For 12 days in June 1992, more than 35,000 environmental activists, politicians, and business representatives, along with 9,000 journalists, 25,000 troops, and uncounted vendors, taxi drivers, and assorted others converged on Rio de Janeiro, Brazil for the United Nations Conference on Environment and Development. Known as the Earth Summit, this was the largest environmental conference in history; in fact, it was probably the largest non-religious meeting ever held. Like a three-ring environmental circus, this conference brought together everyone from pin-striped diplomats to activists in bluejeans and indigenous Amazonian people in full ceremonial regalia. One cannot say yet whether the conventions and treaties discussed at this summit meeting will be effective, but they have the potential to make this the most important environmental meeting ever held.

The first United Nations Conference on the Human Environment met in Stockholm in 1972, exactly 20 years before the Rio de Janeiro meeting. Called...