Räthzel discusses the transformative work of union environmentalists in one of the largest Spanish trade union confederations. She explores how 'organic intellectuals' coming from the resistance movement against the Franco regime were capable to take advantage of a favourable conjuncture of societal and organisational conditions. Connecting Marxism with environmentalism, they created an extensive set of environmental policies and structures, including hundreds of environmental representatives throughout the country, a research institute and an international organisation reaching out to unions in the Global South. Based on documents and the life-histories of the protagonists, it is argued that the success, crisis and revival of this 'environmental project' can only be understood by analysing the relationship between structural affordances and the role of individuals as promoters of change.