“You wouldn't be able to feed all the people on Earth”

    (This answer coincides with the helping other humans question.)
    Diet for a Small Planet author Frances Moore Lappe writes,
    “Imagine sitting down to an eight-ounce steak...then imagine the
    room filled with 45-50 people with empty bowls in front of them. For
    the ‘feed cost’ of your steak, each of their bowls could be filled with
    a full cup of cooked cereal grains.”

    (We feed TONS of edible grain to farm animals to produce small
    amounts of food for and this greatly contributes to world famine.)