The United Kingdom officially triggered Article 50 today, meaning the two-year march to Brexit has begun. The UK is leaving the European Union, and leaving without any concessions, any deals, any accommodations. It's the "hard Brexit." There are many reasons this is a bad idea, but let's keep it simple: the United Kingdom cannot feed itself.

Britain does manage to grow somewhere between 50 and 60 percent of the food it eats. The last numbers I saw were 54 or 55 percent. So better than half, but not nearly self-sufficient. And Britain does export some food and drink (read: beer), exporting things that its farmland and climate are good for and importing other things that it can't grow, or can't grow well. (If there are any British grapes, there should not be.) But the UK imports more than twice as much food as it exports. Britain depends on imported food from its neighbors, and has throughout its modern history.

Why is this? Because Britain's population is too large for Britain's own farmland too feed. Too many people on too small an area, with a good chunk of that area unfarmable. (Britain has plenty of lovely mountains.) They couldn't feed themselves if they tried. In fact, they have been trying, very very hard, and they can't.

This is not a question of farming more land: just about all the arable land is being farmed already. England has no field untilled, no stone unturned. And it is not a question of efficiency, because British farmers are already incredibly efficient, already wringing the absolute maximum yield from each acre. That they can feed more than half their massive population from that amount of land is actually pretty impressive. They cannot do better than they are already doing. In fact, they're getting close to some ugly short-term/long-term tradeoffs, where they could increase this year's harvest by a few percent at the cost of making the land less productive later. That is not a way out of their problem.

Now, the British are obsessed with British farmers. UK supermarkets slather their products with labels for British beef, British cream, British etc. etc. But that obsession just masks the basic problem that Britain doesn't produce enough beef, butter, and so on. The imperative to buy and cook home-grown products functions to distract the public from the larger problem that there's not enough home-grown food.

Likewise, British farmers are heavily subsidized by the EU, and this deal -- or rather, complete lack of deal -- kills those subsidies, which may or not be replaced. So this may hurt British farmers, too. But that complicated and murky policy question is much less important than the far simpler problem of not being able to feed your own population without buying food from other countries.

Where does most of that imported food come from? All over the world, but about half of the gap is made up by European Union farmers. Remember, England's traditional breadbasket is Ireland. It's been dependent upon Irish farming throughout its modern history. (Yes, even during the Potato Famine; Ireland exported food to England during the Potato Famine, and met its quotas, while the Irish themselves starved.) And of course, England's other nearest neighbor, France, is an agricultural powerhouse, blessed with acre after acre of prime farmland. So the EU produces more than a quarter of the food the British eat.

Now, I'm no economist. But it strikes me that if your country is dependent upon imported food, you never, ever want to leave a free-trade agreement. Tariffs on agricultural goods can only drive up the price of food for your people. God forbid you ever get into an actual trade war with the people who sell your citizens at least five meals a week.

Throwing up trade barriers on food makes that food more expensive, obviously. And, free markets being what they are, making one quarter of the country's food more expensive makes all food prices rise. If Irish beef is more expensive because of taxes, then people can charge more for British beef too, and will.

This makes daily living more expensive for everybody, but it hits poorer people much harder, because more of their income is taken up on basic necessities. Rich people spend a much smaller percentage of their income on food; even if they buy more expensive groceries, or go to fancy restaurants, it's a much smaller part of their monthly budget. (Having excess money for things beyond basic needs is what being rich is.) But if, say, one-third of your monthly income goes to the groceries, a spike in grocery prices can be truly painful.

The "elites" that Brexiteers love to jeer at are not going to be hurt by this; they will still have their French wines and their long lovely dinner parties. They will just pay a small surtax on those pleasures. It's the poor and hard-working Little Englanders, the people who voted for Brexit to stick it to the London elites, who will get it stuck to them at the supermarket checkout. They are the people who are going to be bringing home less bacon, and paying more for what they bring.

If this all seems like a stupid and self-destructive idea, well, Britain has never been Europe's farming superpower. But in the EU it's become the banking superpower, making enormous money as the financial capital of Europe because the whole bloc could locate its premier financial services in one city without worrying about financial borders. And now that those borders are returning ... oh, wait. What was the plan here again?