The main aim of the Kyoto Protocol was to address the issue of global warming. It was an international agreement developed in 1997 under the United Nations Framework Convention on Climate Change (UNFCCC). The protocol set binding obligations for developed countries to reduce their greenhouse gas emissions. The goal was to limit the increase in global average temperature to below 2 degrees Celsius above pre-industrial levels. While the conservation of wetlands and biodiversity are important environmental concerns, the main focus of the Kyoto Protocol was specifically on the reduction of greenhouse gas emissions and mitigating the impacts of global warming. Therefore, option 3 - Global Warming, is the correct answer.