The United Nations is looking for innovative ways to combat global warming. One initiative aims to plant seven billion trees worldwide - nearly one for every person on the planet. From U.N. Headquarters in New York, VOA's Alex Villarreal has more.

Head of the U.N. Environment Program, Achim Steiner, says the public response to the Billion Tree Campaign has been overwhelming.

The initiative's call to action prompted the planting of two billion trees in just 18 months. Its success has inspired an even more ambitious goal. UNEP says it wants seven billion trees planted by the U.N. Climate Change Conference in 2009.

"Essentially, we are saying for every citizen on this planet, let us take this number as a target," Steiner said. "It is an ambitious target, but it is also a very practical expression of this idea that people can do something about climate change, and they can also send a very powerful message."

Trees play a critical role in regulating the climate, since they absorb carbon dioxide from the air. When they are destroyed, carbon is released. Deforestation accounts for more global emissions each year than any other source - cars, trucks and planes included.

Trees also contribute to soil fertility, water and the overall health of the ecosystem. Steiner says this makes them integral to the productivity of agricultural land - especially important now, amid the global food crisis.

UNEP and the World Agroforestry Centre launched the Billion Tree Campaign at the 2006 climate change conference, as a way to empower citizens to fight global warming at the grassroots level.

Nobel Peace Prize Laureate, Wangari Maathai, inspired the campaign with a tree-planting movement in Kenya. She is now a patron of the U.N. initiative along with Prince Albert of Monaco.

Since the launch, the Billion Tree campaign has sparked plantings in more than 150 countries. More than half the total has been planted on the African continent, with 700 million in Ethiopia alone.

The initiative's support base includes heads of state, multi-national organizations and individuals - who make up half of all participants. People who would like to help can go online and make a pledge.