Larry Stap’s fifth-generation family dairy farm has come a long way since his great grandfather established it in Lynden, Wash., in 1910. Now, as the 21st century gains ground in an ancient industry, Stap and his family have installed a robotic milking system that allows each of Twin Brook Creamery’s 200 cows to choose when and how often she wants to saunter into the milking parlor, where she enjoys a meal and gets milked—all without the need for human supervision. “Technology has always intrigued me," Stap says. “I don’t pretend to be computer savvy but I recognize you have to be always evolving and changing.”

The story of farming in the last century includes many examples of automated machinery boosting agricultural productivity and reducing the need for human labor. In 1900 around 41 percent of U.S. workers had jobs in agriculture, according to David Autor, an economist at Massachusetts Institute of Technology. By 2000 that figure had fallen to 2 percent. Nowadays a growing number of agricultural robots have boosted farming efficiency across the world, helping human drivers auto steer tractors in U.S. cornfields or replacing human workers picking strawberries on Japanese farms. But the rise of agricultural robots does not necessarily mean human workers will vanish from farms anytime soon. “There are really few tasks that a robot or automated platform couldn't perform as well as a human,” says Sara Olson, lead analyst of the Agro Innovation Intelligence unit at Lux Research. “But on the flipside, most growers will not cede total control to robots; that's why we've seen technology augment and assist rather than replace human labor.”

Robots can enable farms to become much more productive with fewer or the same number of human workers, Olson says. They can also spare the health of human workers by taking over backbreaking physical tasks and jobs such as pesticide spraying. Such advantages have helped boost a worldwide market for agricultural robots that was worth approximately $3 billion by the end of 2015, according to a report by the market intelligence firm Tractica. Forecasts suggest the market could jump to almost $17 billion by the end of 2020 and nearly $74 billion by 2024.

But the proliferation of robots does not automatically mean wholesale replacement of human agricultural workers. The U.S. Bureau of Labor Statistics estimates that the U.S. will lose approximately 110,500 jobs in agriculture and related industries between 2014 and 2024. In other words, agriculture's share of all U.S. jobs will decline from 1.4 percent to 1.3 percent in that 10-year timeframe. That pales in comparison to when agriculture's share of U.S. jobs fell by almost four percentage points per decade in the first 40 years after World War II.

Most developed countries have seen labor participation in agriculture decline rapidly in the past 100 years, says Eldert van Henten, a professor of agricultural science and head of the Farm Technology Group at Wageningen University and Research Center in the Netherlands. This is not just a case of automated machinery eliminating human jobs; many younger workers in developed countries prefer to avoid the “dirty, heavy, not prestigious work” of physical labor on a farm, van Henten says. Humanity may need robots to help feed the growing world population as the available agricultural workforce shrinks.

But many farms will still need human field hands. For example, robots still have a tougher time performing selective harvesting and precision maintenance of high-value crops. Such tasks will still require the “superior eye–hand coordination and intelligence” of humans before robotic capabilities catch up, van Henten says.

Robots could even help make farming “sexy” again for some human workers, Olson notes. Instead of doing backbreaking physical labor in the field, humans could do the easier work of supervising robot workers. Most agricultural robotic systems still require some form of human management, whether it involves watching over a swarm of bots to ensure nothing goes haywire or turning a strawberry-picking robot around once it has reached the end of a row. And farming operations have a strong incentive to want humans overseeing their cyber workers, Olson says. If a robot in a factory messes up a production run, the factory can simply correct the error for the following runs. But if a farming robot malfunctions during planting or harvesting, it could potentially wipe out a significant chunk of an entire crop—and a farm’s seasonal income.

Still, robotic assistance already makes good business sense for many large farming operations. About 10 percent of U.S. corn growers use GPS-guided Autosteer technology to help human drivers keep tractors and harvesting machines moving in straight lines and boost the accuracy of crop row spacing. Such technology sells for around $10,000 to $20,000 per machine and can pay off because of improved work efficiency and higher crop production. The average cost difference between Autosteer-assisted driving and the labor cost of humans doing manual driving could become negligible by 2019 or 2020, according to a Lux Research report. Improvements in automated steering and collision-detection sensors—perhaps leading to self-driving tractors—could eventually eliminate the need for a human driver on each tractor or harvester.

Environmental and health regulations also play a role in the rise of agricultural robots. In Europe laws that limit the use of agricultural chemicals and the exposure of human workers to such chemicals have already made lettuce-weeding robots competitive with human labor. Instead of human workers spraying herbicide on individual weeds, the lettuce-weeding robots can identify and mechanically cut weeds much more quickly and without the need for chemicals. Robots could also do the job of lettuce thinning by removing extra seedlings to ensure enough space for crop growth. The Lux Research report envisions robots doing the additional thinning job as cheaply as humans by 2028.

Although many farming robots are used on large, industrial-scale operations, they can also make sense for smaller agricultural businesses such as Japanese strawberry farms. This is because agricultural labor is both scarce and expensive in Japan, where the average ag worker is over 70 years old. Such high labor costs have already made a strawberry-picking robot as cost-effective as human workers, according to Lux.

Similar labor issues will also likely encourage more dairy farmers to adopt automatic milking systems, says Stap at Twin Brooks. He talks of labor costs, the reduced flow of immigrant workers coming to the U.S. and a lack of a solid work ethic in the next generation of American laborers. He also points out that robotic systems work without asking for vacations or weekends off, and never call in sick. He sees the construction and electrical cost of $750,000 for the robotic milking system—called the Lely Astronaut—as an investment in both a machine and reliable future labor. “What I really like about robots is the consistency," Stap says. "When our cows walk in, it's the same consistent thing.”

Such automatic milking systems got their start in the Netherlands during the 1990s. They have since caught on in northwestern Europe and countries such as Canada—places with notably high labor costs—but U.S. dairy farms have lagged behind. Stap's Twin Brook Creamery adopted the system after he needed to replace a worn-out milking facility. Even if automated facilities seem appealing, it often makes business sense for farm owners to get the most use out of their old equipment before replacing it. “Many dairymen have a million-dollar investment in the existing facilities, so they don’t just walk away from that to put in robots,” Stap notes.

Stap says the automatic milking system has enabled Twin Brook to save $5,000 per month on labor costs. No longer do human workers have to spend part of their time herding all the cows together for milking several times a day. Just as importantly, the cows—since being allowed to pick their own milking schedules—have been producing 20 percent more milk. The system also automatically monitors the quality of the milk and alerts farmers to individual cows’ behavioral changes that could signal health problems.

Robotic assistance has also allowed Stap to eliminate one full-time position that formerly required an employee to manually attach and remove “milking cluster” units that pump milk from each cow's teats. But the human worker who once held that job did not go unemployed. Instead, Stap moved him to an opening at Twin Brook's processing plant.