On to Land, Part One: Feed Me

If we’ve got usable water, which is far from a given, then we can take the next step and figure out how much land is necessary to grow plants and livestock to feed a single person.

I hope most who stumble onto this site will stick with the more detailed explanation, but if you’re an impatient sort, click for a quick presentation by the American Farmland Trust. If you think we have plenty of land on which to grow food, this should disabuse you of that opinion.

If you have time and patience, then wade on to land with me, starting with a recap of the water situation and the world’s water/land ratio.

The earth is roughly 70% water, but only 2.5% of that is drinkable or useful for irrigation. Of that paltry 2.5%, something like 2/3rds is frozen into glaciers. What’s left for use in farming and everything else people do comes mostly from aquifers, underground water and wellsprings—sources that people are depleting rapidly.

The info above comes from Charts Bin, “Surface Area of the Earth.”

(In case you missed them, my posts of 15 Feb. 2010 “When the Well Is Dry, We Know the Worth of Water” and 17 Feb. 2010 “When the Well Is Dry, Part 2” are on water.)

Now on to land. Charts Bin also breaks land into categories:

• The percentages of earth’s land surface can be divided into different types: 20% covered by snow land, 20% mountains, 20% dry land, 30% good land that can be farmed [emphasis added], 10% land doesn’t have topsoil.

Like most reliable sites, this one has a good list of sources appended, including the redoubtable CIA World Fact Book. Many other sites, such as PhysicalGeography.net, provide similar information.


The world is 30% land, and 30% of that is arable. My calculator tells me we have 9% of the world’s surface that’s suitable for farming—and not necessarily top class farming, but now we’re closer to an actual discussion of soil.

However, before that happens, we all need to know some important concepts. And they all involve numbers. {evil laugh} I know that for most people—me included—numbers aren’t enticing, but they are crucial.

I’ve heard too many people toss off figures to show how we have nothing to worry about based on vague or inappropriate starting points. For example, I’ve heard we have nothing to worry about as far as population or pollution because people occupy only one percent of the world’s surface.

What’s that mean? Total surface? Dry surface? Arable surface? Desert, polar, mountaintop? Big differences. So clear, contextualized facts are crucial here.

Since much of the info I found deals with measurements most of the rest of the world uses, here’s a quick set of conversions:

One square kilometer equals 0.3861022 square miles.

One square kilometer equals 100 hectares.

One hectare equals 2.471044 acres.
(For here, saying a hectare is 2.5 acres will do.)

For years, I’ve used Josh Madison’s measurement conversion software Convert It’s for Windows and it’s free. If you’re on a Mac, I hope you can find something similar.

OK. Now on to the meat and potatoes, so to speak.


This sounds like a simple question, but it’s not. First of all, not all arable land is created equal. How deep is the topsoil? How rich is the topsoil? Is the soil level and easily worked? Terraced? How much precipitation does the land receive? Is irrigation water available? How long’s the growing season? Is there a salinity problem with the water supply? On and on and on. Since arable land also includes growing crops for livestock to eat, the questions continue. Is the land irrigated or dryland? What livestock? Chickens? Goats? Cattle? What?

As usual, the closer one looks at a problem, the more complicated and complex it becomes. In searching for answers on how much land it takes to feed one person, I’ve found answers ranging as low as a thousand square feet for a sparse vegetable diet, sometimes called a recipe for slow starvation. Of course, this tiny figure assumes intensive gardening by a master gardener with everything needed readily available and going the right way, every day.

As someone with a little farm and garden experience, let me just say this: Never count on things going right.

I’ve grown personal vegetable gardens ranging from 2500 square feet down to about 120 square feet, and I can tell you that some years I get more off the 120 square feet of raised beds than I did off the bigger garden. I can also tell you farmers live in apprehension. Last summer, when a hail storm turned my flourishing little garden into goo, I flashed back to a family story about my usually stoic Swedish grandfather sobbing as he watched a sudden storm flatten his harvest-ready eighty acres.

Storms and other disasters aside, we need a starting point for amount of land. Here’s one rough guide to how much land a person needs from the website AskMetafilter:

Each person needs —
vegan food — 3000 sq. ft.
a few eggs/week — 3,500 sq. ft.
one chicken/week — 24,300 sq. ft.
one cow/year — 67,300 sq. ft.

Whether this factors in hail storms, cows that bloat and die, and coyotes that find the flaw in the fence and eat all the chickens, I don’t know, but I’m dubious of even the 67,300 square feet. That’s only a little over an acre and a half.

A typical acre and a half in Colorado isn’t going to support anyone wanting a considerable amount of meat. On the other hand, it would where I grew up in Western Washington.

Considering the variables, I’m a bit more comfortable with the amount of land suggested in “Sustainability of Land Use and Food Production,” written by a member of the Toronto Vegetarian Association:

At Toronto’s Royal Agricultural Winter Fair in 1992, a display presented two contrasting statistics: It takes four football fields of land (about 1.6 hectares) to feed each Canadian and One apple tree produces enough fruit to make 320 pies. If you think about it – a couple of apple trees and a few rows of wheat could produce enough food for one person on a mere fraction of a hectare!

Notice that the author cleverly says “fruit” for these pies, not ingredients? Where’s the sugar and flour coming from? Not so easy figuring all this out, is it?

Then too, most of us in North America are not vegetarians. I suspect many more of us will become so over the next few decades, willingly or not, but for now, it’s reasonable to assume that most of us are still omnivores. To me, that means we’ll need land on the higher end of the range.

Joel E. Cohen’s 1996 How Many People Can the Earth Support? has “Eight Estimates of human Carrying Capacity.

All these are imprecise, imperfect, merely working models. They will, however, provide you with tools for more accurate guesses. Welcome to science!

I’m now moving on to another aspect. Is our food production capacity stable, going up, going down?



3 Responses to “On to Land, Part One: Feed Me”

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