I'm sure the UK is reliant on imports in order to enjoy a full breadth of non-essential discretionary choices, and to sustain current levels of food waste. I think it could be misleading to describe that as "import dependent". If the UK lost all access to international trade, people would have to change their diets. Diets would contain more meat, fish, cheese, root vegetables and wheat. They'd contain less rice, processed food, sugar, and a narrower selection of fruits.
I've no doubt that a sudden cataclysmic change to international trade would spike food prices and increase poverty-derived food insecurity. But I doubt there would be physical calorie shortages.
There was already a preview of this a year or two ago, when there was a shortage of salad vegetables in the UK (Brexit + Covid + weather, I think). The government minister recommended eating turnips instead, as they were in surplus.
> I've no doubt that a sudden cataclysmic change to international trade would spike food prices and increase poverty-derived food insecurity. But I doubt there would be physical calorie shortages.
If there was a sudden change, there might be calorie shortages. However, I agree that if importing become more expensive over the longer run, or even if there was a quick change, but one that could be predicted years in advance, there would be no calorie shortages.
However, the same is true for lithium: the UK could mine its own lithium, if importing become infeasible. I am not sure though, if it would make commercial sense even then: you can make batteries (and other gadgets) without lithium, and for many applications you can make do without batteries at all.
Eg instead of solely driving electric cars with home-grown lithium batteries, on the margin I would expect more people to take the train.
I've no doubt that a sudden cataclysmic change to international trade would spike food prices and increase poverty-derived food insecurity. But I doubt there would be physical calorie shortages.