A large portion of US corn production goes to feed beef cattle. About 40% for ethanol production and 40% as animal feed. It is also fed to hogs, chicken and other livestock. Corn is grown on about 95 million acres annually.I've heard that we're actually using more land than we would otherwise because a large portion of our crops goes to feed the cattle whose meat and milk we eat. But I defer to scientists on the question.
I am not arguing against the eating of meat, but those are some of the broad facts associated with corn production.
I would be interested to know about the claim regarding the quantity of land available for plant production. What I do know is that organic production could not feed the world population on the land we have available, but what is termed conventional agriculture can. In fact, the amount of production from conventional agriculture is increasing as the area of land necessary for that production is being reduced.