I want to compare the import of animals as food (meat, fish, egg, cheese, butter, animal fat and oil etc) with the other import of animals in ensuring a sustainable human life. Which is greater to human's sustainability, the nutritional value of animals or their other value?
Given a hypothetical situation where no human ate any animal foods that are important in our nutrition today, but rather ate only plant-based foods, leaving all animals to serve their other purposes in life, would humans experience a better or a worse sustainable human life (if all other ecological circumstances remain the same)?
What is your expert opinion and source of reliable data?