International law reflects the values shared by States and has helped them face the most consequential challenges of the day. After the Second World War, the most significant challenge was to preserve international peace and security, as well as to guarantee basic human rights. In the twenty-first century, States face a new challenge: climate change and its consequences, and, ultimately, the survival of all mankind. Unfortunately, the consequences of climate change are highly visible – for example, extreme weather conditions (droughts, heatwaves and devastating storms, floods in areas where people have never experienced similar events before), melting ice in the Arctic, the extinction of some native plant and animal species and the appearance of unknown invasive species in the same area.