Civilization exists by geologic consent, subject to change without notice
For days now, the southeastern United States has been pounded by record tornado outbreaks. Just over a month ago, Japan experienced the third largest earthquake ever recorded by seismographs, followed by a devastating series of tsunamis that may have killed tens of thousands. Add this to the major recent earthquakes in Chile, New Zealand, and Haiti, or Hurricane Katrina in 2005, or the Boxing Day tsunami in the Indian Ocean in 2004, and the public is more aware than ever of the hazards of living on Planet Earth.
But before we overreact or act irrationally in fear of earthquakes or other natural disasters, we must step back a bit and put them in perspective. as I have done in my new book Catastrophes! Earthquakes, Tsunamis, Tornadoes, and other Earth-Shattering Disasters. Which ones cause the most damage? Which ones are the most dangerous to us in the short term? Which ones are dangerous in the long term? What things are most likely to kill you? What kinds of things are capable not only of hurting us as individuals, but destroying human civilization?
Psychologists have shown that human beings are notoriously poor at judging relative risks, and assessing which threats are really serious and which ones are exaggerated. For deeply-held psychological reasons, people are far more afraid of dying from a snake bite or in an earthquake, even though these are staggeringly improbable events for most people in the United States. Only 5 to 10 people die of snakebite each year. In the United States over the past century, earthquakes have killed an average of only 6 people per year. Yet because earthquakes are unpredictable and shatter our notion of “terra firma,” we are unjustifiably afraid of them. Because snakes trigger a primordial fear response in our brain, we are terrified of them. When we were small vulnerable hominids running across the African savanna, snakes were a real threat to us, because many African snakes, like mambas and cobras, are poisonous. But now that snakes are so heavily slaughtered in this country (despite the fact that most American snakes are non-poisonous), we are much more a threat to them than they are to us.
A more objective way of assessing real threats is to look at cold hard statistics, as an actuary or insurance adjuster does. A 2008 article by Borden and Cutter looked at deaths in the U.S. from all natural hazards from 1970 to 2004. Despite the fact there were several big California earthquakes (1971, 1987, 1994) and large hurricanes during that time window, you would never guess what the number one killer was. It was not even a topic that we think of as catastrophe, since it happens so often and so slowly. The top killers among natural hazards in this country are … heat waves, storms, and winter!
The ranked list of killer hazards and the percentage of the roughly 20,000 that died over that time window is:
- Heat and drought (19.6%)
- Severe weather (18.8%)
- Winter weather (18.1%)
- Flooding (14.0%)
- Tornado (11.6%)
- Lightning (11.3%)
- Coastal hazards, like drowning (2.3%)
- Hurricanes and tropical storm (1.5%)
- Earthquakes (1.5%)
- Landslides (1.9%)
- Wildfires (0.4%)
Yes, earthquakes, hurricanes, and other extreme weather events are terrifying disasters, but the biggest killers are slow and subtle: heat waves and drought. Likewise, we take severe storms and the bitter cold of winter for granted since they happen so often, but they kill a lot more people than more dramatic events like tornadoes, hurricanes, and earthquakes. Notice that hurricanes, earthquakes, and landslides are near the bottom of the list with less than 2% of the total deaths. Even though hurricanes and tornadoes are potentially very dangerous, we usually have some warning of when they are coming, and most people take shelter or evacuate when warned. Volcanic events did not even make the list, since the small Mt. St. Helens eruption was the only deadly volcanic event in this country for better than a century.
Borden and Cutter also plotted the risk on a map of the U.S., organized county by county. If you asked anyone where the most dangerous places to live in the U.S. are, they would probably guess California with its earthquakes and landslides and brush fires. But as the map shows, the opposite is true. Coastal California was one of the least hazardous in this regard (because we seldom get extreme killer weather of either hot or cold variety). The most deadly regions turned out to be the Deep South, where severe heat and humidity is common, and where occasional hurricanes and tornadoes only add to the carnage. Also dangerous was “tornado alley” in the southern Plains, with heat, drought, and tornadoes, and the southern Rocky Mountain region, with its desert heat and flash floods. The northern Plains and Rockies and Midwest were also death “hot spots” due to extreme cold and drought and occasional flooding. The rest of the country did not show any striking trends one way or another. What you don’t see is any strong correlation of high death risk with the fault zones map or even with the Gulf Coast-Florida hurricane zone.
Let’s put that in an even broader perspective. Many people are terrified of earthquakes and tornadoes and hurricanes, but these events are not something to lose sleep over except when there are clear warnings that a hurricane or tornado is coming. We should be more careful and worried about heat waves and severe winter storms, but we’re so accustomed to these each year that we don’t realize how deadly they are. But worrying about natural disasters looks absurd in the face of where the real risks come from: your cheeseburger and French fries, your car, cigarettes, and all sorts of things you encounter every day. Borden and Cutter point out that for the 20,000 people killed in the U.S. by natural disasters during the study period from 1970 to 2004, there were 652,000 deaths from heart disease alone (more than 30 times the natural disaster total)! There were 600,000 deaths from cancer (also 30 times the total from natural disasters). Of cancer deaths, almost a third were from lung and other cancers due to smoking. Colorectal cancer, pancreatic cancer, prostate cancer, and breast cancer were the other biggest killers. There were 143,000 deaths from stroke, 130,000 from chronic lower respiratory diseases (bronchitis, pneumonia), and even 117,000 killed in accidents (mostly car accidents). If we really took the issue of risk seriously and evaluated it objectively, we would do well to worry much more about our diet and exercise, get frequent health checkups, stop smoking, and modify our driving habits. We may fear death in an earthquake or hurricane, but lunch, cigarettes, and driving are much more deadly to you!
A Global Perspective on Natural Disasters
The story changes significantly when we look at natural hazards on a worldwide basis. In the U.S., the quality of our building construction in seismic zones, and our relatively good health care and emergency services, means that even big earthquakes result in relatively little loss of life. In many underdeveloped countries like Turkey, Iran, Armenia, Pakistan, Haiti, and China, and even European countries like Greece and Italy, earthquakes have a much higher death toll. The single biggest factor is the construction of their buildings. Most are built of simple stones or bricks held together by mortar, known as “unreinforced masonry”. Those buildings are death traps in even a mild earthquake, since they shake apart and then collapse with tons of weight on the trapped inhabitants, killing thousands. By contrast, in seismically risky areas like California, most older brick buildings have already shaken down in earlier earthquakes, and the codes forbid any masonry except reinforced bricks, where steel tie rods and rebar is threaded through the holes in the cinder blocks to hold them together when shaken. For much of the Mediterranean-Alpine-southern Asia earthquake zone, however, the population is too poor to afford more expensive but seismically safer construction (and their governments do nothing to prevent it). Even as the survivors dig out their dead, they are rebuilding the same death traps with the same old bricks in the same way. In some cases, like the 2008 Sichuan earthquakes in China, or the 1985 Mexico City earthquake, buildings may be built of modern safer materials but still become deathtraps because of political corruption and shoddy construction.
The global list of the deadliest natural disasters (see below) also includes a lot more flood deaths than we would find in the U.S. Most of these killer floods occurred in China. Their deadliness was exacerbated by political weakness or ineptitude in providing disaster relief, plus the fact that China has huge populations of peasant farmers living on floodplains with no place to go in event of a disaster. The same could be said for the effects of big typhoons, cyclones, and tsunamis in the Philippines, Bangladesh, China, and Burma. Events such as the recent Cyclone Nargis in Burma were made far deadlier than necessary by the huge populations of poor peasants living on low-lying ground and vulnerable to big storms, and governments that can’t or won’t provide warnings or timely evacuation plans, or disaster relief in any large-scale meaningful way.
|Rank||Event||Location||Date||Death Toll (Estimate)|
|1.||1931 China floods||China||July–November, 1931||1,000,000–4,000,000|
|2.||1887 Yellow River flood||China||September–October, 1887||900,000–2,000,000|
|3.||1556 Shaanxi earthquake||Shaanxi Province,
|January 23, 1556||830,000|
|4.||1970 Bhola cyclone||Bangladesh||November 13, 1970||500,000|
|5.||1839 India Cyclone||India||November 25, 1839||300,000|
|6.||526 Antioch earthquake||Antioch, Byzantine Empire||May 20, 526||250,000|
|7.||1976 Tangshan earthquake||Tangshan, Hebei,
|July 28, 1976||242,000|
|8.||1920 Haiyuan earthquake||Haiyuan, Ningxia-Gansu, China||December 26, 1920||240,000|
|9.||1975 Banqiao Dam flood||Henan Province,
|August 7, 1975||90,000–230,000|
|10.||2004 Indian Ocean tsunami||Indian Ocean||December 26, 2004||229,866|
Once again, however, we must put these natural disasters in perspective. Hundreds of thousands of deaths in an earthquake or cyclone or flood sounds terrifying until we stack them up against the true killers: disease, famine, drought, and other slower but deadlier agents. If the table listed the mortality rates due to all deadly world events, all top ten events would be diseases and famines, and no natural disaster would make the top ten. The drought in India that led to the Great Famine of 1876-1878 killed at least 25 million people, at least six to 25 times as many as any natural disaster on the list in the table. The 1918–1920 outbreak of Spanish influenza killed at least 20 million to as many as 100 million people, far more than any natural disaster in human history. The great bubonic plague or “Black Death” outbreak of the 1300s may have killed even more, possibly as many as 75 million to 200 million, but the death estimates are very uncertain.
The common diseases kill even more than the time-constrained “events” and “epidemics.” Although the medical world is justifiably proud of containing it, smallpox killed at least 300 million in the last century alone, and nobody knows how many humans have died of smallpox over the centuries. Measles killed more than 200 million over the last 150 years, despite the fact that it has been virtually eliminated in the U.S. Malaria killed 80-250 million people in the last century, even though there are lots of ways of mitigating its spread and deadliness. Tuberculosis killed 40-100 million people in the last century, and its death rates are increasing as the world’s skies become more polluted, and cigarettes become more and more popular outside the U.S. Even AIDS, which is a relatively young epidemic (spreading only since the 1980s) has killed more than 25 million people worldwide, far greater than any natural disaster.
We are impressed with large and terrifying events like tornadoes and landslides and blizzards, but as we saw with U.S. statistics, they don’t even rank. On a worldwide basis, many of the more terrifying disasters in history are pikers when compared to death tolls such as those caused by diseases and famines. The world’s deadliest tornado killed only 1300 in Bangladesh in 1989. The world’s worst avalanche killed 96 in the U.S. in 1910. The world’s deadliest blizzard killed 4000 in Iran in 1972. The world’s deadliest landslide killed 20,000 in Venezuela in 1999. The world’s worst wildfire killed about 2000 in the U.S. in 1871. The world’s biggest historic volcanic eruption, Mt. Tambora in 1815, was a bit more impressive with 92,000 deaths, but still this doesn’t come close to cracking the Top Ten list. And the great heat wave that fried Europe in 2003 was the deadliest ever with over 23,000 deaths, but that still does not make the Top Ten list, either. However much we are impressed by spectacular catastrophic events like volcanoes and tornadoes and landslides and blizzards, let’s not mistake the terrifying power of these events with the mortality they cause. Disease and famine are a lot slower and less dramatic, but still far greater purveyors of death than any rapid catastrophic natural event.
If you’re in Southern California on May 15 and have the time, come hear me speak about the topic at the last Skeptic Society meeting of the year, at 2:00 in Baxter Auditorium at Caltech.
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of their true risks,