Facing global climate crisis, Karl Marx's ecological critique of capitalism more clearly demonstrates its importance than ever. This book explains why Marx's ecology had to be marginalized and even suppressed by Marxists after his death throughout the twentieth century. Marx's ecological critique of capitalism, however, revives in the Anthropocene against dominant productivism and monism. Investigating new materials published in the complete works of Marx and Engels (Marx-Engels-Gesamtausgabe), Saito offers a wholly novel idea of Marx's alternative to capitalism that should be adequately characterized as degrowth communism. This provocative interpretation of the late Marx sheds new lights on the recent debates on the relationship between society and nature and invites readers to envision a post-capitalist society without repeating the failure of the actually existing socialism of the twentieth century.