From 62 semi-structured interviews carried out with young people ages 14-25 who are engaged in the defense of the environment, we explored in this article how the circulation of scientific knowledge on the social media plays a role in engaging young people in defense of the environment to identify how internet can help to support them. As a result, despite respect for science and scientists, young people's processing of scientific knowledge does not always seem to respect the standards of objectification advocated by the scientific approach. This can be problematic because they can appear to be contradictory for their detractors. Helping them to be more efficient in their active role for promoting environmental issues means to support them for a more scientific and reflexive use of social media. Thus, the many debates around environmental education can be enriched by an increasingly precise analysis of the expression of the commitment of young ecologists on the Internet.