⚡Trophic Levels

In order to eat animal products, first an animal must be bred and raised. All of this requires energy, and that energy comes from feeding these animals plants, typically grown in crops. This is well understood in the animal agriculture industry and there exists what is called a food conversion ratio (FCR) to describe how many plant calories are required to produce one calorie in an animal product. It is always less efficient to produce and eat animal products than to eat plants directly. This is because of basic laws of thermodynamics:

1. Energy cannot be created or destroyed, only transferred

2. Whenever energy is transferred, there is inefficiency

The trophic pyramid is how nature is affected by these laws. Most of the energy on earth comes from the sun, which phytoplankton and plants (primary producers) capture via photosynthesis and store as carbohydrates, fats, and proteins - this is a transfer of energy. Herbivores and omnivores (primary consumers) consume some of those plants and algae (resulting in a further in a transfer of energy), and carnivores (secondary consumers) consume some of those herbivores and omnivores (resulting in a further transfer of energy), and so on. Every time energy is transferred via one lifeform consuming another, as a rule of thumb, 90% of the energy is lost as heat. The energy isn't destroyed, but it is unable to be converted into a form the organism can use as nothing is completely efficient. Animals use up energy walking around, heating their bodies, etc., so only ~10% of the energy makes it up to the next level on the pyramid. So we as humans, if we consume animal products, end up as secondary consumers - meaning we only receive ~0.1% of the energy that was originally supplied by the sun. Whereas if we consume plants directly we are generally 10x as energy efficient and receive ~10% of the energy originally supplied by the sun. This means that fewer plants are killed by eating plants directly, and less land and resources are required to sustain ourselves. This is better for the environment, which is ultimately better for humans and other animals.

Leaving the realm of hypotheticals and rules of thumbs, we can see that the practical data supports this. "The US Department of Agricultural Economic Research Service puts the figure at 16 kg of grain to produce 1 kg of beef." https://awellfedworld.org/wp-content/uploads/pdf/CIWF%20Eat%20Less%20Meat.pdf Stanford Mag published a figure of 20 pounds of grain to produce 1 pound of beef. https://stanfordmag.org/contents/can-vegetarianism-save-the-world-nitty-gritty Of course, organizations with conflicts of interest against the truth tend to skew the data to attempt to claim more efficient FCRs than exist in reality. This is done by, for example, excluding some of the feed in the calculations.