San Francisco-based "eco restoration" company Planktos-Klimafa will plant the trees over a 7,000-hectare (17,000-acre) area, Jose Sanchez de Toca y Alameda, Pontifical Council of Culture under-secretary, told Vatican Radio.

He said that although the Vatican's emissions were low, it "wanted to do its bit to fight pollution on earth and to contribute to improving the planet that God gave to humans so that they could be the servants of nature and not its masters."