"I hope this doesn't just become another academic Earth Day and that there is a real implementation plan," said San Francisco Supervisor Ross Mirkarimi, co-founder of the state Green Party. "San Francisco is very good at investigating our options that steer us away from fossil fuels. But we have a long ways to go, especially in comparison to many other cities that will be visiting."
Others are cautiously complimentary. When Newsom ran for mayor, environmental organizations gave him a D compared with opponent Matt Gonzalez's A, based on their environmental voting records on the Board of Supervisors.
But as mayor, they say, Newsom has shown a greater interest in environmental causes, such as renewable energy.
John Rizzo, chairman of the San Francisco Bay chapter of the Sierra Club, a sponsor of some World Environment Day events, said he doubts the protocols that will be adopted will become solutions. But "to have the general public know these are problems -- that's worthwhile.... I think it's going to be hyped. But there is something there," he said. "It's not exactly fluff."
Richard Register attended the U.N. event in 1972 in Stockholm when World Environment Day was created. His Berkeley-based Ecocity Builders is dedicated to ecologically healthy cities that are not reliant on automobiles, and he has traveled the world to find them. San Francisco never made the list.
Others say that, by playing host to the conference, San Francisco has truly found a way to, as the slogan goes, think globally and act locally.
Many of the world's strongest national political figures are emerging from the halls of city government, DeLeon said, and they have the power to act.
"A lot of people like myself on the left, we've given up on national-central governments," DeLeon said. If the environmental movement is going to advance, "it's going to happen in the cities and percolate up."
Oakland's Ella Baker Center for Human Rights recruited nearly two dozen grass-roots minority groups to discuss social justice at the event. They will call on global mayors to address urban poverty by training residents in green technologies.
"Mayors are in a better position than presidents, frankly, to give a green light to the green economy," said executive director Van Jones.
"It's at the local level that the zoning decisions are made, that tax credits are given, that community development plans are approved."