners and their employers convinced Parliament that coal was so essential that they extracted subsidies from the government, encouraging the quest for coal that would otherwise have been unrewarding to mine. Even today, billions of tons later, there is still plenty of coal in Britain. Most of it is probably destined never to be mined. And Britain is far more prosperous than in Jevons’s day, although it is no longer the richest country in the world. Britain’s coal industry is indeed in decline, but that is owing to a conjuncture of events in the 1980s: the rise of a British oil industry in the North Sea and the determination of Prime Minister Margaret Thatcher to rid British politics of the power of trades unions.

What was true of British coal was true of the world’s: the estimated supply of global coal reserves doubled between 1913 and 1990 despite the mining in the meantime of two hundred gigatons. Global coal reserves today stand at some three hundred years’ worth, based on the consumption rates of the 1990s. Some authorities estimate six hundred years’ worth of coal.² People keep finding more coal and devising cheaper ways to mine it.

In the early 1900s, when the United States was pioneering the conversion of both transport and industry to oil, worried observers undertook the same sort of calculation for American oil as Jevons had made for British coal. The first estimates implied only a ten-year supply. As late as 1930, given the best estimates of existing reserves and trends in oil use, it seemed the oil might run out by 1940. (If it had, the Second World War would have turned out differently.) But these predictions proved as inaccurate as Jevons’s and for the same reasons: oil was found in new places, and price rises and better drilling techniques made it possible to find more in the same old places.

In the United States, more oil was found in the 1930s than in any decade before or since. Prevailing estimates of potentially recoverable oil continued to grow, by 4 to 7-fold between 1940 and 1980. Most of us can remember that in the early 1970s, when political events brought about a quadrupling of crude-oil prices, dire predictions about oil supply followed. The US Central Intelligence Agency in 1978 estimated that global production would have to decline by 1988 at the latest because of shortages. But within ten years the proven reserves of oil had jumped to an all-time high: once again higher prices had made it rewarding to find, drill and pump up more oil. Indeed, since 1920 the ratio of oil reserves to annual production has remained between twenty-five and forty, that is, a twenty-five to forty-year supply (the same is true for natural gas, despite the sharp increase in consumption since 1960). The price mechanism, even in the regulated and subsidised fossil fuel markets, has to date produced a rough equilibrium. High prices provoke exploration and production, leading to oversupply and lower prices, in turn resulting in less exploration and production, which eventually leads to tighter supply and higher prices again.

Throughout the twentieth century this cycle has inspired inaccurate predictions for coal, for oil, for copper, for uranium (which in the 1970s was thought to exist in supplies sufficient to last only until 2000 or 2020 and is now expected to last another one hundred years) and sundry other raw materials. At the moment, the best estimates are that there is about forty-one years’ worth of oil left at current consumption rates. But these rates will probably fall as oil gets more expensive, which it will from time to time (and has been doing since 1999). Oil will still be in the ground a century hence. It is not, of course, that there is an infinite supply of these things on the earth: there is not. But we shall never dig out the last ton of coal or pump up the last barrel of oil, because long before we get to that point it will be economic to substitute other sources of energy. And, for that matter, if we did burn all that coal and oil, the carbon dioxide levels in the atmosphere would be several times higher than at present, and the globe probably as warm as at any time in the earth’s history. This leads to the heart of the matter.

But before we get there, I want to emphasise one thing. While I claim that there was no coal crisis or oil shortage on a global basis, this does not mean that everyone always has enough. In 1919–20, my grandparents passed a cold Toronto winter without coal because they did not have money to buy it, even though there were trillions of tons in the earth and billions in Canada. Every year many people die of hunger, but the world is not short of food. Overall supply and distribution are quite different matters.

The Overexploitation of Sinks

The atmosphere and hydrosphere are used as sinks for all manner of pollutants. So are soils. Air, water and earth all have the capacity to absorb, break down or recycle certain amounts of certain pollutants. But there are thresholds beyond which pollutants accumulate faster than they can be dissipated. In the twentieth century the atmosphere and hydrosphere were obliged to accept overloads. As a consequence they became durably polluted—in places acutely so—with unwelcome consequences for living things in general and human health in particular. These are the most important overexploitations of resources in the twentieth century. Happily, they are also among the most reversible—technically at least. Actually reversing such trends requires political coalitions that are difficult to create.

Air pollution, most of which came from the combustion of fossil fuels, increased—very roughly speaking—by 2 to 10-fold in the twentieth century. Ecosystems were affected most by acidic emissions, mainly of sulphur dioxide, but also from nitrogen flux. In the long run, they may be yet more affected by carbon emissions via global warming, but that belongs to the future.

The most important air pollution problem for human health was the prevalence of particulate matter in urban areas and indoors. Sulphur dioxide and lead emissions also produced health problems. In the 1990s, urban air pollution killed about half a million people annually, a bit fewer than auto accidents, and a quarter of the toll from malaria or tuberculosis. All told, urban air pollution probably killed somewhere around twenty-five to forty million people in the twentieth century, numerically about equal to the great influenza pandemic of 1918–19 or the combined casualties of the two world wars; equal to, but not equivalent to, because the death toll from air pollution came over a century, rather than in a few years, and because the respiratory ailments caused by air pollution tended to kill the very old, the very young and those already sick, whereas war and influenza killed far more people in the prime of life.

Indoor air pollution, mainly in poor countries where fuel wood and coal are used in domestic heating and cooking stoves, surely killed far more people. I have found no reliable data and will make no estimates. In any case, this is not a matter of overexploitation of resources, unless one considers indoor air as a resource.

The overexploitation of water as a sink for wastes was more important still. The rub came with fresh water because salt water (which accounts for 97 per cent of the earth’s water) is no use for most human purposes. Most fresh water is deep underground or locked up in ice sheets. Getting the right amounts of fresh water in the right places (cities, fields) at the right times has always posed a challenge to societies. Those that have answered it successfully enjoyed (and enjoy) great advantages in health and productivity over those that have not. At times, freshwater supply served as the key constraint on population and economic growth.

Pollution of fresh water aggravated these problems. For thousands of years people have dumped wastes in the nearest stream or river. Most of these were biological wastes. In the nineteenth and twentieth centuries, with the emergence of chemical and fertiliser industries, people started dumping large quantities of chemical wastes as well, occasionally obliterating all life in some bodies of water. From the viewpoint of human health, however, biological contamination in the form of pathogenic microbes remained by far the most important water problem. Today, water pollution kills about five million (some estimates say ten million) people per year, some ten times the toll from outdoor air pollution. Most of these fatalities are in poor countries where sanitation infrastructure is weak. A very rough guess of the twentieth century’s death toll from polluted water is three hundred to five hundred million. Most of these were and are small children, but dysenteries, typhoid and cholera also killed plenty of people in their most productive years. This in itself is a good argument for the proposition that the most serious overexploitation of resources in the twentieth century was of freshwater sinks.

Pollution Control

An encouraging feature of the twentieth century was its attention to the problems created by overuse of sinks. For centuries, people had sought to segregate waste water from drinking water, but only rarely with consistent success. With the emerging science of bacteriology in the late nineteenth century, it became possible to take effective action, to convince relevant political bodies of that possibility, and to improve the health of hundreds of millions. The decisive steps—wastewater treatment, large-scale metropolitan waterworks—occurred between 1890 and 1930 in most of the rich countries and in some colonial settings.³ In poorer countries this “sanitation revolution” took place only after 1950 and is by no means complete today.

Lowering the actual pollution loads of the world’s waters was a different matter from safeguarding the supplies of drinking water. Efforts in this direction became increasingly common in the nineteenth century, at least in Britain where rivers were dangerously polluted. But the most effective measures came only after 1970 as part of the worldwide ecology movement. At very modest cost it proved possible to reduce drastically the pollution loads from factories and city sewage systems, although not from farms. The modern history of the Rhine river is a prominent example of how quickly waterways—at least rivers—can be cleaned up, to the point where fish species long absent will return.⁴ Lakes, which retain their water for years (rivers keep a given drop only for weeks), proved much harder to clean up, but several modest successes occurred, as in the North American Great Lakes.

Such successes, it must be remembered, were more common in prosperous lands—Japan, Western Europe, North America—than elsewhere. The pollution loads of the Yangtse, Ganges, Volga and Nile continued to mount throughout the twentieth century, ruining fisheries and the health of many of those who needed these rivers’ waters to drink. By 2000, among the dozens of major rivers in Latin America, Africa and Asia, only two featured ecosystems undamaged by pollution: the Amazon and the Congo, which carry so much water that they can dilute the modest volumes of pollution they must absorb.⁵

The ambition to control air pollution also long predates the twentieth century. Some London regulations go back to the thirteenth century. But effective, intentional reductions in urban air pollution date only from the mid-twentieth century. St Louis was a pioneer in this respect, creating an unlikely coalition of politicians, businessmen, crusading journalists and irate housewives in 1940–1 that sharply reduced smoke, soot and sulphur emissions from the coal‑powered city. Pittsburgh, London, Osaka—a threesome of heavy air polluters—managed sharp reductions in their emissions between 1955 and 1970. They achieved it through fuel substitutions, using less coal and more natural gas, through various technical improvements to smokestacks and auto engines, and various regulations. The resulting improvements in air quality and human health were correspondingly sharp in these and other coal-fired cities of Europe, North America and Japan.

Similar achievements marked the late twentieth-century history of a few cities outside the rich countries. Ankara, which uses a lot of heating fuel in winter, switched from Turkish lignite (an especially dirty fuel) to Siberian natural gas in the early 1990s, sharply improving its urban air quality. Mexico City struggled with its gargantuan air pollution problems, by some reckonings the worst in the world. Mexico City suffers from the exhausts of a huge vehicle fleet as well as the emissions from tens of thousands of industries, a legacy of the centralisation of the Mexican Revolution (1910–20). These modern problems were rendered more acute because of the city’s location, in a bowl surrounded by mountains, which allows for frequent temperature inversions that trap pollution. (When the Aztecs chose it for their capital in 1415 they had other considerations in mind than air pollution.) By the 1980s air pollution in Mexico City reached such heights that, on one occasion at least, it killed birds in flight. But in the course of the 1990s, local and national authorities recorded some successes, lowering concentrations of some pollutants and stabilising others. The United Nations recognised Mexico City more than once as a leader in efforts against urban air pollution.

Meanwhile, however, many large cities at the end of the century suffered from increased, rather than decreased, pollution loads and for whatever reasons did not focus on air quality in the way that Mexico City did. In Delhi, Bangkok, Cairo and Seoul, burgeoning vehicle use and/or reliance on coal combined to make for particularly unhealthy air. In several cities of north China, heavy reliance on a particularly dirty coal created what are probably the most polluted cities on the earth today. Urban air quality, which a hundred years ago was much worse in the rich countries than in the poor ones, is today among the many reasons life is easier in the rich world.

On a global basis, the whole atmosphere was seriously overexploited as a sink in the twentieth century. This was especially true for two classes of pollutants: ozone-rupturing chemicals such as CFCs, and greenhouse gases. These stories are very familiar by now and I shall not rehearse them. I will only say that the consequences of depleting stratospheric ozone and of loading the atmosphere with greenhouse gases are durable across several human generations, widespread around the world and potentially acute. The full range of consequences is not yet apparent, but it seems quite possible that they will one day appear as the principal costs of overexploitation of the atmospheric sink. We should know definitively in a century or less, which inconveniently will be far too late to do anything about it.

Renewable Resources

It is one of the ironies of environmental history—a field rich with ironies—that several so-called renewable resources came under greater stress in the twentieth century than non-renewables such as coal and copper. For example, fisheries and forests: as biological resources these are renewable. But in the twentieth century the global marine fish catch climbed from about two million metric tons to about seventy-five million (not counting the inland fish catch or aquaculture). If official figures are at all accurate, the seas surrendered more fish in the twentieth century than in all previous centuries combined. As a result of intensifying fishing efforts and the lack of effective regulation, one marine fishery after another collapsed in the twentieth century.

The greatest collapse came in 1972 in the world’s richest fishery, the anchoveta and jack mackerel grounds off the Peruvian coast. Between 1967 and 1971, Peru’s fisheries accounted for a fifth of the world’s total. But beginning in 1972, the catch fell off by 60–85 per cent, with the absolute nadir coming in 1982–3. The costs to Peru’s economy and society were considerable. Since 1983 the fishery has recovered somewhat, but harvests have yet to return to the levels of the 1960s. The Peruvians were more fortunate than some. The California sardine fishery, a mainstay of the central Californian coast in the early twentieth century, collapsed after 1945 and disappeared entirely in 1968.

Some fisheries recovered, some did not, but the total catch continued to climb as new fisheries were discovered and old ones subjected to more efficient methods. The last frontier was the pilchard fishery of the southeast Pacific, opened up in 1971. There are no significant new fisheries left to tap. Since the late 1980s, all marine fisheries have been exploited at or above sustainable levels. To maintain the catch at more or less the same levels, increasingly uneconomic fish are targeted, destined for market as fish meal for use as fertiliser. About a billion people depend on marine fish as their chief source of protein, most of whom have had to pay more for it recently. Beyond overfishing’s consequences for humans, marine ecosystems, especially those of coastal waters, underwent dramatic reorganisation as fishing eliminated top predators such as tuna or cod.⁶

Efforts to regulate fisheries so as to prevent overfishing made only modest progress. Fishermen normally have every incentive to get to the fish before their competitors do. Any restraint is wasted if it merely allows another fisherman to catch more fish. The most promising efforts were pioneered in the 1980s by New Zealand and subsequently imitated by about fifteen other countries. New Zealand’s system essentially privatised fisheries, giving fishermen tradeable quotas for specific fish in specific areas. This altered the fishermen’s incentive structure and reduced overfishing, allowing stocks to survive and generate sustainable harvests. But making the same scheme work in international waters, without the oversight that the New Zealand government could provide, proved much more challenging.

The history of the world’s forests in the twentieth century is another case, somewhat less acute but perhaps more consequential, of overexploitation of a renewable resource. Forest and woodland area shrank by about 20 per cent in the twentieth century, accounting for perhaps half of the net deforestation in world history over the last ten thousand years. Of the twentieth century’s total deforestation, about half occurred in the tropics after 1960, mainly in South-East Asia, West Africa, Amazonia and Central America. People clear forests in order to use the timber or to use the land (or, rarely, both). Over the course of the twentieth century, about 80 per cent of forest clearance was motivated by the wish to farm the land, about 20 per cent by the quest for timber.

The temperate and boreal forests of the world had a different history. They were much reduced in prior centuries, but by 1910 or 1940 their extent stabilised and in many places began slowly to grow. In Western Europe, forest area grew throughout the twentieth century, as it did in the United States from about 1930 onward. The deforestation in the tropics was so rapid, however, that the net global effect was to make the twentieth century by far the worst in this respect in world history. As of 2000, the world retained three large blocks of forests, one in northern North America, one in northern Europe and Siberia, and a third, shrinking fast, in the Orinoco and Amazon basins of South America.

The full consequences of this massive forest clearance, one of the hallmarks of the twentieth century, are unclear. Surely it reduced biodiversity somewhat, although measurement remains elusive here. Surely it also added plenty of carbon to the atmosphere, perhaps 10–20 per cent as much as fossil fuel combustion did. Surely it changed local climates and exposed millions of hectares of soil to erosion. It also added to the world’s cropland, which doubled in the twentieth century, making it possible to feed more people than ever before. It will take time and much work to figure out what the full meaning of this modern history of forest clearance might be.

Awaiting History’s Verdict

While I remain persuaded that the most important overexploitations of resources in the twentieth century were those of the atmosphere and of fresh waters as sinks for wastes, this can only be a provisional judgement. Biological resources were also overexploited in the sense that their stocks declined, and in the case of fisheries in the further sense that their yields diminished, sometimes to zero. A collapse of biodiversity on the scale of the five prior extinction spasms in the earth’s history—a catastrophe that some ecologists have lately begun to predict—would alter this perspective.

It is in fact too soon to tell just which overexploitations will ultimately prove the most significant. Fish populations sometimes bounce back in a year or two from severe declines. The California sardine population might make a miraculous recovery in a few years. Aquaculture might eventually allow all oceanic fisheries to recover (at present about 15 per cent of the marine “catch” comes from farmed fish). Forests usually can recover in a century or three, depending on conditions. Some probably can never recover. The stratospheric ozone shield will return to its former robust state by 2080 or so, if emissions of ozone-rupturing chemicals are checked, as to a considerable degree they have been since the Montreal Protocol of 1987. Cheap desalinisation of seawater would at a stroke reduce the costs of freshwater pollution. And the future history of global warming will determine how seriously one ought to regard the twentieth century’s (and the twenty-first’s) loading of the atmosphere with greenhouse gases. The end of history is nowhere in sight.

Endnotes

1. These approximate figures are based on the work of Angus Maddison, Monitoring the World Economy, 1820–1992 (Paris: OECD Development Centre, 1995).

2. See, for example, K. S. Deffeyes, Hubbert’s Peak: The Impending World Oil Crisis (Princeton, N.J.: Princeton University Press, 2001), and Vaclav Smil, Energies (Cambridge: MIT Press, 2000).

3. For the US story, see Martin Melosi, The Sanitary City (Baltimore: Johns Hopkins University Press, 2000).

4. See Mark Cioc, The Rhine: An Ecobiography (Seattle: University of Washington Press, forthcoming).

5. World Commission on Water, cited in Marq de Villiers, Water: The Fate of Our Most Precious Resource (Boston: Houghton Mifflin, 2000), p. 88.

6. See Jeremy B. C. Jackson et al., “Historical Overfishing and the Recent Collapse of Coastal Ecosystems”, Science 293 (2001), pp. 629–38.