While we worry about gas prices, the costs of milk, meat and fresh produce silently skyrocket. So like the end of cheap energy, is the era of cheap food also finally over?

Since the farm depression of the early 1980s — remember the first Farm Aid concert in 1985 — farmers have gone broke in droves from cheap commodity prices. The public shrugged, happy enough to get inexpensive food. Globalization saw increased world acreage planted and farmed under Western methods of efficient production. And that brought into the United States even more plentiful imported food.

Continued leaps in agricultural technology ensured more production per acre. The result was likewise predictable: the same old food surpluses and low prices. My late parents, who owned the farm I now live on in central California, used to sigh that the planet was reaching 6 billion mouths and so things someday "would have to turn around for farmers."

Now they apparently have. Food prices are climbing at rates approaching 10 percent per year. But why the sudden change?

There have been a number of relatively recent radical changes in the United States and the world that, taken together, provide the answer:

Modern high-tech farming is energy intensive. So recent huge price increases in diesel fuel and petroleum-based fertilizers and chemicals have been passed on to the consumer.

The public furor over illegal immigration has, despite all the government inaction, still translated into some increased border security. And with more vigilance, fewer illegal aliens are crossing the border to work in labor-intensive crops like fresh fruits and vegetables.

The U.S. population still increases while suburbanization continues. The sprawl of housing tracts, edge cities and shopping centers insidiously gobbles up prime farmland at the rate of hundreds of thousands of acres per year.

In turn, in the West periodic droughts and competition from growing suburbs have made water for farming scarcer, more expensive — and sometimes unavailable.

On the world scene, 2 billion Indians and Chinese are enjoying the greatest material improvement in their nations' histories — and their improved diets mean more food consumed than ever before.

The result is that global food supplies are also tightening up, both at home and abroad. America has become a net food importer. We seem to have developed a new refined taste for foreign wines, cheeses and fresh winter fruits even as we are consuming more of our corn, wheat, soybeans and dairy products at home.

Now comes the biofuels movement. For a variety of reasons, ranging from an attempt to become less dependent on foreign oil to a desire for cleaner fuels, millions of acres of farmland are being redirected to corn-based ethanol.

If hundreds of planned new ethanol refineries are built, the U.S. could very shortly be producing around 30 billion gallons of corn-based fuel per year, using one of every four acres planted to corn for fuel. This dilemma of food or fuel is also appearing elsewhere as Europeans and South Americans begin redirecting food acreages to corn-, soy-, or sugar- based biofuels.

Corn prices in America have spiked. And since corn is also a prime ingredient for animal feeds and sweeteners, prices likewise are rising for poultry, beef and everything from soft drinks to candy.

There is currently more corn acreage — about 90 million acres are predicted this year — than at any time in the nation's last half-century. But today's total farm acreage is either static or shrinking; land for biofuels is usually taken from wheat, soybeans or cotton, ensuring those supplies grow tight as well.

In the past, the genius of our farmers and the mind-boggling innovation of American agribusiness meant that farm production periodically doubled. Indeed, today we are producing far more food on far fewer acres than ever before.

But we are nearing the limits of further efficiency — especially when such past amazing leaps in production relied on once-cheap petro-chemicals, fuels and fertilizers.

As in the case of oil, we've gone through these sudden farm price spikes before. My grandfather once told me that in some 70 years of boom-and-bust farming he only made money during World Wars I and II, and the late 1960s.

But this latest round of high food prices seems coupled to energy shortages, and so won't go away anytime soon. That raises questions critical to the very security of this nation, which may have to import as many agricultural commodities as it does energy — and find a way to pay for both.

The American consumer lifestyle took off thanks to low-cost fuel and food. Once families could drive and eat cheaply, they had plenty of disposable income for housing and consumer goods.

But if they can't do either anymore, how angry will they get as they buy less and pay more for the very staples of life?

Victor Davis Hanson is a classicist and historian at the Hoover Institution at Stanford University. Reach him at author@victorhanson.com.