The project Sensing for Justice - researching the potential of citizen science in environmental litigation and mediation - convened a dialogue roundtable at the Engaging Citizen Science Conference 2022. During the roundtable, participants were invited to reflect along three main lines: (I) how to provide social and legal support to less structured and more spontaneous citizen science initiatives, here framed as ‘reactive’; (II) what type of legal/institutional recognition is desirable for these more ‘reactive’ forms of citizen science; (III) which novel communication approaches - for example, visuals and story-telling - can enable us to enter in dialogue with these initiatives. After these prompts, we asked the participants to react with spoken interventions and drawings. Together, we could draft a ‘manifesto’ voicing the need of reactive environmental citizen science and sketching avenues to ensure that the practice can flourish and have impact.