"Why Europe can't (won't) defend itself" Topic

Makes sense – that was the population of the UK in the early 18th century I think, just before the agrarian and industrial revolutions.

Better start stocking up !

It's reckoned that Britain's climate and geography can support, without any modern agricultural practices and technology, a population of approximately 6 million.

I assume that comes from the estimated pre-plague population of 14thC England. Its worth noting that by the Elizabethan period the UK could support over 3 million people on about a third of the country under the plough. Efficiency is also an issue medieval grain yields were up to four times less than modern ones and farm animal breeds substantially smaller. All things that wouldn't necessary evaporate over night – but 68 million wouldn't be sustainable without mechanisation or industrialisation.
There are also about 15 million odd people in the UK with chronic conditions, not all lethal in the absence of treatment, but you get the idea!

So … a lot of people are going to die it appears ?

From memory, the ‘One Second..' trilogy I referenced (fiction but seemingly well researched) predicted a 1-year survival rate of 40-50% in low population density agricultural states, 10-15% in semi-rural areas like North Carolina and less than 5-10% in dense urban areas, Florida etc, with an older, less healthy population and poorer access to food supplies.

Short answer … a lot of people will die …