The correct option is Rio de Janeiro, 1992.
Explanation
The United Nations Conference on Environment and Development (UNCED), commonly known as the Earth Summit, was a landmark international conference aimed at reconciling worldwide economic development with the protection of the environment.
Analysis of Options:
- Stockholm, 1972 is incorrect: The Stockholm Conference (1972) was the United Nations Conference on the Human Environment. While it laid the foundation for global environmental governance, it predates the Convention on Biological Diversity.
- Rio de Janeiro, 1992 is correct: The Earth Summit was held in Rio de Janeiro in 1992. Three major conventions were opened for signature at this summit:
- The Convention on Biological Diversity (CBD).
- The United Nations Framework Convention on Climate Change (UNFCCC).
- The United Nations Convention to Combat Desertification (UNCCD) (conceptually initiated here, adopted later).
- Kyoto, 1997 is incorrect: The conference in Kyoto (1997) led to the adoption of the Kyoto Protocol, which operationalized the UNFCCC by committing industrialized countries to limit and reduce greenhouse gas emissions.
- Johannesburg, 2002 is incorrect: The Johannesburg Summit (2002) was the World Summit on Sustainable Development (Rio+10), held to review the progress of the commitments made at the 1992 Earth Summit.
Key Takeaway: The Convention on Biological Diversity (CBD) was signed at the Earth Summit in Rio de Janeiro in 1992, along with the adoption of Agenda 21 and the Rio Declaration.