OK, I'll go back on my title for this article: Sustainable meat production (in terms of environmental impact) is possible—but only for the very few. I meet people quite often—well-meaning, thoughful, caring and vigilant about their meat consumption, who insist that if we grass-fed all the beef, if we free-ranged all the chickens, the world would be a better, cleaner place, we would all be healthier, and everyone could still eat meat too — yay! 

And if we had an unlimited world, with unlimited amounts of grain and pasture and space, this could work. But we don't. We have one planet Earth and currently 7 billion people on it. And we keep eating more and more meat. And making more and more people. According to the Worldwatch Institute, "Per-capita meat consumption has more than doubled in the past half-century, even as global population has continued to increase. As a result, the overall demand for meat has increased five-fold." World meat consumption is expected to double by 2050. Already, according to the New York Times, "an estimated 30 percent of the earth’s ice-free land is directly or indirectly involved in livestock production, according to the United Nation’s Food and Agriculture Organization, which also estimates that livestock production generates nearly a fifth of the world’s greenhouse gases — more than transportation." 

With meat consumption rising, those who produce beef, chicken, pork and other meats have to be as efficient as possible—and that is not free-range animals living on a bucolic farm. There is only so much space that's suitable for raising livestock in a lower-impact, healthier-for-the-environment (and the animal) way. Packing them into feedlots, feeding them grains (instead of grasses for cows and bugs and worms for chickens) is cheaper, faster and easier. 

With more people, should we be throwing away calories towards meat production? It's seems unethical, since for every 100 calories of grains and feed we give to a beef cow, we only get 20% back in edible calories—and that's if we don't waste a bit of meat. It's slightly better for chickens, which give us 25% of calories fed back, but worse for pigs, at 15%. What this means is that there is competition between feeding people and animals to feed people. It's just plain inefficient; if we want more people we have to eat less meat. And that grain production doesn't just use calories that could go to feed people instead of animals. The New York Times reports, "The environmental impact of growing so much grain for animal feed is profound. Agriculture in the United States — much of which now serves the demand for meat — contributes to nearly three-quarters of all water-quality problems in the nation’s rivers and streams, according to the Environmental Protection Agency." And we know that fresh water resources are threatened as climate change heats up and as more people need it to drink and bathe with.  

But, "There must be a way!" you think. "I want to eat meat and not contribute to environmental or human destruction!" Sure there is. 

Here's how we can keep up America's current consumption of meat and expand it to the rest of the developing world: 

Massively limit population growth: Meat production was sustainable for milennia, since there were many, many fewer people on earth, the waste and emissions that animals produced weren't impactful enough to be a problem. We can all eat meat every day if there are as many people as there were on the planet in, say, 1927 when there were about 1.2 billion people on the planet. Or hey, we can even stretch it to 1950 (that golden age of hamburgers), when there were just 2.5 billion people, almost 1/3 the number there are today. Now we just have to figure out how to wipe out 2/3 of the world population so we can all eat meat! Ideas?  

The question is—more people, or more meat? We can't have both. 

Embrace lab-grown meats: Many people are disgusted by the idea of in-vitro meats, but if you want to eat some animal flesh, well, this is a low-impact way to get your meat fix on. As MNN writer Robin Shreeves detailed, "A 2011 study in the journal Environmental Science and Technology, for example, showed that full-scale production of cultured meat could greatly reduce water, land and energy use, and emissions of methane and other greenhouse gases, compared with conventional raising and slaughtering of cattle or other livestock."

I don't see any other alternatives, do you? Of course, we could ALL eat less meat (a couple times a week, maybe), which would then make well-raised meat possible for all because meat consumption would be much lower overall. Or half of us could go vegetarian (most of us who are love it!). But I don't see that happening—unless of course, the very last option, which I think is the most likely, comes to pass—meat becomes prohibitively expensive, a wealthy person's food, a daily treat for the 1% only—you know, how it was for basically all of human history around the planet until the current industrial era. 

Related on MNN: 
Laboratory-grown meat is one stop closer to reality

Vegetarian for 20 years: Logistics and tools

9 superstar athletes who don't eat meat

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.