If we got rid of all cattle, we would not reduce the amount of soybeans grown by 77%, just our utilization of what is grown.
If anyone wants to engage with the consequences of animal agriculture, this is a great starting point: https://www.europarl.europa.eu/climatechange/doc/FAO%20repor...
What do you imagine we would do with the soy pucks that are produced after extruding the oil?
Also, ruminants need non starchy, fibrous plant materials. I can't speak toward chicken and pork but I don't advocate people eat those.
"86% of the global livestock feed intake is made of materials that are inedible by humans" - Sacred Cow, Diana Rogers, source: https://www.sciencedirect.com/science/article/pii/S221191241...
Of that last 14% of human edible food, the vast majority is used at the end to fatten up the animals for slaughter.
"Results estimate that livestock consume 6 billion tonnes of feed (dry matter) annually – including one third of global cereal production – of which 86% is made of materials that are currently not eaten by humans. In addition, soybean cakes, which production can be considered as main driver or land-use, represent 4% of the global livestock feed intake. Producing 1 kg of boneless meat requires an average of 2.8 kg human-edible feed in ruminant systems and 3.2 kg in monogastric systems. While livestock is estimated to use 2.5 billion ha of land, modest improvements in feed use efficiency can reduce further expansion."
Even the source you are citing agrees that after massaging the numbers as much as possible it's still 3x less efficient to produce calories for human consumption by feeling animals.
I cannot access the full article, but from the abstract that seems to not be congruent with what the study is suggest. Perhaps you are confusing kg for kcal? It could indeed be the fact that it is 3x less efficient by weight.
Given that the article is pointing out that 86% of the feed for animals is not edible by humans, claiming that meat is 3x less efficient calorie wise with these numbers is also making the claim that we are growing plants 2x more calorically dense by meat than weight.
Beans are the crop. Everything else must wait until they are ready, and by then it will be basically dry matter. Therefore all except the beans is a residual.
Can still be recycled into more human food by herbivores, but we couldn't do it directly. We can't feed on dry stems, withered flowers or brown leaves.
If you want specific studies I can go look up in the book but it sounds like your asking for further reading, not cited sources.