Spain, whose economy in 1990 lagged other European Union countries, is allowed an increase of 15 percent in its carbon dioxide emissions but the government estimates that it will be facing one of 37 percent in the 2008-12 period.

It aims to offset 20 percentage points of that via United Nations-approved clean energy projects in developing countries, and a further 2 points by planting trees.

Some of the country's regional and local governments are leading the way.

Castilla-La Mancha, an extensive, rural region on Spain's central plain, has already increased its forested area by 1 million hectares (2.5 million acres) to 5 million hectares, its Environment Councillor Jose Luis Martinez told a conference.

It now plans to plant 20 million trees in the next four years, he said.

Madrid, despite its snarling traffic, already claims to be one of the cities with most parks and gardens in the world.

It promises more green spaces and plans to create hanging, vertical gardens to cover buildings.

"We will also plant 1.5 million trees, which will absorb 9,000 tonnes of greenhouse gases a year," Ana Botella, the head of the city hall's environmental department, said.

Officials said this project would be accomplised within the term of the four-year legislature just starting.

The Basque Country is funding the planting of 250,000 trees in Kenya between 2006 and 2009, the regional government's environment councillor Esther Larranaga said.