Modern biotechnology could put dairy farms out of business. And not just dairy, but lots of other farms as well, including those that produce meat, leather, and even staple starches. In fact, the amount of land devoted to agriculture could shrink by 80 percent in the next few decades.

In the mid-1960s, when I was growing up on a dairy farm in the Virginia Appalachians, there were 3.2 million farms in the United States. About 600,000 of them produced some milk for sale. Nationally, there were just under 15 million milk cows, and dairy producing farms averaged about 20 milk cows per operation. (My family ran about 40 head of cows.) Fewer than 2 percent of dairy farms operated with more than 100 cows. Each cow produced a bit more than 8,000 pounds of milk per year, and the country consumed about 124 billion* pounds of milk annually.

By 2012, the number of farms with dairy cows had dropped to just over 50,000, and nearly 50 percent of cows lived on farms with more than 1,000 animals. The total number of milk cows dropped to 9.2 million, each producing about 22,000 pounds of milk per year. American consumption of milk had risen to about 200 billion* pounds annually. Dairy accounts for about 12 percent of all calories consumed by Americans annually.

Now the startup Muufri (pronounced moo-free) aims to use biotech to make perfect cow's milk. The lab-grown milk is a compound of six proteins and eight fatty acids. Cow genes are added to yeast grown in vats, from which those compounds are harvested. The company will add the proper proportions of minerals like calcium and potassium to the mixture. Muufri can leave out lactose, which 75 percent of the world's adults have trouble digesting.

The company's founders claim their milk won't need pasteurization, since it is produced in super clean lab conditions. By varying the ratios of the compounds, they can recreate goat's milk, sheep's milk, or even buffalo milk. And just like regular milk, Muufri can be turned into any other dairy product such as cheeses and ice cream.

Let's make the heroic assumption that Muufri or competitors completely replace the current dairy industry. That would put 50,000 dairy farmers out of business and significantly reduce the amount of agricultural land devoted to that industry.

According to the Department of Agriculture, there are nearly 2.3 billion acres of land in the United States. Four hundred and eight million acres of that is cropland, while pasture and rangeland totals 614 million acres. A 2014 study in the Proceedings of the National Academy of Sciences reports that 8 percent of pasture and range land was devoted to dairy cows, 13 percent to growing hay, and 24 percent to growing concentrated feeds like corn and soybeans. The USDA reports that in 2014, the soybeans and corn were each grown on about 84 million acres of land. Additionally, farmers grew hay and silage crops on 63 million acres for livestock feed. So if all dairy cows were eliminated that would mean that 40 million acres of cropland, 50 million acres of pastureland, and 8 million acres of hay land could revert to nature. That's nearly 100 million acres, about the size of California.

What if meat production could similarly be moved to the laboratory and grown in vats? In 2013, a burger grown in the University of Maastrich's cultured meat lab was taste-tested in London, but it did not receive rave reviews. The burger was composed of muscle cells taken from a cow and grown in a vat. By one estimate, the current price of cultured beef would be somewhere around $30 per pound. Ground beef is hovering around $4 per pound now. The startup Modern Meadow is working to produce cultured meat and leather. If cultured meat can be made cheaper than the on-the-hoof version, the effect on farming would be far-reaching, to say the least.

Today Americans eat about 25.5 billion pounds of beef annually, amounting to about 7 percent of the calories in an average diet. There are about 90 million beef cattle in the United States. A whopping 92 percent of pastureland, 87 percent of land used to grow hay and silage, and 21 percent of feed grains are used to grow beef cattle. If cultured beef entirely replaced the conventional kind that would mean that 35 million acres of cropland, 565 million acres of pastureland, and 55 million acres of land used to grow hay could revert to nature. That 655 million acres amounts to just over 1 million square miles of land, equal in size to all of the U.S. states east of the Mississippi River, plus California.

In a 2011 study, researchers from Oxford and the University of Amsterdam calculated that replacing farmed meat with cultured meat could cut energy use by 7 to 45 percent, greenhouse gas emissions by 78 to 96 percent, land use by 99 percent, and water use by 82 to 96 percent. While noting uncertainties, the researchers concluded that "the overall environmental impacts of cultured meat production are substantially lower than those of conventionally produced meat."

About 30 to 40 percent of a typical American diet consists of starches, usually derived from grains such as wheat and corn. Y.-H. Percival Zhang, a researcher at Virginia Tech, has developed an enzymatic technique that can turn indigestible cellulose into the digestible starch amylose. Growing a ton of grain typically involves producing two to three tons of cellulose in the form of leaves and stalks. Zhang's technique can transform any source of cellulose, including wood chips and weeds, into edible starch, feedstocks for bioplastics, and glucose for bioethanol production.

Zhang notes that a biorefinery using his enzymes could turn up to 50 percent of what would normally be agricultural waste into edible starch. Assume a cellulose-to-edible-grain ratio of two to one and a transformation rate of 50 percent. That would essentially mean that enough dietary starches could be grown on half the 140 million acres of cropland planted now in wheat and corn. Seventy million acres amount to 109,000 square miles, an area about the size of Colorado.

In the future, "factory farms" will be increasingly replaced by real factories. Still, there would be plenty of scope for niche markets offering "real" milk, steaks, and grains grown on handicraft farms.

The land sparing that these three technologies could make possible adds up to 208 million acres of cropland and essentially all of the 614 million acres of pastureland in the United States. Restoring even half that much acreage to nature would provide plenty of space for buffalo to roam again and pronghorn antelopes to play.

Correction: Originally wrote "million". Thanks Felix.