An interesting paper by Mr. Jason G. Matheny, called "Reducing the Risk of Human Extinction" (last draft) notes that there is so far no analysis done of the cost-effectiveness of reducing human extinction risks. He provides a method of analyzing the cost-effectiveness of protecting against a mass-scale catastrophic event, using as an example case the threat of an asteroid impact.
Mr. Matheny's calculations show that at best, protection from asteroid threat costs can be as low as $2.50 per person per life-year - contrast this to the US health programs which can spend over $100000 per life-year!
Even if one were to assume that humanity would exist only for the next 1000 years (after 1000 years, *poof* we're dead), the price for asteroid protection would be $4000 per life-year, which is basically a bargain.
Of note is that even when discounting, for whatever reason, the value of future lives (=future lives worth less than lives now), the protection against asteroids would still be quite cost-effective. In practice, the discounting is not feasible for, for example, ethical reasons. Even at a high 5% constant geometric discounting rate, it would mean $200000 per life-year, for saving an expected 8 billion life-years (see section 8 of the paper for details). Even though more expensive, it will still be possible to handle.
The conclusion is: protection against this type of catastrophic extinction-level event is feasible and cost-effective. But just how feasible is the threat itself? In other words, how likely is an asteroid of hitting the Earth? And what would happen if a big one were to hit us?
A good example of what might happen can be seen from the extinction of dinosaurs. One theory behind this "K-T extinction event" is that it was due to one or more catastrophic asteroid collisions. The collisions did not kill off the dinosaurs instantly though - for example, one effect of the impact would have been a massive dust cloud which blocked out the sunlight and as a result, severely damaged the ecosystem. This in the end cut off the food supplies for the dinosaurs through killing off plants, and killing off smaller animals which the dinosaurs used as prey. There were also other effects, such as flaming debris falling from the skies, causing large-scale fires and thick smoke.
Although asteroid impact is low in probability, the impact is enormous - if it happens, there's a very high possibility of killing off humankind entirely or at least severely damaging the whole humankind and human culture as we know it.
A sufficiently big asteroid hitting Earth can simply annihilate human civilization on this planet within a short period of time. A smaller one, say over 1 kilometer in diameter would (depending on of course where it would hit) dramatically reduce the size of the human population and more of less collapse modern society due to the ensuing chaos.
For example, consider things such as:
- massive refugee movements which create instabilities in areas receiving the refugees
- climate damage which causes food crop failure, leading to famine - just like what happened to the dinosaurs
- economical impact in modern interconnected economy means severely damaged markets - just look at what the recent sub-prime loan triggered financial crisis did: a systematic failure, with cascading ripple effects around the world
- raw material supply chains will be destroyed or damaged, thus driving up prices of many goods
- martial law and/or military control, food rationing and so on imposed also in those inhabited areas which do not suffer direct effects from the impact
- diseases will be running rampant due to disruptions in health care systems, water services, sewer piping, etc.
The point is: if an asteroid larger than a certain threshold hits the Earth, even if you're not in the impact zone, not much will be normal anymore. Everything will be different. It will take many tens, if not hundreds of years to recover from such an impact.
So what can we do?
Continued in part II.