Apparently impossible for Australia as well, entirely girt by sea, and only 23million population. We also have significant knowledge and efforts in on-shore fish farming as well.
I am unsure how deep this study goes to understand capacity and capability, especially with regards to how each country could adapt.
We also fail at vegetables. But given we are highly leveraged in dairy for export, if we were isolated by trade we could switch up our land use. I am not saying it would be fool proof, but we can grow veggies here. We have an insane amount of arable land contrasted to our population.
Population here is over 27 million atm. [1] [2]
The idea we can simply change land use here seems simple too, but much of the agricultural industry has boxed themselves in, applying nasty BS to the ground which used to be not safe to grow veggies for 6 - 7 years bare minimum, though there has been of late, pressure to let the limit slide downwards for the idiots who could not be told that choosing a problem chemicals over some others which took a bit more effort, was going to bite them in the bum.
I have farmed veggies, but in a dry farming situation (no irrigation) so the whole show is at the mercy of the weather. Last few years have been a no go. Many other areas find themselves in a similar situation, water either costs and arm and leg or there's not enough access to it when required.
Ironically the best areas that grew a lot of veggies were (up until 60s, 70s) along the coast up my way Queensland ... much of it gave was to roads and houses that need wet weather insurance during very wet periods ... they are are subject to flooding.
The other factor that governs growing vegetables is the price being offered (knife edge to low) and silly antics like from Queensland sending truck loads of veggies 2000 km to a central depo and then back up along the coast for distribution.
BTW, for farmers, their fuel since the beginning of 2026 has doubled in prices after fuel excise rebate, so in a few months it's going to be very interesting as to what's in the shops that's still affordable by the average worker. The supermarkets here don't miss any upward costs either, applying the real cost by some factor the public might believe is realistic.
[1] https://www.worldometers.info/world-population/australia-pop...
[2] https://www.abs.gov.au/statistics/people/population