Prior to his appointment as Managing Director of the Alliance of Bioversity international and CIAT in Asia, Stephan was Bioversity International's Deputy Director General for Research for almost a decade. Before joining Bioversity International, Stephan worked for 16 years with the International Institute of Tropical Agriculture (IITA) on a variety of programmes related to tree crops, the environment, and farm diversification in the forest margins of West and Central Africa. From 2002 until he left IITA, he was the Regional Programme Manager of the Sustainable Tree Crops Programme - a public-private partnership and innovation platform that was seeking to increase the income of West and Central African cocoa farmers in an environmentally and socially responsible manner.
He was also the coordinator of the working group on agronomic/landscape sustainability in a related programme called the ASB Partnership for the Tropical Forest Margins hosted by the World Agroforestry Centre.
In addition, he spent 4 years on integrated weed management and farming systems research at the University of Guelph, Canada, after completing his PhD.