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.
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.
His travels took him to Morocco, Senegal, Mauritania, Tanzania, Eritrea, Yemen, Bulgaria, Turkey, India, Bangladesh, Thailand, Peru, Brazil, and Colombia.
Photography credits include: National Geographic, Outside, Details, Interview, Newsweek, The Washington Post, Smithsonian magazine, The Economist, and The New York Times.