A Michigan chapter of the American Federation of State, County and Municipal Employees is warning that somebody is coming to take union jobs. Not immigrants, not robots — but goats.

After Western Michigan University rented a crew of 20 goats to clear weeds and brush this summer, AFSCME “filed a grievance contending that the work the goats are doing in a wooded lot is taking away jobs from laid-off union workers,” according to the Detroit Free Press.

If you haven’t been paying attention, goat rentals are all the rage in landscaping right now. With their voracious appetites they can clear weeds and brush in areas that humans have a hard time reaching. They’re gentler on the environment than heavy landscaping equipment or chemicals. They will eat literally anything, including poison ivy.

If you’re a union representing guys who mow or clear brush for a living, you can see the threat coming from a mile away — even if said threat has two horns and four legs.

AFSCME’s warning got us thinking: Just how many jobs are really at risk from the rise of goat-scaping? What follows is a heavily simplified, back-of-the-envelope, it’s-Friday-afternoon-and-nothing-really-matters estimate of the potential impact of goat labor on the U.S. workforce. Are you ready?

The first thing we need to do is figure out how much land a goat and a person can clear in a given period of time. We’re going to assume the human is operating a tractor with a Bush Hog BH16 Single-Spindle Rotary Cutter attached. With a cutting width of 72 inches, the Hog can handle tree saplings up to 2 inches in diameter — perfect for the kind of rough undergrowth that goats are often deployed to.

We’ll assume our employee is running the tractor at about 3.5 miles per hour, the middle of the ground speed range recommended in the Bush Hog’s manual. According to the mowing calculator at tractordata.com, an information repository for all things tractor-related, that setup should be capable of clearing about 18 acres of land in an 8 hour workday.

There are, of course, literally hundreds of external factors that could influence this number. A worker using only a handheld trimmer — say, a guy working for a landscaping company — wouldn’t be able to clear nearly as much. Rough or varied terrain might require using a smaller cutter. Easier terrain could let you get away with going faster.

But this number this seems like a good, middle-of-the-road estimate for what one person could reasonably accomplish. It’s also more or less in line with rough estimates for brush clearing rates given in various online forums by people who do this type of thing for a living.

On to goats then. According to the pamphlet “Using Goats for Brush Control as a Business Strategy,” published by the Cooperative Extension at the University of Arkansas, “a general rule of thumb is that ten goats will clear an acre in about one month.” Sometimes it takes more goats, sometimes fewer. But that seems to be the average.

Now we need to standardize the time period to make the goat and human numbers comparable. If one person can clear 18 acres in a day, how many acres can they clear in 30?

We’re going to assume a normal worker who takes weekends, so call it 20 days of actual labor (or four five-day weeks). That works out to 360 acres cleared in a month by one person, compared to 1 acre cleared by 10 goats. Multiply 360 by 10 to get the per-goat work equivalent, and you find out that in a month, our typical human can do the brush-clearing work of about 3,6oo goats. Take that, goats! Humans rule!

But wait: Exactly how many worker-goats are there in the United States?

The unfortunate answer to that question is, “we don’t know.” The USDA does issue annual head counts of the nation’s goat population. But it only tracks subcategories like meat and dairy, the products goats have traditionally been used for. It doesn’t include newer innovations like weeding goats, yoga goats, therapy goats or pack goats.

But a September 2005 report from the USDA notes that goats can be multipurpose. “Since producers can be paid for grazing their goats in troubled areas, there appears to be a synergy to this type of operation with either dairy or meat (market kid) production,” according to the report. “Producers could receive payment for grazing and then sell kids or dairy products, thereby benefiting twice from their goat herd.”

So let’s assume worst-case scenario: how many jobs would be at risk if every one of the nation’s meat and dairy goats also had a side job clearing brush? Per the USDA there are about 2.5 million meat and dairy goats in the U.S. as of 2017. Divide that by 3,600 to determine how many human brush-clearing jobs they could replace.

Further divide that number by two, since we assume that brush-clearing happens only during the growing season (May through October, or half of the year), and we have an estimate of how many full-time equivalent human jobs are threatened by goats in a typical year: 347 full-time equivalent jobs.

That’s … actually not a lot of jobs. If you consider that only some unknown fraction of the nation’s meat and dairy goats are actually currently being used to clear brush, the number gets even smaller.

Again, this is a wild, back-of-the-envelope calculation subject to who knows how much error. It relies heavily on the assumptions above, which are probably wildly inaccurate in certain circumstances. If tractors aren’t available, for instance, humans lose a good portion of their advantage over goats.

But the overall degree of magnitude, or lack thereof, of the final number suggests that goats won’t be taking a bite out of the national jobs numbers any time soon.

None of which is any comfort if you’re a laid-off union worker in Michigan watching a goat do a job that was once yours.