The global environment summit that ended Friday drew nearly 100 world leaders and more than 45,000 other people to Rio de Janeiro, cost tens of millions of dollars, and may produce one lasting legacy: convincing people it's not worth holding global summits.

The U.N. Conference on Sustainable Development, a once-a-decade meeting aimed at reconciling economic and environmental aspirations, produced a nonbinding declaration committing the world's politicians to modest goals.

Proposals set out at the beginning, such as providing universal energy access and doubling renewables by 2030, were left on the cutting-room floor.

"I don't know if they'll ever do this again, and I don't know if we'll need it again," said the Pew Environment Group's director of international policy, Susan Lieberman. She said she was at least pleased that oceans received more attention this year. "It's a 12-ring circus here."

The so-called Rio+20 Earth Summit featured plenty of theatrics, including Greenpeace's unfurling Thursday of an "Arctic Scroll," signed by such luminaries as Paul McCartney and Robert Redford, to be planted on the North Pole seabed to draw attention to global warming. The summit also hosted dozens of serious policy discussions.

Conservation International Vice President Carlos Manuel Rodríguez said he was encouraged that Scandinavian leaders pledged support for systems that would place an economic value on clean waterways, intact forests and other important ecosystems.

Ecuador's secretary of state, Ivonne Baki, who is trying to recruit donors to compensate her nation for protecting its Yasuni National Forest rather than extracting the oil beneath it, said she was pleased more than 500 people came to her presentation.

"It gives an example to the world of a developing country doing something to preserve one of the most biodiverse places in the world, the Amazon," she said.

Companies and countries alike used the gathering, with tens of thousands of attendees, as a moment to make new environmental pledges. Grenada announced its transport and electricity sectors will use only clean-energy sources by 2030; Unilever promised to cut its greenhouse-gas emissions in half by 2020.

Nonetheless, veterans of the international process and some of its newest participants wondered if such negotiations can produce meaningful outcomes.

Manish Bapna, acting president of the World Resources Institute, said the combination of "strong-vested interests" and the need for unanimous approval in the United Nations led to a final agreement that reflects the "lowest common denominator."

"I think this process is totally broken," wrote Melinda Kimble, the U.N. Foundation's senior vice president, who as a State Department negotiator helped forge the 1997 Kyoto Protocol on global warming. "While we are searching for a new paradigm to advance international cooperation, this meeting is definitely not a model."

Brittany Trilford, 17, a New Zealander who won a contest to attend and represent global youth in an address to the assembled delegates, said she was shocked by the final product.

"This doesn't look very ambitious, and it doesn't look like it will do anything," she said.

Kimble and other experienced negotiators such as Yvo de Boer, who previously oversaw the U.N. Framework Convention on Climate Change, said the summit was hampered by the economic downturn and lack of a shared vision about how the world should tackle its long-term problems. President Obama skipped the meeting, as did British Prime Minister David Cameron and German Chancellor Angela Merkel.

Secretary of State Hillary Rodham Clinton addressed delegates Friday, in Obama's place. She spoke of forging partnerships that would harness "the power of the market" rather than relying solely on governmental action. "It should be said of Rio that people left here thinking, as the late Steve Jobs put it, not just big, but different."