When I was growing up in the '80's I had a mate at school who's dad was a bit of a hippy. He was sure we were all going to be killed in a nuclear war, so bought a scrub block at Upper Landsdown and started building a fall out shelter. It was multi tasking as he did need the dirt for mud bricks for the house, but he also had a sizeable bunker when it was finished.
It is a good outlook to indoctrinate your kids with though. "Come on son, lets dig this bunker together as there is no future and everyone is going to die" to a 12 year old kid.... no wonder he became a lawyer
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I'm not sure how successful it would have been though. Fall out and bush fires would have killed his permaculture garden and the preserved food and bottled water would only last so long. I think I'd rather go up in the fireball than slowly starve with radiation sickness
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With everything being bar-coded and scanned these days, the supermarkets don't actually hold anywhere as much stock as they used to. A lot of the shelf packers job of an evening is to 'dress the shelves', where all they do is stack stuff at the front of the shelf to make them look fully stocked.
They rely on central warehousing and suppliers are expected to hold stock, which is great when the supply chain is working.
I lived in Brassall (Ipswich Qld) in 2011 when we had big floods. Our road that ran to the supermarket was under 10m of water, the supermarket also lost power, so after 3-4 days when no one could get in there the freezers were a bit manky. That place shut up shop and didn't open for 6 months (then struggled for another 2 years before going broke).
For us it was 3 days of inconvenience because of my wifes coffee addiction she ran out of fresh milk after 2 days. I have the dual burner stove, multiple car fridges/batteries etc. what was in the cupboard and the camping boxes, so cooking and washing wasn't a problem. The cat ran out of biccies though.
The people in Moggil on the other hand.... They were cut off for a week and lost power on day 1, so those that were set up for camping were well ahead. They had helicopters flying supplies across the river and people were elbowing each other in the throat over a loaf of bread!
The preppers that made me laugh are the ones that stock the house in the city with 16 ton of food, then plan to bug out. How many tins of tomatoes can you fit in a day pack?
Personally, I think it is better to invest your time and energy in forming a cohesive society, rather that withdrawing from it with a plan of cutting it away the first time things go pear shaped. Isn't that the whole idea behind a community?