UN Secretary General Ban Ki-moon has called for a single global vision from world leaders to address the problems of world hunger and pollution. Mr Ban's comments came at the start of a UN conference in Rome aimed at stabilising world food prices. He said the summit needed to co-ordinate closely with the UN climate meeting at Copenhagen next month. The UN says one billion people are hungry and that food production must increase to feed a growing population.<br/>The World Summit on Food Security comes a year after major rises in food prices caused chaos across the globe.