Leontien has been active in the field of sustainable development for seventeen years. She started at UNEP (Division of Technology, Industry and Economics). From 2004, she has been working for the Global Reporting Initiative in Amsterdam. She has been a former Director at the GRI focusing on small and medium-sized enterprises (SMEs) and setting up the supply chain reporting programme. Her expertise is focused on communicating CSR performance by companies regardless size or sector, applying the GRI Guidelines, and the management process of sustainability reporting. In 2009 she became a LEAD Fellow by completing the LEAD Europe Leadership for Sustainable Development Program.
Leontien is now CEO of SIM Supply Chain Information Management. Her main aim is helping retailers and brands in the FMCG sector understanding their supply chain and using these insights to create change in environmental and social conditions.