J.R. McNeill
Georgetown University

As a species, we’ve enjoyed a run of luck in the Holocene. In the last 10,000 years, while migration as a response to adversity has become progressively less viable, warming and cooling trends, and attendant sea level fluctuations, were small. Even the Little Ice Age, c. 1300-1850, amounted to a cooling (in Europe, where the data are best) of about half of one degree Celsius.

It made harvest failures more frequent in northern Europe, and probably contributed to the extinction of the tiny Greenland Norse settlement in the early 15th century. In lower latitudes the Little Ice Age probably featured desiccation and more frequent droughts, a much more disruptive experience than mild cooling or warming. But as nature’s surprises go, the climate change of the Little Ice Age was modest.2

In the past, nature’s shocks and stresses challenged all societies. In recent millennia, the most dangerous of these included epidemics, droughts, floods, earthquakes, and volcanic eruptions. Warming, cooling, and sea level changes were far down the list. Broadly speaking, these challenges came in two varieties: short, sharp shocks with durations of days, weeks or a year or two; and long, slow stresses that played out over decades or centuries, and were often invisible to people at the time.

In terms of demographic losses, epidemics were by far the most serious.3 Table 1 ranks the demographic seriousness of nature’s shocks in very rough terms. The mortality figures, given only as an order of magnitude, represent the maximum, meaning 95-99% of such incidents would kill fewer people. So for example, while there may have been a flood or even ten that has killed more than a million people, this represents the worst that floods have ever done to humankind.

The worst epidemics have killed 30-100 million people, even if one counts the bubonic plague pandemic of the 14th century as a single epidemic. The most recent epidemic on such a scale, the 1918-19 influenza, killed perhaps 40 million (about 2% of the global population). The ongoing AIDS pandemic has so far killed 25-30 million, about 0.5% of the current population.4

Such pandemics are mercifully rare, the outer edge of the misfortunes our species has suffered to date, but epidemics that affected regions or single cities were not, and they routinely killed 5-10%, or even more, of the affected population. Droughts at their worst killed a few million.

The long history of drought is notably fuzzy, and whether or not deaths ought to be laid at drought’s door is often unclear, especially for the deeper past. In the twentieth century, where the uncertainties are smaller, the most deadly droughts occurred in China in 1928-31, 1936, and 1941, with 2-5 million deaths on each occasion, generally through starvation. The famous Sahelian droughts of 1967-73 and again in the early 1980s, killed about a million people. In all probability some of the Indian famines of the 19th century killed more, but the figures are in dispute. 5

Floods too could kill thousands, even millions, although flood control and evacuation procedures have made a large difference in flood mortality. Since 1953, the annual average of deaths in floods in India, the country most afflicted by floods, is about 1,500. The worst flood in recent Chinese history, on the Yangzi in 1954, killed 30,000 people.

Yangzi floods of 1931, perhaps the most costly ever, killed 1-4 million, and those on the Hwang He in 1887 perhaps 1-2 million. The great North Sea floods of December 1953 killed some 2,400 in the Netherlands, whereas earlier floods, in 1212, had killed 60,000.

A 1342 flood in central Europe, which caused half of all the soil erosion over German lands in the past millennium, probably drowned hundreds of thousands of people.6 The greatest flood in US history, along the lower Mississippi River in 1927, killed 243.7

Of the many thousands of deadly earthquakes, only ten have killed more than 100,000 people. The worst occurred in China in 1566, killing perhaps 800,000. The Asian tsunami of December 2004, created by an earthquake, killed 284,000, while the 2005 earthquake in Pakistan killed about 79,000. The worst in U.S. history, San Francisco 1906, killed about 3,000.8

Of the countless volcanic eruptions, only six are likely to have killed more than 10,000 people. The worst came in 1815 (Tambora, Indonesia) and took 92,000 lives; Krakatau (1882) cost 36,000. The famous eruption of Mt Vesuvius in AD 79 killed about 3,600, while the worst in U.S. history, Mt. St. Helens in 1980, killed 57.

With the exception of the richer parts of the world since 1919, every generation everywhere lived with the likelihood of devastatingly lethal epidemic, flood, drought, and other sorts of natural risks.9

As a result, all societies had to build resilience to nature’s shocks. They did not, by and large, intentionally build resilience or resistant to nature’s slow-acting stresses, such as desiccation or soil salinisation, because these progressed too slowly to cause alarm, and normally too slowly to be noticed from one generation to the next.

But resistance and resilience to the easily observable short, sharp shocks was, always and everywhere, an important priority. Resistance and resilience are not the same thing. Resistance to flood, for example, can take the form of the construction of seawalls and dikes, as the Dutch have done for 600 years to keep the North Sea at bay. Resilience to flood means the capacity to recover as quickly and easily as possible, which might take the form of leaving a river floodplain uninhabited, used only for seasonal pasture, as was done along the Rhine until its canalisation (which began in 1815).

Societies built resistance to nature’s shocks as a conscious enterprise. In regions of the world prone to drought, they developed water-storage infrastructure such as cisterns. In flood-prone regions, they built homes on stilts. Cities developed quarantine routines to try to prevent epidemics. By the 19th century, the richer societies undertook to control river floods with dikes, dams, and canalisation.10

By the 18th century the Chinese Qing dynasty had constructed an elaborate system of state granaries intended to prevent famine from whatever cause (the Aztecs had done this on a smaller scale in the 15th century). Since the 1880s, public health services have made major efforts – by and large crowned by success – to prevent epidemics through sanitation reforms and vaccination regimes. Otherwise there would not be 6.6 billion people today.

There have always been limits to the degree to which resistance can be built. Preventing volcanic eruptions remains impossible and stopping lava flows implausibly expensive. Flood control is feasible, but only within limits, which occasionally are overtopped, as in the Mississippi basin in 1927 and 1993. Moreover, as the Mississippi floods show, societal faith in the infrastructure of resistance can undermine resilience: the opportunity cost of leaving a floodplain unoccupied seems excessive if one trusts the levees and dikes.

Resilience, on the other hand, has to date proved in abundant supply: our species has survived countless shocks and now covers the globe as never before. In our earliest years, as noted above, resilience consisted mainly of mobility, the ability to escape the worst of a natural shock through migration, and to start afresh in a new landscape. This remained an option until recent decades for millions of pastoralists and the few remaining hunting/foraging populations.

As recently as 1912-15, when severe droughts affected the West African Sahel, millions of people adapted by migrating southward, a feasible response because in those days West Africa had about one-eighth the population it carries today, and there were no effective border control regimes to inhibit migration.

For the great majority of our historical experience, mobility was the solution, the only necessary form of resilience, to nature’s shocks. Today it is severely restricted.

A second source of resilience in times past was simplicity combined with fertility. Societies with minimal infrastructure lose little except people in experiencing natural disasters, and new people are easily created. Rebuilding a city in the aftermath of flood or earthquake requires much more in the way of knowledge, investment, coordination, and cooperation, than does rebuilding a patchwork of fields and villages.

Most peasant societies prior to the 20th century maintained a stock of unmarried young people who, in the wake of deadly catastrophe, would stampede into marriage and within a year sharply raise birth rates. This was not a conscious strategy, but a result of custom and economic preferences. Nonetheless it provided resilience in the form of the ability to ramp up fertility quickly and jump start demographic recovery.11

For many centuries societies have also created more conscious mechanisms to improve resilience. Storing food in state warehouses to cope with dearth or famine is a practice intermittently practiced since ancient times, and brought to a high level of reliability by the Qing Dynasty in 18th century China.12 Transportation infrastructure, although built for other reasons, also provided resilience both in that it allowed faster evacuations from affected zones, and in that it allowed quicker rescue and relief. Societies with extensive and dense road and/or canal networks, for example, eliminated famine by the end of the 18th century, while those without remained vulnerable.

Organised relief efforts also improved resilience in modern history. The practice of maintaining contingency funds against disasters is probably nearly as old as money and treasuries. Providing government funds internationally for disaster victims dates back at least to a great Jamaican hurricane of 1783 and a Venezuelan earthquake of 1812. Standing international bodies devoted to disaster relief probably began no earlier than 1863, with the founding of the Red Cross (which until the late 1940s concerned itself almost entirely with victims of war, rather than nature’s shocks).13 The total effect upon societal resilience of such efforts and organisations has to date been modest, but they have eased the suffering of millions.

In general, the ability to withstand and recover from nature’s shocks has rested on mobility, simplicity of social structures and infrastructures, and on fertility. In the last two or three centuries, as societies have grown less simple, as fertility has fallen, and as mobility has become less feasible as a societal response, resistance and resilience have come to take more bureaucratic and technological forms, e.g. granaries, seawalls, and international relief organisations.

Since 1950 or so, the ability to evacuate millions and to bring large quantities of food and other supplies, quickly and over great distances, has improved immensely. As a result modern famines have mainly been an artifact of war and totalitarian politics, rather than environmental factors.14 Ironically, the logistical capacity to do such things was in large part developed to meet the military requirements of global total war, especially in World War II.
As a happy consequence, disease, droughts, floods, and earthquakes that a century or more ago might have killed millions more recently would only kill thousands. This extraordinary ability to mitigate disaster has hinged on the comparative stability of international politics since 1945, which, while those of us who lived through these decades tend to regard them as turbulent, in comparison to earlier times provided an opportunity for what we might call regimes of resilience to develop.

Such regimes operated in times of rapid population growth (and hence quick demographic recovery), which may in and of itself eventually reduce or undermine their effectiveness: resilience in the face of drought or similar shock can be harder to maintain in more crowded circumstances, as can resistance to disease.

Vulnerability to shock consisted of several components. First and most obviously, the intensity and duration of natural shocks often made all the difference between survival and catastrophe. Societies that could withstand one drought year with only hunger could not withstand two without starvation. Second, and equally obviously, some societies had, by design or accident, less in the way of buffers or resilience than others.

Societies that had few or no domestic animals, for example, could not survive a harvest failure, as reliably as could another which could eat its animals one by one. Societies that had poor transport infrastructure could not import food as readily (or cheaply) as could others with good roads, canals, or (eventually) railroads. Nor could the isolated receive government or charitable assistance as easily, if it was in the offing.

Societies, such as early 20th-century rural China, which used nearly every available acre as farmland and preserved very little in the way of woodlands, wetlands, proved more vulnerable to flood than did others that (by accident or design) kept land in reserve. Societies without active and able public health systems suffered more from epidemics than those that had such systems.

Less obvious, perhaps, were differences in levels of ecological ignorance. Populations which have lived in one environment for several generations gradually acquire, and usually take pains to transmit, knowledge of how to survive and prosper within the limits of their environment. They also gradually form a sense of the boundary conditions to be expected, and know, from oral tradition, that they must be prepared for adversities – locust invasions, prolonged drought, and so forth – beyond their own personal experience.

Populations present for dozens of generations normally had exquisite ecological knowledge, and knew where to find edible plants to see them through famine, where to find underground water when there was none on the land’s surface, and so forth. Such knowledge contributed materially to resilience.

Conversely, in many instances, especially in the last two centuries (because of cheap transportation and more long-distance migration), many populations found themselves operating experimentally in new environments. This was true of the British and Irish settlers in Australia after 1788, who inevitably misunderstood antipodean ecology, and often paid a price for it.15 It was true of the American farmers on the southern plains in the 1930s, almost all of whom came from more humid climes and in the 1930s drought naturally presumed that the moister years of 1915-30 were normal.

They were ignorant of the cyclic drought patterns of the plains, and inadvertently turned a routine drought into an epic Dust Bowl. Ecological ignorance also lay behind the failures of the Soviet Virgin Lands scheme of the 1950s, in which Premier Nikita Khrushchev ordered an area of dry Siberian steppe land the size of California to be planted with wheat, only to see within a few years disastrous drought, dust storms, and harvest failure.

2The best study remains Jean Grove, The Little Ice Age (Cambridge: Cambridge University Press, 1988).
3William H. McNeill, Plagues and Peoples (New York: Doubleday, 1976) remains the most useful survey of disease history.
4On the AIDS epidemic mortality, Kenneth Mayer and H.S. Pizer, The AIDS Pandemic: Impact on Science and Society (New York: Academic Press, 2004), 2.
5For high-end figures, Mike Davis, Late Victorian Holocausts (London: Verso, 2002)
6V.K. Sharma and A.D. Kaushik, “Floods in India,” at: http://www.nidm.net/Chap6.htm. Xia Jun and Y.D. Chen, “Water Problems and Opportunities in the Hydrological Sciences in China,” Hydrological Sciences 46(6), 2001:907-21. Gerd Tetzlaff et al, “Das Jahrtausendhochwasser von 1342 am Main aus meteorologisch-hydrologischer Sicht,” Wasser und Boden 54(2002), 41-49.
7Neglecting the Johnstown flood of 1889, a case of a burst dam, which killed 2,200. This I consider not one of nature’s shocks, but a case of engineering failure.
8Jelle Zeilinga de Boer and Donald S. Sanders, Earthquakes in Human History (Princeton: Princeton University Press, 2005). By far the most serious eruption from the human point of view took place around 74,000 years ago, at Lake Toba, Sumatra, which ejected 2,800 times as much material as Mt. St. Helens, covered Malaysia in up to 9 meters of ash, put ten billion tons of sulfuric acid into the atmosphere producing acid rain of a unique intensity, lowered global temperatures 3-4 degrees Celsius, and according to one interpretation of mitochondrial DNA evidence, brought the human race to the brink of extinction. This was the biggest eruption of the past 2 million years.
9The rich world since 1919 has of course lived with the specter of war and since the 1940s with the risk of nuclear annihilation.
10Mark Cioc, The Rhine: An Eco-biography (Seattle: University of Washington Press, 2002); David Blackbourn, The Conquest of Nature: Water, Landscape, and the Making of Modern Germany (New York: Norton, 2005).
11Jacques Dupâquier et al, Marriage and Remarriage in Populations of the Past (London: Academic Press, 1981).
12Pierre-Etienne Will and R. Bin Wong, Nourish the People: The State Civilian Granary System in China, 1650-1850 (Ann Arbor: University of Michigan Center for Chinese Studies, 1991).
13Matthew Mulcahy, Hurricanes and Society in the British Greater Caribbean, 1624-1783 (Baltimore: Johns Hopkins University Press, 2006); Zeilinga de Boer and Sanders, Earthquakes, 128; David P. Forsythe, The Humanitarians (Cambridge: Cambridge University Press, 2005).
14Cormac Ó Gráda, “Making Famine History,” Journal of Economic Literature 45(2007), 5-38.
15Tim Flannery, The Future Eaters (New York: Bazillier, 1994)