Dell Emerson sat watching a conveyor belt run at Wescogus Wild Blueberry on Thursday. All around him was evidence of a lifetime growing not just blueberries, but the state’s wild blueberry industry. About 20% of the state’s blueberry land has gone out of production in the last five years, according to the Maine Wild Blueberry Commission industry group. Emerson also helped start a wild blueberry growers cooperative that sells fresh berries in the 1980s. In 2001, the couple opened Wild Blueberry Land, more recently known as the Wild Blueberry Heritage Center.