Models of carbon storage in softwood and hardwood trees and forest soils and its emission from timber products and waste are developed and integrated with data on storage benefits to yield estimates of the value of the net carbon flux generated by afforestation. The long-term nature of the processes under consideration and the impact of varying the discount rate are explicitly incorporated within the model. A geographical information system (GIS) is used to apply carbon sequestration models to data on tree growth and soil type distribution for a large study area (the entire country of Wales). The major findings are: (1) all three elements under analysis (carbon sequestration in livewood, release from different products and waste, and storage or emission from soils) play a vital role in determining overall carbon flux; (2) woodland management has a substantial impact upon carbon storage in livewood however the choice of discount rate exerts the largest overall influence upon estimated carbon flux values; (3) timber growth rates (yield class) also have a major impact upon values; (4) tree species does affect storage values, however this is less important than the other factors listed above; (5) non-peat soils generally sequester relatively low levels of carbon. Planting upon peat soils can result in very substantial emissions of carbon which exceed the level of storage in livewood.
The GIS is used to produce valuation maps which can be readily incorporated within cost-benefit analyses regarding optimal locations for conversion of land into forestry.