Secretary-General Ban Ki-moon called?Saturday on young people to help combat the multiple threats faced by the planet such as climate change and environmental destruction, to ensure a sustainable future for generations to come.

Secretary-General Ban Ki-moon

"We have only this Earth, and it is up to us to preserve it," Mr. Ban told young people at the closing ceremony of the youth event at the Alliance of Civilizations Forum in Doha, Qatar.

"Our future is at risk, yours and mine, but also more broadly the future of humankind. You know the threats as well as I: climate change, environmental destruction, growing scarcities of essential resources -- water, food, energy, the clean air we breathe," he said.

Mr. Ban stressed the global nature of these problems, and their need for global solutions. "You understand that, with just one Earth, we cannot afford to fight over religion, race, or any of the other categories that separate us," he said.

"We are, indeed, all under the same roof. We live at a unique moment in human history. We recognize the fragility of our beautiful planet. We recognize our vulnerability to changes in the air and resources around us," he added.

Mr. Ban underscored the importance of nations working multilaterally to tackle global issues and said events like the UN Sustainable Development Conference (Rio+20) in Brazil next year are crucial instruments for international cooperation and progress.

"In Rio, we hope to chart a new path for development -- sustainable development, which means growth consistent with the limitations and opportunities of our natural world."

Mr. Ban made invited young people to join the UN and its campaigns for peace, human rights and environmental sustainability.

"Let us, together, create a movement -- a movement for change, a movement of all nations and all people, united, to advance the great causes of our day," he said.

The fourth annual forum of the United Nations Alliance of Civilizations will start tomorrow and will count with more than 2,000 participants, including political and corporate leaders, civil society activists and faith communities who will meet to discuss joint actions to improve relations across cultures, combat prejudice and build lasting peace.