The main aim of the Basel Convention is to focus on the conservation of biodiversity. This international treaty, which came into effect in 1992, aims to reduce the movement of hazardous waste between countries. It aims to control and limit the generation, transportation, and disposal of hazardous waste, especially in developing countries. The convention recognizes that hazardous waste can have significant impacts on the environment and human health if not handled properly. By regulating the movement of hazardous waste, the convention aims to minimize the risks associated with its improper disposal and protect the diversity of ecosystems. This helps to maintain a balance between human activities and the preservation of natural resources. Therefore, option 2, biodiversity conservation, is the correct answer.