At the 1992 UN Conference on Environment and Development — the Earth Summit in Rio de Janeiro — more than 150 states opened two major treaties for signature: the UN Framework Convention on Climate Change (UNFCCC) and the Convention on Biological Diversity (CBD). The UNFCCC established the goal of stabilising greenhouse-gas concentrations and the conference machinery that later produced the Kyoto Protocol and Paris Agreement; the CBD committed signatories to conserve ecosystems and species. The summit also produced Agenda 21, a programme for sustainable development. Together they marked the first comprehensive global framework for environmental governance.
The Rio conventions created the international climate and biodiversity regimes that now shape urban policy, pushing cities towards emissions targets, denser low-carbon development and limits on land consumption at the urban edge.