What did you eat for breakfast this morning?

I posed that question to my Santa Clara University students last Friday during our late-morning lecture on the human population and its many impacts. I was pleasantly surprised: fully three quarters of the class had actually eaten something. As to what they had eaten, their answers were as variable as they were indicative of the consumption patterns of the American population: “Pop-Tarts”; “scrambled eggs”; “cereal”. One girl waved her half-finished energy drink in the air.

We took a moment to think about where breakfast – and our food in general – comes from. How much does it take to feed a person? Using modern technology, we can get about 155 bushels – the equivalent of 18 million calories – of corn off an acre of farmland. A quick back-of-the-envelope calculation reveals that someone determined to live on corn alone could get his or her 2,000 calories per day from as little as 1,700 square feet, less than a 4-yard sliver of an American football field.

That doesn’t seem like much.

But we hadn’t accounted for the unmistakable fingerprints of fossil fuel all over those ears of corn – and, as it turns out, the rest of our food supply. Modern agriculture relies on modern technology. We plant and harvest our crops with the aid of tractors and combines; we irrigate them liberally with water pumped from distant sources that – as we’re about to learn here in California – are just as important to our food supply as to our skiing season. We use modern chemistry to produce nitrogen-rich fertilizers and to manufacture the pesticides and herbicides that beat back the weedy organisms vying to take over our carefully tended fields.

Then, there’s the processing. Harvested crops are shipped off to large plants, ground, sifted, mixed, cooked, baked, and decorated, and then sealed up in airtight plastic and foil packaging for distribution to my students and myself – often hundreds of miles away from the 500-acre farm where corn tassels might have waved only a few weeks earlier.

All of these steps require energy. Lots of it. And these days, that energy comes from fossil fuels – from non-renewable seams of coal and reservoirs of oil extracted from progressively less accessible locations beneath the Earth’s surface. As the corn syrup-averse foodie knows from perusing nutrition facts, corn and its byproducts are found in just about everything. Even so, it’s hardly the only thing we eat. Nevertheless, modern agriculture employs the same energy-intensive industrial practices on almost all of our crops, and many of our animal husbandry systems as well.

There’s good reason for this: using technology, we’ve made massive gains in efficiency. By centralizing our crop production and taking advantage of breeding programs to select plants and animals that produce uniform, high yields, we’re also able to coordinate our efforts. While not cost-effective on a small family farm, tractors on large farms can harness fossil fuel energy to do the work of dozens of men, reducing the cost of labor and, by extension, the cost of the final food product.

Back in 1900, a third of the United States population worked long, rewarding, but backbreaking hours on farms. Today, only 1% of our population grows our entire food supply.

Though it has sometimes come at great personal cost, these labor and time savings have freed up members of our population to pursue other careers – some of which apparently involve sitting in my Environmental Science course. And using technology has taken some of the variability out of agriculture, enhancing our food security. Bad year for insect pests? Use some more pesticide. Dry year? Pump some more water. Crop failure? Draw on preserved stores or import from a more fortunate locale.

This technological revolution was so profound that one of its founders was awarded the Nobel Prize in 1970.

Despite its superficial promise, however, industrial agriculture is exceptionally perilous. It was developed at a time when oil was cheap, but the fossil fuels on which it relies are not renewable resources. It took millions of years to accumulate those energy stores – and it takes only a few minutes to peel back the lid of a single-serve yogurt container and spoon down its contents in the back of my lecture hall.

We’re already seeing food prices climb alongside energy costs. What happens when we have definitively passed peak oil? When does running those big tractors and mile-long water lines simply become too expensive? Sure, we’ve got our organic farms and buy-fresh-buy-local initiatives, but they account for a tiny – though growing – fraction of our food supply.

But one thing is for sure: We won’t be eating oil for breakfast forever.

Holly welcomes reader questions, comments, and breakfast food suggestions at hollyvm “at” stanford.edu.