There are 37 billion acres of land on planet Earth, and 37% of them -- nearly 14 billion acres, an area larger than Asia -- are devoted to agriculture.
There are 7.6 billion people on the planet, and demographers say there will be 9.7 billion by 2050.
And there is a continuing debate over the best use of the planet's land to feed those 2 billion additional mouths. One possibility is to boost the productivity of those 14 billion acres. Another is to put more acres into agricultural production. A third is some combination of the first two.
The public has heard a lot about the possible downsides of intensifying production on existing land. Commercial agriculture's critics say it will mean more overuse of chemicals, nutrient runoff, destruction of biodiversity, and long-term depletion of soil health.
Until recently, the public has heard less about the downsides of adding ag acreage. But that's starting to change.
An obvious downside that doesn't get stated often enough is the limited supply of land. Assuming no increase in ag productivity and diets similar to today's, agriculture would have to add 4 billion acres to accommodate those 2 billion additional mouths. Good luck finding that many acres. Of the current 23 billion non-ag acres, 21 billion are mountains or desert.
Now, to be sure, animals can graze and plants can thrive on mountainsides; in Bhutan three years ago, I saw terraced rice fields 8,000 feet above sea level in the foothills of the Himalayas. Deserts can be cultivated, as well. Arizona raises a lot of cattle and grows a lot of lettuce, cotton and hay.
But much of this mountain and desert agriculture has low yields, and its ability to expand is constrained. The New York Times Magazine provided a reminder of those constraints in a story from Arizona's Sulphur Springs Valley, where the water level in the aquifer dropped 100 to 300 feet in 35 years. (https://www.nytimes.com/… )
Many homeowners in this valley have dry wells and can't afford to drill deeper. Yet farming companies from Saudi Arabia and the United Arab Emirates have acquired tens of thousands of acres of land to grow alfalfa, dairies are expanding, and almond growers from California are moving in.
Desalination and other technologies may make farming possible in places where it hasn't been, but it's doubtful the world can rely heavily on mountain and desert land to provide the food for its rapidly expanding population.
Even if the planet had 4 billion acres to spare, a growing body of research says repurposing them for agriculture would hurt the environment. In a recent study of agriculture in Ghana, Mexico and Poland, scholars found halting agricultural expansion is critical to storing carbon so it doesn't escape and warm the atmosphere. (https://www.sciencedaily.com/… )
"We were a bit surprised by just how consistent and how strong the result was," one of the scholars told Science Daily. "The three systems we investigated are very different both in terms of the natural habitats and the farming systems, but in each case it was clear that land sparing -- combining high-yield agriculture with preserving or restoring natural habitats -- consistently had the potential to store greater amounts of carbon than any other system."
A National Geographic survey a few years ago came to a similar conclusion. The magazine's scientists outlined a five-step plan for feeding the world while saving the environment. The first two steps were "Freeze Agriculture's Footprint" and "Grow More on Farms We've Got".
If, as these studies suggest, agriculture's footprint is to be frozen, existing farmland will have to produce a lot more food -- and produce it with minimal damage to the environment. That won't be easy, but there are reasons for optimism.
Technology marches on. Precision agriculture is already helping farmers get higher yields with less fertilizer and the more it's used the better it will get. Seeds keep improving. And scientists are at work on things that until recently would have been dreams -- crops that make better use of sunlight, cows that emit less methane, new methods of recycling nutrients. If society is willing to fund the research and keep an open mind about changes in how food is grown, farmers may well be able to feed a 10-billion-person planet.
Urban Lehner can be reached at email@example.com
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