He graduated from the École Polytechnique, and holds a background in environmental engineering, and a PhD in environment management, with a particular focus on foresights and futures studies for environmental policies. He has been in charge of developing foresights at the French ministry for Environment, and acted as a researcher in management sciences at AgroParisTech (Paris Institute of Technology for Life, Food and Environmental Sciences) and at CIRED (International Research Centre on Environment and Development).

His research focuses on three fields of environmental policies. First, he  is involved in designing foresights and forward-looking processes for long-term water resources management at the river basin scale in Europe, the Mediterranean Basin, and Western Africa. Second, he developed research projects to analyse the use of foresights at various steps and for various levels of the protection of ecosystems in France and in Morocco. Third, he analyses the role played by scenarios as central elements of expertise for global environmental governance. He has recently been involved in the "Agrimonde" project, producing scenarios about how to feed the world in 2050 in a sustainable way.

Sébastien Treyer is Chair of the scientific and technical committee of the French Facility for the Global Environment (Fonds français pour l’environnement mondial [FFEM]). He is also member of the scientific council of the Seine-Normandie Basin and of the Agence nationale de la recherche's sectoral scientific council "Ecosystems and sustainable development".