Real Threats

In my book, 2012: Extinction or Utopia, I make a list of the various threats that face our planet, politically, socially, environmentally, and naturally, in an effort to appraise just how likely any of them are really to do us in. While the prospect of our own demise is always a guessing game, I thought the reader might find it helpful to look over my list and judge for themselves whether they agree with my assessments or not. Of course, you might even come up with a few of your own that I have overlooked, in which case drop me a post and let me know.

Alright, so just what are the threats to Mother Earth? Below is my chart of potential threats to the planet, both man-made and natural, along with what I consider to be their destructive potential to destroy, in turn, a global civilization, life in general (not just human beings, but all life on the planet) and the environment, rated on a scale of 1 to 5 (with 1 representing the lowest potential for destruction and 5 the highest):

Notice that many of the natural causes we traditionally assume to be the most destructive are really not the most serious threats we face. Earthquakes, for example, while extremely destructive, are localized events that may level poorly built structures and change the flow of a river, but have almost no impact outside of the quake zone itself. This is also true for seismic (commonly but mistakenly called tidal) waves which, while capable of inundating miles of coastline and devastating a coastal city, could hardly destroy all civilization on the planet. But there are a few on the list that really could be a major threat, so let's take a closer look. First, the natural doomsday threats:

Super Volcanism: An ordinary volcano, while inarguably destructive, are largely localized events that impact only those cities and population centers within a few dozen miles of the eruption site, and while big eruptions are notorious for spewing millions of tons of material into the upper atmosphere, which in turn has the ability to impact weather patterns hundreds or even thousands of miles from the eruption site, such effects are usually short-term and not particularly dangerous. However, there are two exceptions that could spell—if not doomsday—certainly great hardship for the planet in general. The first of these would be a series of large volcanoes erupting over a comparatively short span of time whose cumulative effect could seriously threaten crop production worldwide, potentially resulting in world-wide food shortages and creating significant social upheaval. While there have been periods in the geological past when this was the case, however, it seems the likelihood of dozens of eruptions occuring in a comparative short span of time (say several months) world-wide is extremely unlikely. Not impossible, of course, but so remote as to be essentially a non-concern.

However, there is something known as a "super volcano", which is an eruption large enough to devastate an entire continent as well as drastically affecting the planet's environment for decades afterwards. The largest one that we know about occured at Lake Toba, Indonesia, over 75,000 years ago—an eruption which may have, by some estimates, killed 60% of all human beings on the planet and profoundly impacted the weather on the planet for decades. Were one to occur today, it might not spell the end of civilization, but it would certainly mess things up pretty substantially. However, while the effects would be significant and, in areas, devastating, our technological capability would probably enable us to offset the worst effects, at least within the more advanced nations on the planet. Obviously, developing nations would bear the brunt of such an event, likely resulting in the death by famine of hundreds of millions of human beings (with livestock deaths numbering in the billions), but within a few decades civilization—battered and bruised, perhaps, but still quite intact—should be back on its feet.

Fortunately, however, such eruptions are rare (at least as far as human life-spans are concerned): the last really massive super eruption occurring around 26,000 years ago at Lake Taupo in New Zealand. Additionally, and as far as we can tell, only America's Yellowstone Caldera is also capable of putting on such a show, having done so twice in the last two million years, the latest occurring just over 640,000 years ago. Big eruptions such as Krakatoa (and even more environmentally destructive eruptions such as Mount Tambora in Indonesia in 1815) are essentially once-a-century events, while the type of super eruptions of doomsday lore are once every 100,000 year events, making the prospect of doomsday coming in the form of massive volcanic blast and a sky blackened with ash a remote one.

Asteroids, Comets, and Meteors: Of course, volcanoes are not nearly as popular a doomsday scenario as is the prospect of a comet or an asteroid hitting the planet (an especially spectacular doomsday scenario popular with Hollywood) which, depending upon the composition and size of the celestial object, really could spell the end. Just such an asteroid, in fact, is thought to have exterminated the Dinosaurs some sixty-five million years ago, while similar celestial objects may have been responsible for other mass extinctions throughout history. As such, if we were looking for a natural agent to herald in doomsday, this could well do it.

What makes such celestial objects especially scary is the fact that they can theoretically appear at any time with only minimal warning (in some cases, no more than a few weeks) and, if large enough, could truly trigger a genuine doomsday scenario. Additionally, these objects don't need to be especially large to do damage. According to best estimates, the one that wiped out the dinosaurs was only about 10 kilometers (6 mi) in diameter, which is not much bigger than Mount Everest. However, even at such a comparatively small size, it produced a crater over 112 miles in diameter and exploded with the energy equivelent of 100 trillion tons of TNT, or about 2 million times greater than the most powerful thermonuclear bomb ever tested! Fortunately, ones like the monster that did in the dinosaurs are a once every 100 million year event, so we theoretically should have another thirty-five million years before we need to start worrying.

Fortunately, space is a big place, making the chances of a large one of these errant rocks pelting the planet pretty remote. While estimates vary considerably over how grave a threat asteroids and large meteors pose to the planet, the chances of one ending life on the planet anytime soon is variously estimated to be anywhere from one in 10,000 to as low as one in ten million. However, large meterorites are more problematic than asteroids because they are so difficult to detect and can appear quite suddenly. Additionally, even a small one—say no larger than the size of a typical home—is capable of leveling a small city, so the danger can't be entirely ignored.

Comets, however, are another story. Despite being composed primarily of frozen gas (which makes them considerably less dense than an asteroid or meteor) they are just as potentially destructive. By way of an example, when the comet Shoemaker-Levy 9 hit the planet Jupiter in July, 1994, the pieces of that comet (which was actually a shattered comet moving in formation) entered the Jovian atmosphere at an average speed of 130,000 mph (60 km/s) and delivered the energy equivalent of 200,000 megatons of TNT. And these were the one kilometer-sized fragments. Some were even larger and more destructive than that!

Additionally, there is evidence that a comet may have exploded over Earth as recently as 1908 over the Tunguska River in Russia, leveling an estimated 80 million trees over a 2,150 square kilometer (830 square mile) area and producing a 5.0 Richter scale earthquake capable of being detected on seismic equipment as far away as London. Estimates of the energy of the blast range from 5 megatons to as high as 30 megatons of TNT, with 10-15 megatons the most likely yield (which is still a force about 1000 times as powerful as the bomb dropped on Hiroshima, Japan in World War Two). Though science is uncertain whether the explosion was caused by the air burst of a large meteoroid or comet fragment, there is general agreement that the object was no more than a few tens of meters across, but even at that size, had it hit a major city, it would have leveled it and potentially killed millions. Not to worry, however. Scientists estimate that small comets capable of destroying a city only hit the Earth once every 40 million years or so. Big continent-busting comets like that in the 1998 movie Deep Impact, are rarer still, only hitting once every 150 million years or so. Still, one can never be too careful so keep your eyes on the sky, bucko!

Gamma-ray burst: Gamma-rays are inimaginably powerful bursts of energy that result from the merging of two collapsed stars. They are so powerful, in fact, that if one occurred as far away as 1,000 light years, it would appear about as bright as out own sun and would quickly cook off our atmosphere and destroy the ozone layer. This would result in ultraviolet rays from the sun reaching the surface at nearly full force, causing skin cancer and, more seriously, killing off the tiny photosynthetic plankton in the ocean that provide oxygen to the atmosphere. The problem is that such a double star is invisible to us, meaning that if one was nearby and did burst, we would have little or no warning, making for a true doomsday scenario. Fortunately, it appears that such beasts are rare, with the few that scientists have observed over the years coming from distant galaxies. And even if one went off in our own galaxy, considering the vast size of just our own humble little Milky Way, the chances of one occurring close enough to cause a problem is unlikely.
Rogue black holes: Over the past twenty years or so black holes—those invisible little vortexes of intense gravity left over from collapsed stellar corpses—have become increasingly popular as potential planet killers and for good reason: even a small one could cause all sorts of problems if it were to make its way through our solar system. So great is its gravitational pull that it would likely alter the orbit of some of the planets and, if it got close enough to Earth, draw us into an elliptical orbit that would create all sorts of extreme climate swings. While the likelihood of it actually colliding with Earth itself would be extremely remote, in a more reasonable worst case scenario it could toss us out of our orbit entirely and eject us out of our system. Additionally, it is estimated that there could be as many as ten million black holes in the Milky Way Galaxy alone, making the prospect of encountering one a little more likely.

How likely? Well, not very, actually. They don't move fast (no faster than a normal star) meaning that if one approached our solar system we would have decades or, if we were technologically advanced enough, even centuries to notice its approach (which would be done by noticing minor variations in the orbits of some of the outer planets as the beast affected their paths). Of course, there wouldn't be much we could do about it at that point beyond possibly evacuating the planet and heading into deep space, and in any case, it wouldn't be a sudden event but more like a long-term doomsday scenario that lasted for many decades.
Giant solar flares: Our sun is a pretty irritable cosmic partner, constantly shooting gaseous plumes of white hot plasma thousands of miles into space which our atmophere generously shields us from. Normally, they are not a problem, but sometimes these plumes are much larger than normal, and are what we refer to as solar flares (more properly known as coronal mass ejections). Fortunately, we seldom feel the effects of these plasmic bursts (beyond creating havoc for ham-radio users and increasing the luminosity of the Aurora Borealis or Northern Lights). However, astronomers have occasionally witnessed other suns in our galaxy produce something called a super flare millions of times more powerful than their regular cousins which, if it occurred on our sun, would turn our planet into a charcoal briquette. Fortunately, there is persuasive evidence that our sun doesn't engage in such foolishness, and that such massive flares seem to be confined mostly to newer stars or to those demonstrating significant gravitational instability.
However, our sun may be capable of exhibiting milder but still disruptive solar activity potentially capable of raising temperatures on Earth enough to induce massive flooding or, in the case of a decrease solar activity, lowering the temperature enough to induce a mini Ice Age (which would be far more destructive to the world's economy than is global warming). This is not end-of-the-world kind of stuff, however, but more of a long-term global change problem.
Reversal of Earth's magnetic field: It seems that every few hundred thousand years Earth's magnetic field dwindles to practically nothing and then gradually reappears with the north and south poles flipped. Now this flipping of the magnetic poles—the last one happening about 780,000 years ago—isn't particularly dangerous, but this brief period of decreased magnetic fields could threaten life on the planet, for without magnetic protection, particle storms and cosmic rays from the sun, as well as even more energetic subatomic particles from deep space, would strike Earth's atmosphere, eroding the already beleaguered ozone layer and causing all sorts of problems to both man and beast (especially among those creatures that navigate by magnetic reckoning). Further, scientists estimate that we are overdue for such an event and have also noticed that the strength of our magnetic field has decreased about 5 percent in the past century, possibly signalling that such an event may be in our immediate future.

However, in being so gradual, there should be plenty of time to take the necessary precautions to avoid the most destructive effects by moving underground or off planet, or perhaps strengthening the planet's atmospheric defenses through the use of exotic, futuristic technologies. In any case, it isn't something we need to worry about in the short term, though it could be a concern for those living a few hundred years from now.
Global epidemics: Germs and people have generally managed to coexist in peace for thousands of years, but occasionally the balance gets out of whack and all sorts of unfortunate things result (such as the Black Plague that wiped out a quarter of the population of Europe in the 14th century and the influenza outbreak in 1918-19 that took at least 20 million lives worldwide). As such, the prospect of a new antibiotic-resistant germ developing in nature that could decimate the world's population again is a very real one not to be taken lightly, especially considering the speed at which diseases can be spread nowadays. The grimmest possibility would be the emergence of a strain that spreads so fast that we are caught off guard or one that resists all antibiotics, perhaps as a result of our stirring the ecological pot. In fact, it is thought quite possible that the sudden wave of mammal extinctions that swept through the Americas about 12,000 years ago may have been the result of an extremely virulent disease which humans helped transport as they migrated into the New World.

However, there is good news as well. Science has come a long way since the 14th century—and since 1919 for that matter—in understanding how germs mutate, as well as in developing effective antibiotics for whatever new strains come along. This trend is likely only to continue into the future as new technologies and strategies for battling the constant assaults from our micrscopic preditors become more advanced as well, meaning that with luck, we should be able to stay just one step ahead of any future pandemics. That's not to say that a particularly virlent strain of influenza or an airborne version of the ebola virus might not someday appear to bring death to millions (especially in less developed countries) but the prospect of a single bug wiping out all of humanity overnight remains extremely unlikely (though not, of course, impossible). Pass the Kleenex, please.

Okay, that takes care of most of the natural threats, but what about those man-made dangers we face? Could we be sowing the seeds of Armageddon through our own technology? Let's take a look:

Thermonuclear War: Alright, I admit, this would be bad. Very bad. It's no wonder, then, that such a global conflagration taking place has been the leading preoccupation of doomsday prophets since Alamogordo and remains a shadow we have been living under for over sixty years. Additionally, with a planet bristling with literally thousands of warheads—some of them held in the arsenals of governments of questionable stability and with other developing countries in a race to produce their own weapons—such a possibility cannot be taken lightly. But could a full-scale thermonuclear exchange really eradicate all civilization on the planet, or are we overestimating such a nightmare scenario's true destructive potential?

At the risk of sounding creepily optimistic, however, the best computer models consistently demonstrate that despite the immense damage a full scale nuclear war would inflict upon humanity and the environment, it is unlikely to wipe out civilization in its entirety. It would set it back several decades to be sure and in some especially hard-hit areas civilization would have to essentially start over from scratch, but most likely humanity would survive, especially in the more remote areas of the globe. Additionally, much of the military and political infrastructure of the devastated countries—being largely mobile or protected in special facilities—would likely survive as well, thereby providing a basis from which to rebuild. While the industrial base would be shattered and the financial foundation of the global economy would be in tatters, as long as the basic knowledge and technological expertise acquired over the centuries survived, civilization would be able to rebuild. Certain areas might be rendered uninhabitable for years by radiation and the death toll might well be in the billions when all is said and done, but with a world population rapidly approaching the seven billion mark, there would probably be far more survivors than victims of even a global Armageddon. Not great, but survivable.
Nuclear Winter: Of course, the real danger from a thermonuclear war is not the blast damage and radiation; these would be fairly localized (most nuclear devices have a blast radius of between three and ten miles) and the radiation levels would drop fairly quickly to livable levels in most areas within a few years. What would have the greatest long-term impact would be the effect such an exchange would have on the Earth itself. The detonation of hundreds or, potentially, even thousands of nuclear warheads within the span of a few hours would throw up tremendous amounts of dust, smoke, soot and ash into the atmosphere, which would have a profound effect on the atmosphere and could even usher in something scientists refer to as "nuclear winter".

While a controversial and not completely understood phenomenon, the nuclear winter theory maintains that it is this secondary effect of a nuclear exchange that would do the real damage and ultimately kill far more people than the blasts themselves. In effect, this layer of dust and soot would be so thick, the hypothesis maintains, that little sunlight would be able to penetrate the gloom, resulting in a dramatic drop in global temperatures along with a sudden inability of plants to convert light energy into chemical energy via photosynthesis. This, in turn, would have a dramatic effect on Earth's intricately balanced ecosystem and agriculture, resulting in the devastation of the world's food supply and initiating a world-wide famine on an unimaginable scale which and potentially bring humanity to the very threshold of extinction.

However, the theory has a few problems. First, we simply don't know how much smoke and dust a full-scale nuclear exchange would throw into the atmosphere, how evenly distributed it would be, or if it would really be thick enough to prevent most sunlight from reaching the Earth's surface. Though we have evidence that large amounts of dust and other particulates in the upper atmosphere will decrease the amount of sunlight reaching the surface (the explosion of Mount Tambora in Indonesia in 1815, for instance, threw up so much ash that it ushered in a "mini Ice Age" that devastated crops in New England and Europe for months afterwards) that doesn't necessarily mean that a man-made catastrophe like nuclear war would do the same. Tambora ejected more than 160 cubic kilometers of material when it blew. The possibility that even 20,000 warheads exploding at once could put that much material into the air is extremely unlikely (especially as most of these would be airborne detonations unlikely to throw great amounts of soil skyward). Most of what would rise into the atmosphere would be smoke and dust rather than the heavier material ejected by a major volcanic eruption, making the denseness of the "blanket" considerably less than the ash cloud that would result from a super eruption. It's also likely that such a plume of smoke and dust, driven by generally lateral air currents, would be largely confined to the latitudes in which the majority of the detonations took place, leaving most areas (and, probably, the poles themselves) mostly clear. As such, it's uncertain how temperature over the entire planet would respond when sunlight is still capable of reaching large areas of the surface. Additionally, as the dust and smoke particles are heavier than the surrounding air, the clouds would dissipate fairly quickly—probably within just a few weeks—as the heavier particles fell back to Earth, eventually clearing the skies and allowing a degree of equilibrium to return to the planet. Of course, the clouds of smoke and ash would have profound detrimental effects on the ecology of the planet and drastically alter weather patterns for decades afterwards, but that these effects would be capable of extinguishing an advanced, global society in its entirety is uncertain and still open to debate.
Biological Weapons: The price of progress over the years is that today science has the capacity to produce weapons potentially deadlier than even nuclear weapons. Further, these deadly agents aren't explosive or radioactive, and are even too small to be seen with the naked eye, but in the wrong hands, they really could spell doomsday for humanity under the right conditions. Of course, I'm referring to biological weapons, which really do posses the capacity to kill billions, making their use a genuine nightmare scenario if they were to ever be used.

We're not talking about chemical agents such as Tabin, VX or Sarin gas here; while these weapons have the capacity to kill literally thousands of people were they to be unleashed on a major population center, nerve agents are not capable of obliterating a global civilization. Only biological agents have the capacity to cut through a population like a scythe, leaving cities and towns intact but utterly devoid of life. If it spread quickly enough and was especially virulent, it could eradicate the entire population of the Earth in a matter of months, leaving our planet entirely devoid of human life. Considering the fact that there are terrorists out there willing to give their lives for the "cause", the prospect of such a genetically engineered germ falling into their hands and of them actually using them on innocent civilians remains a reasonable cause for concern. It wouldn't be an overnight doomsday, to be sure, but if it ended in the extinction of humanity, it would be, for all practical reasons, the end-of-time as far as homo sapiens are concerned.

Fortunately, however, biologically exterminating an entire population is not easy. It takes a high degree of scientific and technological sophistication to create a viable agent, along with a high degree of foolhardiness to use it. People smart enough to produce such a germ are also smart enough to know it could well come back to haunt them as well, so the reluctance to use such a weapon would be considerable. Unfortunately, such restraints may not stop a terrorist bent on suicide, although even a terrorist should still recognize that the extermination of all life would be counter-productive to their goal; after all, one cannot install a theocracy on Earth or usher in a new age if there is no one left around to be subjected to it. Additionally, as is the case with naturally occurring pandemics, science should have the capacity to counter the effects of such a "super bug" were it to ever be unleashed. This idea works from the premise that any civilization capable of producing such a virus would presumably also possess the technology necessary to counter it. In effect, the higher the technology level, the more deadly the germ while, at the same time, the less chance the germ will be successful due to an advanced civilization's ability to counter it. As such, even if one were capable of working out the scientific, technological, political, military and moral problems developing such an agent would entail, its use could only be contemplated in the most desperate of circumstances.
Biotech disaster: One of the remarkable advances science has made recently is in the field of genetic engineering which, when done correctly, can make crops hardier, tastier, and more nutritious. Engineered microbes can also ease our health problems and gene therapy offers the promise of repairing elusive fundamental defects in our DNA, making the entire field an area of great potential. But there's a danger as well: genes from modified plants might leak out and find their way into other species, creating all sorts of unanticipated and unfavorable mutations, while engineered crops could foster insecticide resistance, making them especially vulnerable to pestilance. And of course there's always the possibility that a terrorist group might use such a technology to engineer an especially destructive weed (say one capable of destroying entire crops) or of even producing a mutated form of influenza or some other lethal pathogen. Fortunately, like bio-weapons, such would take an extremely sophisticated laboratory to produce, and how adversely they might impact our planet remains to be seen, though it seems one would be wise to err on the side of caution where the manipulation of DNA is concerned.
Particle accelerator mishap: Another often overlooked consequence of science is the possibility that one of our high-tech experiments might go awry, with all the unfortunate consequences that would entail. One of the more unusual concerns out there is the idea that a particle accelerator—those delightfully strange and super expensive donuts that fire atoms at each other at light speeds in an effort to see what happens when they collide—could set off a chain reaction that would destroy the world by inadvertently creating a subatomic black hole that would slowly nibble away at our planet until eventually it reduced to being just a cloud of dust orbiting the Sun.

However, just as fears that the first atomic bomb would start a sustained reaction that would set the atmosphere on fire proved to be unfounded, scientists claim that such concerns are likewise unfounded. The accelerators in use today simply aren't powerful enough to make a black hole and the fact that accelerators have been in operation for decades with nary a black hole to show for it should also be seen as an encouraging sign. Of course, maybe it's just a matter of building a big enough donut….
Nanotechnology Mishap: Though it has all the earmarks of a Star Trek episode, the fact is that science is just a few decades away from creating self-replicating microscopic nano-machines capable of performing surgery from inside a patient, building any desired product from simple raw materials, and doing other equally spectacular things otherwise beyond our capabilities. Clearly, nanotechnology has the potential to revolutionize manufacturing, medicine, and technology in a way scientists could not have imagined a few decades ago, making it an exciting and promising new field of study and one likely to grow in importance over the next few decades.

The problem is in what we don't know about this emergent technology. What if, for example, as a result of an industrial accident, bacteria-sized micro-machines spread through the air, replicating swiftly, and end up reducing the biosphere to dust in a matter of days? Plus, as they would also make superb military weapons (imagine what an army of nanobots could do to an enemy radar system or the inner workings of a nuclear submarine) consider how destructive they would be in the hands of terrorists. Clearly, such weapons would be disastrous and practically unstoppable. Most who work in the field, however, consider the threat overblown. Like the biological warfare scenario discussed earlier, such a weapon would prove too unpredictable to use, offsetting whatever advantages they may bring to the battlefield. Additionally, it shouldn't be difficult to figure out how to program the little devils to turn themselves off after a fashion, precisely to prevent such a scenario from happening . Still, one never can be certain where such technology will lead us, what it might be capable of doing, nor can we gaurantee we'll always retain control over it.
Artificial Intelligence: Speaking of nano-technology, another related technology has to do with the development of smart machines capable of thinking for themselves ala Commander Data of Star Trek fame. Of course, we're not talking about anything quite that sophisticated, but the idea of creating weapons capable of "thinking" of ways to confound an enemies' defenses, or a smart drone fighter capable of learning from previous engagements and adjusting its tactics accordingly isn't far away. Clearly, thinking machines would come in very handy in a number of ways and revolutionize our planet if they were to come to fruition.

The problem comes, of course, as to what if these smart machines got smart enough to decide that we're no longer necessary and do away with us clearly inferior biological units? Obviously, with their artificially enhanced reflexes and faster thinking speed they might prove a formidable enemy that really could prove dangerous if there were enough units involved—an idea demonstrated in graphic detail in the 2004 film I, Robot. Of course, that was Hollywood's vision of the future, but the prospect of a world awash in increasingly intelligent machines may be only a few decades away, making such a scenario not entirely beyond the realm of possibility, especially when one consider's man's occasional short-sightedness when it comes to the lethality of his own inventions.

But how great a danger is artificial intelligence? It all depends on how intelligent it is and what sort of safeguards might be built into it to keep it from becoming a threat. First, developing an artificial intelligence sophisticated enough to decide to do away with us "mere humans" is still a ways off (think centuries, not decades) and so not something we need to worry about for awhile. Second, it should be possible to program a failsafe system into any artificially intelligent machine we create forbidding it to harm human life (a concept proposed by science fiction author Isaac Asimov as early as 1942); and, finally, even if they were to take over, whose to say that smart machines might not make better leaders than humans do?

Seriously, though, while such a prospect may be a concern for future generations, it isn't something we need to worry about for the time being—if ever.
A bigger concern, however, would be the prospect of humans merging with machines—that is, of humans possessing the ability to essentially download their brains into computer-enhanced mechanical surrogates that allows them to log into nearly boundless files of information and experiences, making it possible for them to vastly expand their intellectual power. This would make such a person in essence a cyborg capable of far more than even the smartest and strongest human would be, and making them a particularly dangerous villain if they chose to go over to "the dark side." However, such a technology would probably be carefully regulated and monitored, and it's likely that such "postbiologicals" would still need regular human maintenance to keep going, so such a prospect is not a given. Also, it's not clear how a single cyborg—even a remarkably clever one at that—could initiate doomsday. It would still, after all, be limited physically and presumedly still be capable of being destroyed, making the prospect of computers ushering in doomsday most unlikely.
Environmental toxins: And finally there is the impact from our chemicals and waste products to induce the grim reaper to pay a visit. Certainly the death of thousands of people in an industrial pesticide accident in Bhopal, India in 1984 serves as a poignant example of just how dangerous chemicals can be. It's also uncertain how pesticides and thousands of other tons of chemicals we dispose of everyday might effect us down the road. In high doses, for example, dioxins can disrupt fetal development and impair reproductive function, potentially damaging our ability to procreate and so eventually driving humanity to extinction.

Of course, such a possibility is a very long-term doomsday prospect and not one most people normally think of when considering end-of-the-world scenarios, but if humanity is to one day die out, this is the most likely path it'll take. However, the fact that we are growingly increasingly aware of the problem that chemicals pose to us and our environment and that we are already beginning to take steps to address it (such as shifting to non-polluting renewable energy sources, etc.) should give us some cause for optimism. We may never be able to omit pollutants from our civilization entirely, but hopefully the future will be far cleaner and safer than the present (which in turn has already proven to be far cleaner and safer than our past).

The reader will note I leave out global warming as a possible threat, which is intentional. The effects of global warming (or cooling, for that matter) are gradual and uncertain, making the prospect of doomsday far less likely under this scenario. Additionally, the science behind all the hoopla is still far from decided, and seems to be more politically driven than scientifically valid. (Remember, it was only a few decades ago that scientists were pretty certain we were heading into a mini-ice age that failed to materialize, so caution where predicting future climate trends is always a good idea.) I do devote a chapter to looking at global warming in my book, however, in case you are interested in looking at some of the data (probably out-dated by now, but still interesting).