This essay is excerpted from The New Economy of Nature: The Quest to Make Conservation Profitable. In a cattle pasture south of downtown Napa, Calif., a clarinet, flute, and bass guitar strike up a jazzy version of "Up a Lazy River." About sixty people, if you count the rubberneckers wandering over from a nearby retirement house, gather in the midsummer sun. Two young women in flowing dresses open paper boxes to release orange clouds of monarch butterflies. A few dogs wander through the crowd. The Napa River. Photo: City of Napa. It's a markedly mellower scene than your average U.S. …