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Workers harvest soy on a farm in Bahia, Brazil. Paulo Whitaker/Reuters

With food prices hitting record highs, people are rioting and political regimes are crumbling. We can only imagine what it will be like when the global population rises to 9 billion in 2050 from just under 7 billion now. More riots, more deforestation, more hunger, more revolutions? How are these people going to be fed? The unequivocal answer we so often hear: biotechnology.

Let's ignore for the moment the cause of rising food prices, which have been attributed to everything from bad weather and poor harvests to higher oil prices that push up the cost of fertilizers, the rise of biofuels, even commodity index funds (which are bidding up futures, though I'm skeptical they are leading the parade). The thing I get hung up on is the "9 billion." It makes a great sound bite but what's behind the figure?

So far the vast resources of commercial biotechnology have gone to commodity crops such as corn and soybeans (and soon alfalfa). The majority ends up as animal feed, and thus meat, which is the least efficient way to produce calories. Meat also happens to be available to the richest people, not the poorest. So, we haven't really used genetically modified organisms (GMOs) to "feed the world." Instead we've used them bring down the cost of industrial meat production and incentivize a transition to a meat-centric diet. The loss of calories that result from feeding grains to animals instead of humans represents the annual calorie needs of more than 3.5 billion people, according to the UN Environmental Program. In short, GMOs arguably are making matters worse by fueling the production of more animal feed and food-competing biofuels.

Be that as it may, we're still stuck with the 9 billion problem. Population is like compounding interest, with small changes producing big results down the road. So the growth rate is hugely important and it doesn't always do what's expected. National Geographic had an interesting take on this, showing that the argument popular in the 1960s about a "population bomb" largely turned out to be a fiction. By the early 1970s, fertility rates around the world had begun dropping faster than anyone had anticipated. Since then, the population growth rate has fallen by more than 40 percent:

In industrialized countries it took generations for fertility to fall to the replacement level or below. As that same transition takes place in the rest of the world, what has astonished demographers is how much faster it is happening there. ... "The problem has become a bit passé," Hervé Le Bras (a French demographer) says. Demographers are generally confident that by the second half of this century we will be ending one unique era in history--the population explosion--and entering another, in which population will level out or even fall.

This is why numbers are important. On that score, Andrew Revkin had an interesting exchange on the Dot Earth blog at the Times that showed a range of opinion on what it would take to "feed the world." Revkin's post noted that Douglas Southgate, an agricultural economist at Ohio State University, "argues that a low growth scenario for population, leading to just under 8 billion people by 2050, could see a 26-percent drop in food prices even with substantial rise in consumption." This is considered the low-range for 2050, but considering how off the mark Malthusians were in the past, it shouldn't be entirely discounted.

But let's say we do get to 9 billion. The impact on resources, it turns out, depends a lot on what we eat. Vaclav Smil, a University of Manitoba analyst, pointed out to Revkin "a menu of possible food lifestyles," which for a world of 9 billion meant either bountiful supplies or scarcity. Here's the spectrum:

1) eating enough to survive with reduced lifespans (Ethiopia), 2) eating enough to have some sensible though limited choices and to live near-full lifespans when considering other (hygienic, health care) circumstances (as in the better parts of India today), 3) having more than enough of overall food energy but still a limited choice of plant foods and only a healthy minimum of animal foods and live close to or just past 70 (China of the late 1980s and 1990s), 4) not wanting more carbohydrates and shifting more crop production and imports to [livestock] feed, not food, to eat more animals products, having overall some 3,000 kcal/capita a day and living full spans (China now), 5) having gross surpluses of everything, total supply at 3,500-3,700 kcal/day, eating too much animal protein, wasting 35-40% of all food, living record life spans, getting sick (U.S. and E.U. today).

Obviously, we want to avoid option one and two, as much as possible. Option three and four would mean 1 billion people who lack enough food today would be better off. But Smil says, "The world eating between levels 3-4 would not know what to do with today's food." In other words, we have enough already. But, he also adds, "the world at 5 is impossible." Nor is it desirable, considering the obesity crisis and health risks.

So really, the question isn't how will we feed 9 billion by 2050? The question is how many people will we really have and what will they be eating?

Poverty of course plays a big role in both these issues because, as Juergen Voegele, director, agriculture and rural development, the World Bank, pointed out to Revkin: "We already have close to one billion people who go hungry today, not because there is not enough food in the world but because they cannot afford to buy it."

Raising incomes, or course, is a difficult nut -- one that doesn't succumb to a solution hatched in a lab. But more income means better-educated families, and even declining population growth. The flip side, though, is that rising incomes are also associated with higher meat consumption, which can get us closer to option five on Smil's lifestyle if we are not careful. So the best case: to raise incomes and to incentivize less resource-intensive food consumption.

But we don't need to become vegans to save the world (which would doom us even if we did because so few would go along). In many developing countries, such an approach would amount to culinary imperialism, given the importance of meat for both income generation, the result of having a cow or goat or two, and as a source of much-needed calories for children from milk and scant meat. Never mind the use of manure to grow crops. We're not talking about factory farms here, but animals that play a central role in cultures and livelihoods.

As the Nat Geo article concluded: