The announcement of the birth of the world's six billionth citizen is just a ploy to call attention to the effects of population growth. Across the world, babies arrive by the hundred every minute of the day - most in poorer countries where infant mortality rates are high and life expectancy is low. The world that baby Mevic will grow up in faces profound challenges. He is already among the privileged minority by being born into a part of the developed world where, in spite of recent conflict, he can probably count on food and shelter, decent health care and education. For millions of children born into parts of Africa, Latin America and Asia, subsistence-level existence is as much as they dare hope for. Despite the many technological advances, the gap between rich and poor is widening. But at least there are some signs that young Mevic will grow to manhood in a world where real effort is made to see the benefits are more equally shared. The proposal to cut Third World debt is one move, pressure on drug companies to cut costs to poorer nations and pour more resources into researching tropical diseases is another. And there are some signs that in the next 100 years the pendulum may swing against the nations that are prosperous. Governments in Japan and Germany, for example, worry that a falling birthrate and increasing longevity will result in a serious population imbalance. The problem of how to deal with the economic and social consequences of a minority of taxpayers supporting an ageing population is one that occupies many Western planners. Another problem, which takes no account of wealth or position, is the depredations the Earth is subjected to as more people compete for less space. Disappearing rain-forests affect climate and contribute to the natural disasters that occur with such frightening regularity. The fragile ecological balance is disturbed by the slaughter of endangered animals, overfishing, and uncontrolled development. Doomsayers predict the worst consequence of overpopulation will be competition for water. In the Middle East, Turkey, and the Indian subcontinent water supply is already causing conflict. Countries that control the headwaters of mighty rivers can hold neighbours to ransom by diverting the flow. According to the World Bank, 'the wars of the next century will be fought over water'. It is problems of that kind that Mevic's generation will have to try to solve.