Wellington teenager Brittany Trilford has given world leaders an ultimatum to "decide the fate of your children", at the Rio+20 summit.
The Queen Margaret College student addressed world leaders from 191 UN members, including 86 presidents and heads of government, at the summit in Rio de Janeiro, Brazil, challenging leaders to lay the foundation for a more sustainable world.
The three-day event comes 20 years after Rio's first Earth Summit when nations vowed to roll back climate change, desertification and species loss.
"I stand here with fire in my heart. I'm confused and angry at the state of the world. We are here to solve the problems that we have caused as a collective, to ensure that we have a future," said Trilford, winner of the "Date with History" youth video speech contest.
Trilford said she was at the summit to "fight for her future".
"I would like to end by asking you to consider why you are here and what you can do here.
I would like you to ask yourselves: Are you here to save face? Or are you here to save us?
"You have 72 hours to decide the fate of your children - my children - my children's children - and I start the clock now."
Trilford asked delegates to think back 20 years ago to the first Rio Earth Summit and the promises made.
"They made great promises, promises that, when I read them, still leave me feeling hopeful. These promises are left not broken, but empty. How can that be?
"When all around us is the knowledge that offers us solutions. Nature as a design tool offers insight into systems that are whole, complete, that give life, create value, allow progress, transformation, change."
The summit was formally opened by UN Secretary General Ban Ki-moon, who warned that "time is not on our side'' for fixing a mounting list of problems.
In his remarks, the Ban praised Brazil, the summit host, for securing a deal on the summit's final draft statement.
"We are now in sight of a historic agreement," the UN chief said.
"The world is watching to see if words will translate into action as we know they must.
"Rio+20 is not an end but a beginning. It's time for all of us to think globally and long term, beginning here now in Rio, for time is not on our side," he said.
Maldives President Mohamed Waheed came to the podium to announce that his Indian Ocean archipelago planned to set up the world's biggest marine reserve to protect its fisheries and biodiversity.
He said the Maldives would become "the single largest marine reserve in the world", where only sustainable and eco-friendly fishing will be allowed.
"It will exclude deep-sea, purse-seining and other destructive techniques," he added, referring to a fishing technique in which a bag-shaped seine net is used to ensnare fish and other catch.
Waheed did not spell out how big the reserve would be, but said, "We can do it in a short time. I hope we can do it in five years."
A total of 191 speakers were to take the floor until Friday when the summit leaders are to give their seal of approval to a 53-page draft document agreed on by their negotiators Tuesday.
The draft outlines measures for tackling the planet's many environmental ills and lifting billions out of poverty through policies that nurture rather than squander natural resources.
Earlier, the summit was launched to a three-minute movie, "State of the Planet: Welcome to the Anthropocene'' that gave a visual trip through the dramatic changes in the environment since the Industrial Revolution.
The Anthropocene is the name given by many scientists for a new era in Earth's history. It derives from Greek words to indicate the era of humans.
Brazilian President Dilma Rousseff, who was elected president of the conference, said she had no doubt "that we will be up to the challenges that the global situation imposes on us".
As the summit got under way, eight multilateral development banks announced that they would set aside US$175 billion to finance sustainable transport systems over the next decade.
The pledge was made jointly by the World Bank, Asian Development Bank, African Development Bank, Inter-American Development Bank, CAF-Development Bank of Latin America, European Bank for Reconstruction and Development, European Investment Bank and Islamic Development Bank.
Some of the most contentious issues discussed at the conference were proposed measures to promote a green economy and the "Sustainable Development Goals'' that are set to replace the United Nations' Millennium Development Goals after they expire in 2015.
Connie Hedegaard, the European Union commissioner for climate change, said Europe had pushed for a more ambitious text.
"I think that many Europeans, including the ministers, the presidency, the commission, fought for more ambition, fought for more commitments, more deadlines,'' she told AFP.
"We do not get everything we want, but we secure progress.
Environmentalist groups meanwhile were scathing in their criticism of the draft.
"There's absolutely nothing there for people and the planet,'' Daniel Mittler, political director of Greenpeace International, told AFP.
- Herald Online and AFP