On any given weekday in the summer, you will find me walking through fields counting bugs. In fact, it’s my job: I’m an ecologist studying the communities of insects that live in agricultural landscapes. Most days between early June and early September I drive between farms to scout crop pests and the beneficial insects that eat them, changing sticky yellow glue traps and sweeping vegetation with a canvas net.

But a single afternoon in August 2006 stands out in memory. Along one of the transects my colleague and I had set up in a cornfield, we noticed that several plants around one of our traps were missing. Strong winds or hail can knock down whole corn plants but what made this remarkable was what stood in their place: marijuana. Specifically, there were five plants, each standing about eight feet tall, in the middle of our survey plot and bursting with buds ready to harvest. While we were deciding how to proceed and what to tell the landowners, we received our next surprise; someone else was rustling through the field towards us.

It’s rare to happen upon someone strolling through a cornfield—and for good reason. If you’ve never walked through one, it is not a pleasant experience. Tightly packed rows of stalks almost 10 feet tall create an almost full canopy overhead. Underneath, row widths much narrower than your hips include sharp, jutting corn-leaf edges that inflict papercut-like nicks to any exposed skin as you brush past. And if you’re there during the tasseling and silking stages, your skin may break out in a rash from the falling pollen. Appropriate attire for field scientists in cornfields includes boots, long pants, and sleeves, a sturdy hat, and glasses to protect your eyes from being cut by the leaves. In other words, anyone making the trek into a cornfield is going with purpose, whether to sample insects or surreptitiously grow marijuana.

When the person approaching saw us, our field gear, and our surprise, they quickly disappeared back into the dense sea of green stalks. While we never saw them (or their marijuana) again, it became clear that this was not an isolated incident. Almost every corn grower I spoke to that summer had a tale of discovering marijuana in their cornfields at harvest time. Which led me to ask: What is it about the nation’s largest crop that has made it so attractive to marijuana growers in recent years?

The answer: Growing marijuana has become possible and desirable, not to mention nearly untraceable, thanks to the very innovations that created industrial-scale, precision agriculture in the first place.

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In an arms race to grow more food for a ballooning world population while still turning a profit, commodity farmers are turning to quantification. By carefully monitoring their inputs and outputs, growers turn usage information into optimized and personalized plans for each of their fields. They map their field perimeters using GPS technology. They plant crops in laser-fine straight lines while streaming Netflix over wifi in their air-conditioned tractors, which count the seeds planted in real time. They precisely apply pesticides with helicopters, which are safer and more effective than crop dusters, reducing the amount of chemical needed. At the end of the growing season, they measure crop yield on a plant-by-plant basis as the combine harvests, revealing within-field patterns of variability never known before. Recently, agribusiness corporations have even proposed tracking that yield data at continental scales during harvest, which would be used to alter grain market prices into the next year. And while the Federal Aviation Administration has not yet legalized the use of drones for commercial purposes in agriculture, researchers have already started flying them over fields to record plant health and track pests, disease outbreaks, nutrient deficiencies, and drought stress at landscape scales.

All of this is possible without a corn farmer needing to step foot into the field, which is remarkable—and critical for several reasons. First, over half of American commodity farmers now call farming their secondary occupation, according to the most recent national agricultural census. And who has time to walk through a field when you have another full-time job? Second, commodity corn pricing forces growers to focus solely on the bottom line. They’re working to produce as much as possible, which lowers prices if everyone has a good year, while hoping for high selling prices, which depends on other growers having a poor year. (Harvesting 1 bushel, or roughly 70 pounds, of grain corn would get you $3.77 on the Chicago Board of Trade this winter.) Third, more and more agricultural land is being turned over to corn. In large part this is due to the push for corn as a biofuel feedstock. Lastly, the land cultivated by individual farms is increasing. Also according to the latest census, the average farm size is 434 acres — with over 336 million acres of land held by farms that are 5,000 acres or larger. This has led to amazing productivity in our country—America is the world’s leading producer of corn, harvesting nearly 376 million tons of it in 2012. How can a grower walk through all that land?

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