Most of horses’ land consumption comes from energy production (pasture), while cars’ production, storage, and maintenance contribute non-negligibly to their physical footprint, partly b/c the land cost of their energy is so low. The actual footprint of the Diablo Canyon nuclear plant dramatically undercounts the land surface area required by the cars it might power.

I countered that horses have their own unique land requirements. Just as cars need parking and junkyards, horses need stables and manure disposal services. And while producing horses doesn’t require building factories, it does entail feeding a mostly useless young animal for a few years.1 But Toby is right that cars need more land than what we use to power them. They just don’t need that much.

Let’s take a look at global land use statistics. The Food and Agriculture Organization of the United Nations has a nice land use dataset based on satellite images from NASA and the European Space Agency. At the ever-helpful website Our World in Data, Hannah Ritchie and Max Roser simplified the FAO data into this pretty visualization. 

You can see that agriculture takes up huge tracts of land—the equivalent of the Americas plus a large part of Asia—while our cities, towns, and roads (and anything else classified as an “artificial surface” by the FAO) have a footprint the size of Libya—just one percent of global land area.

These figures surprised me when I first saw them since I, like most people in wealthy industrial nations, spend almost all my time within that small purple zone. Living most of our lives within built-up areas screws up our perception of the environment. Since we’re rarely ever more than a few feet from a road or parking lot, we might assume, for example, that “we paved paradise” is an apt metaphor for what’s happened to the planet over the last few centuries. The reality is closer to “we plowed paradise.”

National data is more detailed, so let’s zoom in to the United States. Every few years, the United States Department of Agriculture produces a comprehensive review of U.S. land use based on satellite images, censuses, and on-the-ground surveys from other government agencies.

Like the world as a whole, the U.S. is dominated by agriculture, with urban areas and infrastructure taking up a relatively small amount of land. However, the USDA data leaves us with an annoying “other land” category, which includes some rural residential areas, as well as mines and quarries. To complete the picture, we can supplement the USDA report with American Housing Survey data on rural residential areas, an estimate of land used for the energy system from Bloomberg,2 and this comprehensive report on land used for mining based on satellite images.

Keep in mind that much of this research overlaps with USDA classifications. For example, rural residential land can include some cropland, pasture, and forest, and lots of our energy infrastructure lies within urban areas and national defense and industrial areas.3 That means we shouldn’t add these up. If we did, we’d get a significant overestimate of 262 million acres, or 11.6 percent of total U.S. land area (7 percent if we exclude rural residential land, likely the largest source of error).4

It might also be surprising that the U.S. uses so little land for mining, and you might suspect that we’ve offshored our mining footprint. That is partly true—the U.S. is a net importer of minerals—but we remain a top mining nation. The countries that mine the most land are Russia, China, and Australia, which use 2.9 million, 2.6 million, and 2.1 million acres, respectively. The United States takes fourth place with just over 2 million acres. Humanity as a whole uses just 0.07 percent of the Earth’s land for mining.

So, our towns, cities, roads, and other hard infrastructure take up a relatively small amount of land, especially when compared to agriculture. And, as with cars and horses, the reason is energy density.

While our total energy consumption has massively increased since the Industrial Revolution, almost all of that growth was supplied by fossil fuels, which, since they are highly energy-dense and come from underground, don’t take up much land. Agriculture creates a different form of energy: food, which is very land-intensive (recall that we use over a third of the Earth’s land for farming). Humans need food. And historically, we needed horses and other beasts of burden, which also need food. Now we approach a general principle: when we replace things that eat with things that don’t, we save land. That is also why one of the best things you can do for the environment is to eat less meat.

So, Toby, we should have a blinkered focus on energy production because the vast majority of humanity’s land footprint comes from producing energy in the form of food.

And Geoffrey, if you’re reading this, I hope it makes you less angry with me.

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Two years ago, I bought my parents a trail cam for their house in Vermont. We set it up on the edge of the forest, where it snaps photos at the slightest movement. So far, it’s spotted countless deer, squirrels, chipmunks, and raccoons, a few foxes, an opossum, a woodchuck, a bear, and a bobcat. These are lush woods. After a heavy summer rain, the dark parts grow thick with gnats and mosquitos, and all kinds of mushrooms pop up from the leaf litter. Certain places crawl with so many newts that you have to watch every step to avoid crushing them.

When fleeing from the bugs, it’s not unusual to come across an old mossy stone wall, leftover from a time when Vermont, and the rest of New England, was mostly field and pasture. The common story is that, in the mid-19^th century, farmers went west for flatter, richer land, or to the cities to work in new industries. The railroad brought cheaper produce back east, and New England’s farms were reclaimed by tenacious pine, cedar, and birch. It’s a true story, but not the whole story. Another part involves the automobile.

Before we had cars, we relied on horses and mules. Millions of them. In cities, they carried riders, delivered goods, and pulled cabs, wagons, omnibuses, and fire engines. On farms, they cleared land, plowed fields, and turned mills. As America’s cities rapidly expanded, so too did their stables and those of the farmers that fed them.

Horse populations were growing so rapidly that, even as most agriculture moved West, New England’s hay fields stuck around. Between 1880 and 1909, total cleared farmland in New England fell by almost half, from 13 million acres to 7 million, while land used for hay production fell just 11 percent, from 4.2 million acres to 3.7.1 This was mostly because hay has a relatively low value for its volume, making it less economical to transport long distances than something like grain. As long as there were horses in New England’s cities, much of their hay would be grown locally.

Horses began to decline in the early 20^th century as cars and trucks (and, to some extent, electric streetcars) replaced the legions of draft and riding horses in cities. Farm horses were gradually superseded by tractors and trucks but persisted in large numbers until mid-century.

As Anne Green writes in Horses at Work, “Horse populations dropped off from east to west. After 1910 the states with the largest horse populations were all west of the Mississippi.” By 1949, there were just over 2 million acres of hayfields left in New England, and by 2017, fewer than 1 million.

From a conservationist’s perspective, cars beat horses because of energy density. A well-worked draft horse could eat 30,000 calories of hay and oats each day, or the output of four acres of fertile 1930s cropland. A modern delivery van driving 100 miles a day (doing the work of multiple teams of horses) might consume 10 gallons of diesel fuel, refined from a tiny fraction of a typical oil well’s daily production. Each gallon of diesel contains around 35,000 calories (if only horses could digest it) and comes from underground reservoirs, leaving the surface mostly untouched.

Cars also don’t have to be kept alive. An idle horse needs 10 to 15 thousand calories per day just to keep breathing; an undriven car needs none. Electric vehicles have the potential to spare even more land. With a footprint of 12 acres—enough land for just three horses—California’s Diablo Canyon nuclear power plant can power over 4 million Teslas driving forty miles a day (roughly the American average).2

Back in the 1930s, lamenting the horse’s decline and its economic effect on farmers, the Horse Association of America extrapolated from the 1900 horse-human ratio and calculated that 54 million acres of U.S. farmland had been spared by the automobile. The country’s population has nearly tripled since then, and we live much richer lives. If our cities were fed by horse plow and our packages delivered by horse cart, hundreds of millions of acres of our forests would now be meadow.

My parents don’t live in the deep wilderness, but the houses are far enough apart that you won’t see the neighbors unless you go out looking for them. At night, the only reminder of the rest of humanity is the occasional flash of headlights through the trees. Those lights often frustrate me, breaking my sense of solitude amidst wild nature. But that feeling is entirely an illusion. The forests of New England sprung from modern civilization and its great symbol, the car.

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