One such mechanism is the creation of carbon sinks, primarily via sequestration of carbon in planted forests. Trees sequester CO 2 by using the power of the sun to split and rejoin CO 2 and water to release oxygen and form complex molecules such as sugar, starch, cellulose and lignin. These are the building blocks for stems, branches, leaves and roots. About half of a tree's dry weight of biomass is carbon. In order to contribute to a reduction in greenhouse gases under the Kyoto Protocol, new planted forests need to be established on land cleared prior to 1990 and to involve a change in land use from agriculture or grazing to forestry.
Carbon sinks supplement direct emission reduction actions.
Reduction of greenhouse gas emissions via carbon sinks can only ever supplement direct emissions reductions at source. A simple calculation demonstrates why this is so. Between now and the end of the first Kyoto commitment period in 2012, planted forests could sequester on average 20 tonnes CO 2 -e per hectare per annum. This represents less than 2.5 per cent of the 1997 emissions for Australia. Credits are measured by how many tonnes of greenhouse gases are not emitted by an improved practice, or are captured in biomass and thus could be used to offset other emissions.