About: Common but differentiated responsibilities (CBDR), principle of international environmental law establishing that all states are responsible for addressing global environmental destruction yet not equally responsible. The principle balances, on the one hand, the need for all states to take responsibility for global environmental problems and, on the other hand, the need to recognize the wide differences in levels of economic development between states. T
hese differences in turn are linked to the states’ contributions to, as well as their abilities to address, these problems. CBDR was formalized in international law at the 1992 United Nations Conference on Environment and Development (UNCED) in Rio de Janeiro.