How many trees would it take to absorn a tonne of CO2

Carbon offset company co2balance.com say that a tree's ability to absorb carbon dioxide depends on the species, atmospheric temperature, levels of light, water, nutrients, and atmospheric CO2 - and how the woodland is managed. Based on their research they reckon that each sapling they plant will absorb 0.9 tonnes of carbon dioxide per year.

Forests and the European Union Resource Network (FERN) reckon that if this is so, absorbing the UK’s annual greenhouse gas emissions would require planting an area of forest the size of Devon and Cornwall every single year – and maintaining them forever - but they think the concept of accurately predicting trees’ carbon performance is "fantasy" with no solid basis in science.

Not everyone is even convinced that tree-planting works. Critics point out that trees eventually die and rot, releasing carbon back to the atmosphere, and may have serious adverse environmental consequences by soaking up scarce water or decreasing biodiversity.