Wallace graduated from Yale University with a Bachelor of Arts degree in philosophy in 1977 and from the Missouri School of Journalism at the University of Missouri in Columbia, Missouri with a Masters in Print and Broadcast Reporting.
Wallace began his career as a reporter for CBS News Radio, the Atlanta-Journal Constitution in El Salvador in 1983. He moved his base of operations from El Salvador to Nicaragua in 1985 in order to cover the escalating Contra War and the Reagan Administration’s efforts to oust the leftist Sandinista government. He continued writing for Cox Newspapers until early 1986, by which time he was writing for Newsweek and The Independent (UK). He moved to Guatemala in early 1989 and became Central America Correspondent for The Guardian.
Since the early 1990s, Wallace has worked as a magazine writer and photographer, while producing long-form network news magazine programs on war, international organized crime, indigenous affairs, and the environment. The bulk of Wallace’s work has been for the various entities of National Geographic, including National Geographic magazine, National Geographic Adventure, National Geographic Traveler, and the National Geographic Channel. His assignments for National Geographic have taken him from the rainforests of Brazil to the high mountain peaks of the Peruvian Andes and the rugged, windswept Wakhan Corridor in the western Himalayas of Afghanistan. Wallace specializes in the coverage of conflict over land and resources in remote locations, where crucial historical processes are unfolding beyond the sight of the rest of the world.
Wallace was contracted by the World Bank to document Bank-financed projects around the world in 2004. His travels took him to Morocco, Senegal, Mauritania, Tanzania, Eritrea, Yemen, Bulgaria, Turkey, India, Bangladesh, Thailand, Peru, Brazil, and Colombia. Following his work with the World Bank, Wallace worked on assignment for National Geographic and accompanied conservationist George Schaller on an expedition into the remote Wakhan Corridor of Afghanistan's Badakshan Province. Over the course of two months, Wallace and Schaller travelled by foot, horseback and yak; the journey was featured in the December 2006/January 2007 edition of National Geographic Adventure.
Wallace’s writing has appeared in National Geographic, National Geographic Adventure, National Geographic Traveler, Harper's, Sports Afield, Conde Nast Traveler, Newsweek, Interview, The Nation, and the Village Voice among many other publications.