When a livestock farmer is willing to "practice complexity"-to choreograph the symbiosis of several different animals, each of which has been allowed to behave and eat as it evolved to-he will find he has little need for machinery, fertilizer, and, most strikingly, chemicals. He finds he has no sanitation problem or any of the diseases that result from raising a single animal in a crowded monoculture and then feeding it things it wasn't designed to eat. This is perhaps the greatest efficiency of a farm treated as a biological system: health.