[MikeHolman]

Beef is an extremely carbon inefficient source of calories. They require a large amount of land, either directly or indirectly (e.g. from corn fields). Pastures and farmland are not effective carbon sinks. Most land used by cattle was earlier forestland or other land that served as a carbon sink. For example, one of the major causes of rainforest destruction in Brazil is cattle ranching.

[ravenstine]

You know what's actually "calorie" inefficient? Eating leaves. Because that's exactly what humans are poor at and animals like cows are very good at (though technically they're digesting the bacteria that eat the predigested vegetation).

Plants are largely composed of cellulose, which is not digestible by humans. Just because we pass it through and just because a study found trace amounts of cellulose-consuming bacteria in our gut doesn't mean we are well developed to handle cellulose. Those are "calories" we are pooping out.

If you were to just look at the carbohydrate content of plants, well, if we reductively look at the energy density of macronutrients, sorry, carbs of any kind are not as energy dense as the fats from meat.

As an aside, this is one chief reason why calories, which are a measure of heat, are a poor metric for nutrition.

> Pastures and farmland are not effective carbon sinks.

Neither is any kind of farmland, whether it's cows that are being raised or tomatoes.

Carbon sinks only mean something in the case of fossil carbon being introduced to the atmospheric carbon cycle, but that doesn't matter anyway because no amount of trees added to the earth are going to offset anthroprogenic climate change in any appreciable way.

> Most land used by cattle was earlier forestland or other land that served as a carbon sink.

Not all forest land is a carbon sink, and not all forest land is woodland.

Also, I would really appreciate some evidence for this.

> For example, one of the major causes of rainforest destruction in Brazil is cattle ranching.

As if demolishing the Amazon is a prerequisite to cattle ranching, as opposed to something people do because the economic incentives are there, which has nothing to do with whether raising cattle in and of itself is harmful to the climate. Tons of beef are is raised on the Great Plains and has been for over a century, and the Great Plains is nothing close to the kind of carbon sink you're thinking of.

[ericd]

As a sibling commenter alludes to, should we ban lettuce?

Trying to tackle sources one by one is going to be a mess and give us a crap solution full of holes, and tons of argument and inaction as people fight for their preferred solutions.

Tax the carbon entering the carbon cycle and let the costs of that flow through all the supply chains, soften the blow for people via rebates and by ramping the amount up over time to a well-telegraphed future target, and things will adjust. The poor will generally come out ahead after the rebate, since they tend to generate a lot less carbon, the rich will pay much more. Things like flying will probably triple in price, or more, if we set it at the price for durable sequestration, and so people will fly much less for recreation. And maybe we'll survive as a species to see another couple generations.

[MikeHolman]

The point is that it is much more land efficient for us to directly eat plants than to route the plants through animals first. Cattle use 99% of the calories we feed them for their own functioning. Only 1% actually make it into the meat that we eat.

I wasn't proposing any specific solution, just stating that eating animals does in fact contribute more CO2 than eating plants. And I have no problem with carbon taxes, in fact I'm in favor. A carbon tax could certainly cover this case if it taxes the CO2 that animals emit.