Judy Woodruff: Now, before you gather for that holiday meal, our economics correspondent, Paul Solman, asks, what's the beef people have about beef? There have long been debates over the environmental effects of the meat industry and moral arguments made against killing animals. The rise in popularity of new meatless options adds a different dimension to the discussion. Paul examines the questions tonight. It's part of his weekly reporting for Making Sense.

Gov. Arnold Schwarzenegger: To avoid catastrophic climate change.

Paul Solman: Yup, ex-Governor, ex-Terminator Arnold Schwarzenegger in a video created to indict beef.

Gov. Arnold Schwarzenegger: Less meat, less heat, more life.

Paul Solman: So trending, beef is bad, as this new documentary luridly asserts.

Woman: When you consider the devastation it's having on our planet, as well as the oceans.

Paul Solman: No wonder the plant-based-meat start-ups profiled recently here on Making Sense want to chop meat from our diets, and the planet, entirely, and replace it with products like the Beyond Burger, or with Beyond's main rival, the Impossible Burger. Biochemist Pat Brown, CEO of Impossible Foods, wants to replace grazing animals entirely. By when?

Pat Brown: By 2035. The use of animals to produce food is the most destructive technology in use on Earth today.

Paul Solman: And here's the CEO of rival Beyond Meat.

Ethan Brown: You look at heart disease, diabetes and cancer, those things, there's a correlation between those things and the levels of meat and the type of meat that we're eating.

Paul Solman: Besides the argument against killing animals for food, the beef against beef features a trio of charges, bad for the land, bad for the air, bad for the body. Negative externalities, they're called in economics, costs that the price of the product doesn't include. So let's hear the case, one externality at a time, starting with lays waste to the land. Impossible's Pat Brown...

Pat Brown: We could produce all the protein required by the world's population in 2050 with 2 percent of Earth's land if we did it the way we're producing our meat, as opposed to more than 45 percent of Earth's land that's currently being used raising animals for food.

Paul Solman: Right, says his rival CEO, Ethan Brown.

Ethan Brown: We can get this right, and once we do it, we can liberate those fields. They don't have to be serving that really inefficient master. They can even start planning things directly there that are protein for human consumption.

Paul Solman: The mighty master steer, that is, so inefficient that:

Jonathan Foley: If you take the 30 calories of corn grown in Iowa and turn it into a hamburger, you're lucky to get one calorie of new beef that we actually eat.

Paul Solman: Jonathan Foley of the California Academy of Science.

Jonathan Foley: Well, cows and goats and sheep and things are in the brown areas.

Paul Solman: Foley has actually mapped the land use problem.

Jonathan Foley: This is showing the footprint of agriculture on the planet. What really surprises people sometimes is that 38 percent of all the land on Earth is covered in food. For example, all of this land 75 percent of it, all of those red areas and a lot of the green areas, are used to produce meat, either directly by grazing or by growing crops, so we then later feed to animals in a feed lot.

Paul Solman: In addition, says Jonathan Foley, growing beef consumption in the less developed world leads to deforestation, clearing the land for cattle. So, what says the defense? Look at this guy. Would they respond to me, or no?

Bill Niman: Anybody that would come out here in an outfit like that, I doubt that they would respond to someone like you.

Paul Solman: In Marin County, California, grass-fed guru Bill Niman and wife Nicolette, defender of beef.

Nicolette Niman: What's so miraculous about these animals is they're basically just taking the energy of the sunlight that's going into the vegetation, and they are converting it, with very little input from humans.

Paul Solman: Humans, who can't eat grass.

Bill Niman: These animals can convert cellulosic material to nutritious and delicious food for human consumption. And I don't think you can do that in a lab.

Paul Solman: Ag Professor Frank Mitloehner echoes the Nimans.

Frank Mitloehner: Here in California, half of all land in the state is marginal land, is rangeland used for cattle. And without them, you could not use that land for human food production. Two-thirds of all agricultural land in the world could not be used for food production for people.

Paul Solman: So removing grazing animals entirely would leave unfarmable acreage four times the size of California. But what about waste in water? It takes nearly 2,000 gallons to produce one pound of beef. Compare that to broccoli and cauliflower. The lowly legumes require just 34 gallons a pound. But, says Nicolette Niman...

Nicolette Niman: And so the whole ecosystem holds a lot more water in it when you have grazing animals, when they're well-managed. You also have just a lot more biological activity in the soil. And that turns out to be the cornerstone of sustainability for the whole food system.

Paul Solman: Biological activity enhanced, she says, by a very positive externality of cattle. That cow is pooping as we speak.

Nicolette Niman: Yay! Poop is good.

Paul Solman: Moreover, animals provide half our farm fertilizer. If poop goes, do bad-for-the-planet nitrates replace it? OK, but what about externality two, greenhouse gases? What percentage of greenhouse gases are accounted for, in your estimation, by livestock?

Jonathan Foley: Somewhere in the neighborhood 15 to 18 percent, yes.

Paul Solman: That's globally. Bovine bubble. So explain to me what this is?

Frank Mitloehner: So these are bovine bubbles that we use to measure the impact of livestock on the air.

Paul Solman: His measures, says Professor Mitloehner, show that emissions in America are much smaller than the global average.

Frank Mitloehner: Why? Because the efficiencies of livestock production in the United States have reduced our carbon footprint to historical levels. These heifers here will be finished, meaning go into slaughter, when they are 14 months of age. So, they're still very young. If they were on pasture their whole life, they would go to slaughter twice that age.

Paul Solman: If the rest of the world followed suit, Mitloehner says, the greenhouse effect would drop dramatically. But can it? Moreover, Jonathan Foley adds, American efficiency generates plenty of negative externalities itself.

Jonathan Foley: There's 100 million acres of corn that are basically being turned into cows. There's another 80 million acres of soy beans here.

Paul Solman: All right, that's land and air. What about bad for the body?

Walter Willett: We do see that higher amounts of red meat in the diet are associated with many adverse health outcomes.

Paul Solman: Harvard nutrition expert Walter Willett.

Walter Willett: Cardiovascular disease, more cancer, more diabetes, higher total mortality.

Paul Solman: Adds food advocate Anna Lappe...

Anna Lappe: And right now in the United States, we consume basically twice as much, on average, protein as our bodies need.

Paul Solman: Impossible Foods' technology raises another concern. The FDA asked the company to re-test a key ingredient, soy leghemoglobin, to make sure it isn't an allergen. But, hey, it's about time for the final verdict. Who better to reach it, I thought, than "Omnivore's Dilemma" author Michael Pollan, who famously chronicled the foreshortened life of Number 534, a steer he bought and tracked from birth to feed lot to slaughter.

Michael Pollan: I think meat is a delicious food that humans have been eating for a very, very long time, and I think there is a place for animals in sustainable agriculture. However, that's not the kind of meat we're eating now. We're eating the products of a wasteful and polluting feed lot system, and that allows us to eat an unnaturally large amount of meat.

Paul Solman: Should plant-based meat replace meat-on-the-hoof completely?

Michael Pollan: The realistic goal is not to destroy the meat industry. People are going to continue to eat meat. It's to shrink it. It's to bring it back to a scale where we can raise cattle without destroying the environment.

Paul Solman: And it turns out even the Nimans aren't telling us to gorge on their never-seen-a-feed-lot friends. And, finally, what about plant-based meat?

Nicolette Niman: When you're taking something in the diet that is simple and nourishing as eggs, meat, and milk, and you're telling people, you should replace it with this thing I created in a laboratory, I don't think it's going to work.

Paul Solman: I guess we will see. For the PBS NewsHour, this is economics correspondent Paul Solman. Come cattle! Let's come! Trying to call the cows, while reporting from California.