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LONDON (Reuters) - Chopping down fewer trees and caring for the soil may be cheaper and more effective in fighting climate change than curbing emissions from coal plants, the United Nations Environment Programme (UNEP) said on Friday.
Many energy companies and analysts say the world should invest in technology which traps carbon emissions from the flue gas of coal plants and then buries it underground.
But the technology is untested. And according to a UNEP report, there are better natural ways to store carbon.
Trees store the greenhouse gas carbon dioxide (CO2) as they grow, while soil traps carbon in the organic matter of roots and tiny organisms underground.
"Tens of billions of dollars are being earmarked for carbon capture and storage at power stations, with the CO2 to be buried underground or under the sea," said Achim Steiner, UNEP Executive Director, in the report "The Natural Fix? The Role of Ecosystems in Climate Mitigation."
"The Earth's living systems might be capable of sequestering more than 50 gigatonnes (billion tonnes) of carbon over the coming decades with the right market signals," he added.
The world pumped into the atmosphere 8.5 billion tonnes of carbon from burning fossil fuels in 2007.
Global greenhouse gas emissions are increasing at about 3 percent a year and must start falling within a decade to avoid the worst effects of climate change, scientists say. Recession will only slow annual increases temporarily, say analysts.
Soils store more carbon when animal grazing rates are cut and crops grown less intensively -- measures which cost about $5-10 per tonne of avoided CO2 emissions, the report found.
That compares with the cost of trapping greenhouse gases from coal plants of $20-270 per tonne of CO2.
Carbon capture and storage (CCS) works by trapping CO2 from the exhaust gases of fossil fuel power plants and then piping it to underground storage sites, such as disused oil wells. The European Union says it wants 10 to 12 commercial-scale CCS plants by 2015. Analysts say the extra cost is about $1 billion per power plant. Countries joining the technology race include the United States, China, Canada and Australia.
The cost of storing carbon in forests and farms increases the more that is needed, however, because that means competing with profitable alternatives such as intensive food production.
That can cause also cause social problems, for example where planting trees comes at the expense of land used for traditional grazing -- "Sometimes ... the land may be of great importance for local people as rangeland or pasture for livestock, or as a source of wild food or other resources," the report said.
Reporting by Gerard Wynn; editing by Andrew Roche