An industry once based on small, independent farms is evolving into large operations housing thousands of animals under one roof. The change is helping make beef, poultry and pork more affordable. But animal waste from the mega-farms has fouled waters.

By John Flesher, Associated Press

There's a large and growing movement across the heartland states to use big, intensified agriculture as a path to restoring soil life and a stable climate.

By Miriam Horn