I'm highly dubious of the statement that growing plants to eat them is lightly less polluting than growing plants, feeding them to cattle and then preparing the cattle to eat the meat. Cattle does not sequester CO2 like plants do and emits greenhouse gases. Also uses way more treated water.
When cattle are raised on well managed pasture, there is zero transportation between the cattle and feed, where as all vegetables requires transportation, and more of it pound-per-pound to reach the nutrient value of beef.
Cattle only contribute GHG when raised on grain as their digestive systems creates excessive methane breaking down corn. If more people understood how cows and ruminants should work vs how they are currently used in the industrialized feed complexes, they'd realize cows are not the problem, it's how we are using them.
Right, but cattle can be raised where growing plants is impossible, and they can be fed by-products of plant agriculture that is not fit for human consumption.
It's really not an either-or, something that I feel is often lost in these discussions. Eating plants and meat is complementary, and has been for all of human history.
It's also becoming possible to grow plants hydroponically in a highly automated and controlled environment (warehouse/cattle shed), with up to a 98% saving in treated water usage, 60% less nutrients required but with more nutritious crops and no pesticides. This is the case for High Pressure Aeroponics, which is slightly more complex than other hydroponic methods.