The surface of our planet is mainly water, yet usable water is in short supply. In some parts of Africa people have to walk several kilometres a day to get water, and they are the lucky ones. There, and in Asia, the prospect of conflicts over water is increasing. A particular example is the scheme to bring more water into Turkmenistan and its capital city, Ashgabat.

One of the outstanding phenomena of the 20th century was the huge migrations of population it witnessed. It is natural to think first of the effects of war, exacerbated by nationalism and beliefs about ethnicity. A major example is the forced displacement of millions of people in Europe and the Middle East in 1945 and afterwards. But these movements are dwarfed by the migration of rural dwellers to urban areas, a process with origins in the industrial revolution but which in the past 60 years has turned from a stream to a tsunami. (Commentary)