I think we have more than < a responsibility to demonstrate how to feed our population from our own soils without destroying the planet>....we need to actually do it. Perhaps that's what you mean. Certainly there seems to be a view that just because WW2 is in the past, the need to feed ourselves from home grown produce has also passed. History shows us that it repeats itself, and famine will come to us too - we are an island, with a sea to cross, or air to fly through, in order to bring in food from abroad. Not to be able to do that could come from war or climate change, or some other disaster.
The rewilding fashion is not to blame for our reliance on imports. Cast your mind back a few years to 'set aside' when land owners were paid to leave their fields uncultivated, a sort of disorganised rewilding. The politics of trade agreements are way beyond my ken, but we do seem to be trapped in long term agreements to buy from other countries, for example Tesco is locked into a deal to buy a large amount of lamb from NZ, while we then have to find a destination abroad to which we can sell our home produced lamb. This has never made any sense to me.
I don't think there is any intention to rewild a large proportion of the country but it would make sense if what is rewilded was not previously good agricultural land - we are already growing crops for biofuels there. How would you justify that, any more than rewilding? Biofuels are a mockery, using as much energy to produce as they give out, and destroying vast tracts of virgin forests throughout the world so the rich can drive their gas guzzling cars, and warm their homes with their wood pellet boilers, and governments can feel smug and self satisfied.
There is so much wrong with the way we run our world, and until Climate Change is sorted, rewilding Britain is the least of our worries. At least rewilding allows more trees to grow to swallow up pollution, gives a home to our flora and fauna to maintain some of our biodiversity, and still produces plenty of food from the land
There are two sides to the view that by importing food we are taking that food out of the mouths of 'the world's poor'. The only way some countries can pay off their vast overseas debts, or earn money to import what they cannot grow or produce in their own countries, is to sell overseas ie to 'rich countries', including Britain. As long as the proceeds of selling overseas go to the population, not into the pockets of a few, of course.