By Alister Doyle, Environment Correspondent

OSLO, May 13 (Reuters) - A campaign to plant trees worldwide set a goal on Tuesday of seven billion by late 2009, just over one for each person on the planet, to help protect the environment and slow climate change.

The U.N. Environment Programme (UNEP), an organiser of the tree planting drive begun in late 2006 with an initial goal of a billion by the end of 2007, said governments, companies and individuals had already pushed the total above 2 billion.

It set a target on Tuesday of an extra five billion plantings by the time a U.N. climate conference in Denmark starts on Nov. 30 next year that is meant to agree a new long-term treaty to combat climate change beyond the U.N.'s Kyoto Protocol.

"In 2006 we wondered if a billion tree target was too ambitious; it was not," said Achim Steiner, head of UNEP.

"The goal of two billion trees has also proven to be an underestimate. The goal of planting seven billion trees, equivalent to just over a tree per person alive on the planet, must therefore also be do-able," he said in a statement.

UNEP said that safeguarding and planting forests were among the most cost-effective ways to slow climate change, blamed by the U.N. Climate Panel on emissions of carbon dioxide from burning fossil fuels in factories, power plants and cars.

Trees soak up carbon dioxide as they grow and release it when burnt or when they rot. Deforestation accounts for over 20 percent of the carbon dioxide humans generate.

The campaign registers pledges of plantings on the Internet but does not check that all seedlings or saplings are actually planted or survive.

"Regional and national governments organized the most massive plantings, with Ethiopia leading the count at 700 million, followed by Turkey (400 million), Mexico (250 million), and Kenya (100 million)," it said.

Millions of individuals have also taken part, including schoolchildren or religious groups. "It has given expression to the frustrations but also the hopes of millions of people around the world," Steiner said.

One U.N. official said that seven billion trees would, as they grow, soak up roughly the same amount of carbon dioxide emitted by Russia in a year. Russia is the third largest emitter of greenhouse gases behind the United States and China.

Among projects, mangroves were planted in Indonesia after the devastating 2004 tsunami to help protect coastline. And the Replant New Orleans initiative sponsored plantings of fruit trees to help communities recover after Hurricane Katrina.

-- For Reuters latest environment blogs click on: http://blogs.reuters.com/environment/ (Editing by Matthew Jones)

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