South African officials announced yesterday that the next Earth Summit, to be held in Johannesburg in 2002, will focus on worldwide access to drinking water and safeguarding children. The summit — officially called the U.N. World Summit on Sustainable Development — has the modest agenda of reviewing progress since the 1992 Rio summit, looking at the impact of globalization on development, energy use, and land degradation, and addressing the imbalance between wealthy industrialized nations in the Northern Hemisphere and poorer developing nations in the Southern Hemisphere.