Biosphere Constitutionalism: An Institutional Design Framework for Earth System Governance

Earth System Governance scholarship has documented the mismatch between planetary-scale ecological disruption and fragmented institutions of environmental decision-making. This article develops biosphere constitutionalism as an institutional design framework for addressing that mismatch. It argues that biospheric integrity should not be treated merely as an interest within constitutional balancing, but as the biophysical condition under which interests, balancing and constitutional reasoning remain possible. From this position, the article derives three institutional functions — standing, priority and representation — corresponding to integration, thresholding and absence of self-representation. The framework is differentiated from environmental constitutionalism, Earth governance through trusteeship and ecological democracy, and positioned within Earth System Law as one institutional element rather than a competing paradigm. Five design pathways operationalise the functions, including a worked application to European Union climate governance. The article specifies constitutional architecture without proposing world government. Preprint, not peer-reviewed. Manuscript completed in May 2026. Its argument was subsequently developed into the Declaration for an Earth Constitution, version 1.6.