When Hurricane Florence struck North Carolina last fall, floodwaters swamped vast stretches of farmland and graphically demonstrated a threat this part of the country is particularly vulnerable to: massive volumes of animal waste overflowing into waterways.

North Carolina has one of the world’s largest concentrations of industrial pig farms, with more than 2,000 operations involving a total of about 10 million hogs. Most store manure in open-air pits called “lagoons,” and when these overflow they can contaminate waterways with pathogens, pharmaceuticals and nutrients that pose serious pollution and health risks. Environmental watchdogs are on the frontlines of monitoring such overflow events and tracking the damage, both in North Carolina and from other livestock and poultry farms around the country. But first they need to actually find the industrial farms—many of which are not legally required to make their locations publicly available. This forces would-be monitors to manually pick out farms from satellite and aerial imagery—a task that can take months (or, in the case of one state agency in Iowa, longer than three years) to complete.

But researchers at Stanford University have found a way to pinpoint these farms in a fraction of that time, by using machine learning to train a computer model to identify them. “We realized this was exactly the kind of place where we could leverage the really rapid advancements in computer vision,” says Stanford law professor Daniel Ho, who co-authored a new paper on the technique, published in Nature Sustainability this week.

Ho and his team focused on farms called concentrated animal feeding operations (CAFOs). These are defined as containing more than 1,000 beef cattle, 2,500 pigs or 125,000 broiler chickens for more than 45 days. CAFOs across the country churn out roughly 335 billion tons of manure each year—but they are not required to treat it in the same way that jurisdictions and homes must treat human waste. “When a single CAFO can produce as much manure [fecal waste] as a medium-sized city,” Ho says, “how do we ensure that the waterways of the United States are protected?”