Journalist Emily Brady, a native of Tomales, spent more than a year living in Humboldt County researching her new book, Humboldt: Life on America’s Marijuana Frontier. The region became an epicenter of marijuana cultivation after an exodus from the Bay Area in the 1960’s by back-to-the-landers who found that the plant provided them with a steady source of income. Ms. Brady’s book follows four individuals who represent different facets of the area’s economy and…