De Baar has supported the farming of algae for biofuel and has warned about the speed at which ocean acidification intensifies. De Baar is globally well recognised for his expertise. In 2009, Nature quoted him as follows: "Ocean iron fertilization is simply no longer to be taken as a viable option for mitigation of the CO2 problem." The high-ranking scientific journal Marine Chemistry dedicated an issue to him and described him as "a chemical oceanographer who investigated the oceans with the conviction that only true integration of biology, chemistry, and physics is pivotal to understand the inner workings of the oceans. He was one of the initiators of the Joint Global Ocean Flux Study (JGOFS) and of GEOTRACES."