Nepal, Sept. 1 -- Small island nations such as Tuvalu, Kiribati, the Maldives and Marshall Islands are particularly vulnerable to climate change. Rising seas, stronger storms, freshwater shortages and damaged infrastructure all threaten their ability to support life.

Some islands even face the grim possibility of being abandoned or sinking beneath the ocean. This raises an unprecedented legal question: Can these small island nations still be considered states if their land disappears?

The future status of these nations as "states" matters immensely. Should the worst happen, their populations will lose their homes and sources of income. They will also lose their way of life, identity, culture, heritage and communities.

At the same time,...