People might have to go back to living as people did a century or more ago. There are half a dozen events that could cause that to happen. Cataclysmic events have occurred before and it seems certain they will continue to repeatedly occur.
Scientists say that a large asteroid impact during the next few hundred years is unlikely because large impacts happen about every 30 million years. But there is that small chance that it could happen within a few years. Same thing with a huge volcanic eruption darkening the atmosphere with dust and changing the climate so much that crops will not grow.
But chances of other globally catastrophic events happening are harder to estimate. No one can determine the likelihood of an epidemic so severe that it would cause the present division of labor to shut down. And how could anyone predict the chances of an all-out nuclear war that puts huge amounts of dust into the air, blocking sunlight and causing the temperature to drop so that crops fail.
A global catastrophe that seems likely to happen soon is, by many acounts, global warming. Warming could be severe enough to cause widespread crop failures and famine.
And there are other possible scenarios. Nuclear technologies could produce nightmarish consequences. A runaway nuclear reaction in a fusion generator or an extremely high energy atomic collider could destroy the entire planet. Plus there are several other plausible catastrophic events.
It might not take a whole lot to cause a disruption in the distribution of goods and services. If people abandoned their jobs at, for example, power plants, to avoid a pandemic disease, then factories, hospitals, stores - you name it - would shut down.
Of all the possible global disruptions, the two most likely are global warming and a super pandemic. Pandemics such as the plague of the Middle Ages and the 1917 flu demonstrate that a pandemic is a likely possibility. People worldwide are now much more mobile, making the spread of disease more likely and much faster. Global warming has already started and seems likely to get worse as the huge populations of India, China, and the rest of the developing world adopt the CO2 emitting practices of the already developed countries.
There are some preparations that can increase your chances of survival if any global disruptions happened in our lifetimes. Nonperishable food can be stored to be used if food distribution is disrupted. Storing the food in your home might be sufficient for a short term emergency. For a long term disruption, it likely would be necessary to store the food in a remote location far from any population centers. Otherwise what you have stored likely would be taken from you by desperate starving people. You would also have to carefully store tools for gardening and cutting firewood, hunting equipment, and clothing.
You could not survive all imagined calamities at such a hideaway, but still, making the preparations will increase your chances for survival. Spend some time reading about catastrophes and ways to prepare for them. It is an involved subject that a person could spend all their time researching and making preparations. But with any amount of research and preparation you will be better off in a disaster situation.
Knowing that hundreds of millions of people will someday die from a catastrophe may give you a more somber outlook on life than you care to have. Use logic to keep things in perspective, it will not help to fret. That would take away from enjoying life. And it will hinder you from choosing what is best for your own welfare.
A 'can do' attitude favors successful preparations. The best thing to do is to plan a strategy, follow the plan, and feel good about doing what seems most prudent. A sense of accomplishment should be emphasized and savored whenever preparations are established. The human spirit and the ability to adapt may get most of us through difficult challenges without drastic consequences.
Alan Detwiler is the author of the ebook, Earth's Edge, a speculative science fiction novella describing a pandemic, global warming, and future science. Earth's Edge is available as a Kindle ebook at http://www.amazon.com/dp/B004UMP1HQ/ and as a Nook book at barnesandnoble.com