The environmental crisis is the most prominent challenge humanity has ever had to battle with, and humanity is currently failing. The Anthropocene—or so called ‘age of humans’—is indeed a period when the survival of humanity has never been so much at risk. This book locates itself in the field of critical green political theory. Fremaux's analysis of the current environmental crisis calls for us to embrace radical shifts in our modes of being; or, in other words, socially progressive innovations that will be described within the unique framework of "Green Republicanism." In offering a constructive and emancipatory delineation of what could be considered an ecological civilization that is respectful of its natural environment and social differences, this book describes how to shift from an ‘arrogant speciesism’ and materialistic lifestyle to a post-anthropocentric ecological humanism focusing on the ‘good life’ within ecological limits. This new political regime calls for a radical reinvention of our societies, a decentering of the humans within our metaphysical worldview, and a withdrawal of the capitalist technosphere at the benefit of the biosphere. It will require a new economic paradigm that replaces the unsustainable capitalist logic of growth by sustainable degrowth and steady economics. Rooted in ethical thinking and political philosophy, this book seeks to offer a concrete roadmap of how sustainable societies can be fostered.