Montreal Protocol is concerned with:

Question

Accepted Answer

The correct option is 4: Substances that deplete ozone layer

The Montreal Protocol, formally titled the Montreal Protocol on Substances that Deplete the Ozone Layer, is fundamentally an international treaty designed to protect the Earth's stratospheric ozone layer. Finalized in 1987, this landmark agreement was driven by scientific evidence showing that human-made chemicals, particularly chlorofluorocarbons (CFCs) and halons, were severely damaging the ozone shield. The Protocol mandates a step-wise phase-out of the production and consumption of these ozone-depleting substances (ODS) globally. The success of the treaty lies in its specific, actionable focus: controlling and eliminating the precise chemicals that cause ozone depletion, making it one of the most successful environmental agreements in history and the first treaty in UN history to achieve universal ratification.

The incorrect option is 1: Mitigation of climate change

While the Montreal Protocol has had immense positive *co-benefits* for climate change mitigation, its primary concern and legal mandate is not the general reduction of all greenhouse gases. The main international agreement for mitigating climate change, which focuses predominantly on carbon dioxide ($\text{CO}\_2$) and other major warming gases, is the Paris Agreement (and historically the Kyoto Protocol). The climate benefit of the Montreal Protocol arose because the ODS it phased out (like CFCs and HCFCs) also happen to be potent greenhouse gases. This happy coincidence means the Protocol has avoided billions of tonnes of $\text{CO}\_2$-equivalent emissions, but its direct, founding purpose was ozone layer protection.

The incorrect option is 2: Sustainable development

Sustainable development is a broad, overarching concept defined as meeting the needs of the present without compromising the ability of future generations to meet their own needs. While the successful protection of the ozone layer absolutely contributes to the goal of sustainable development by safeguarding human health and ecosystems, it is not the sole or primary focus of the Montreal Protocol. The concept of sustainable development is addressed more comprehensively by major international bodies like the United Nations through the Sustainable Development Goals (SDGs). The Montreal Protocol is a specific solution to a specific environmental crisis, whereas sustainable development is a universal policy framework spanning economic, social, and environmental goals.

The incorrect option is 3: Biodiversity conservation

Biodiversity conservation is primarily governed by the Convention on Biological Diversity (CBD), which focuses on the preservation of species, ecosystems, and genetic resources. While the phase-out of ODS has an indirect, positive impact on biodiversity—by allowing the ozone layer to recover, thereby reducing the harmful ultraviolet (UV) radiation that reaches the Earth's surface and damages plant and animal life—it is not the central theme of the Montreal Protocol. The treaty does not establish protected areas, regulate wildlife trade, or set targets for species preservation, which are the typical concerns of biodiversity conservation agreements. Its focus is on the chemical substances responsible for stratospheric ozone destruction.