A grassroots campaign to plant trees around the globe has announced that it is raising its target from 1 billion trees to 7 billion trees, the United Nations announced today.

The campaign, which is under the patronage of Nobel Peace Prize Laureate and Kenyan Green Belt Movement founder Professor Wangari Maathai and Prince Albert II of Monaco, also announced today that in 18 months it has seen two billion trees planted, double its original target.

The campaign was launched by the UN Environment Programme (UNEP) and the World Agroforestry Centre (ICRAF) in 2006 as a response to the threat of global warming.

UNEP Executive Director Achim Steiner said today: “Having exceeded every target that has been set for the campaign, we are now calling on individuals, communities, business and industry, civil society organizations and governments to evolve this initiative on to a new and even higher level by the crucial climate change conference in Copenhagen in late 2009.”

Tree planting remains one of the most cost-effective ways to address climate change. Trees and forests play a vital role in regulating the climate since they absorb carbon dioxide. Deforestation, in turn, accounts for over 20% of the carbon dioxide humans generate, rivaling the emissions from other sources.

Trees also play a crucial role in providing a range of products and services to rural and urban populations, including food, timber, fibre, medicines and energy as well as soil fertility, water and biodiversity conservation.

In terms of geographic distribution, Africa is the leading region with over half of all tree plantings. 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).

The two billionth tree was put into the ground as part of an agroforestry project carried out by the UN World Food Programme (WFP). It has now planted 60 million trees in 35 countries to improve food security.