If we did not import any food into the UK, how large a population could we sustainably support by producing our own? Fresh water is obviously an important consideration too.
鈥� If the UK were unable to import any food, the immediate consequence would be a massive market-driven change to a rural economy. The vast majority of British agriculture is devoted to producing meat, whether directly or through cereal crops grown for animal feed. But meat production is notoriously inefficient, typically requiring 10 times as much farmland as vegetables to produce the same amount of food 鈥� so meat would become more expensive.
To support our population, we would have to adopt a mainly vegetarian diet, perhaps enlivened by the odd sliver of mass-produced broiler chicken or factory-farmed fish. The countryside would be given over to vegetable production, with enormous acreages of beans, peas and other pulses. The south-east would probably be swathed in polytunnels.
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The irony is that if the UK adopted such a diet, people would live longer, healthier lives, leading to short-term population growth. If we also assume further mechanisation, intensive cultivation, cross-breeding, genetic manipulation and whatever extra innovations we come up with, within 30 years we could probably support a population around 10 times the current size 鈥� say half a billion people.
A lot of water would be required for vegetable production, but the UK is one of the best-watered countries of its size, with frequent rainfall. The problem is ageing infrastructure that fails to collect and transport enough water from the wet north and west, and instead insists on pumping streams dry to support a rapidly increasing population in the south-east. Reorganising the UK water-supply network would be expensive, but if the alternative was people starving, the money would be found.
Nigel Palmer, London, UK
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This article appeared in print under the headline 鈥淕row your own鈥�