Forests cover one third of the Earth's land area, containing up to 80 per cent of its above ground terrestrial carbon and 40 per cent of its underground carbon. They therefore represent a critical part of the global carbon budget. Growing trees to sequester carbon can be a low-cost way of reducing net emissions for many countries.
Forest ecosystems are also a major contributor to the world's freshwater resources, by retaining sediment, reducing soil erosion, encouraging water filtration in soil, helping to replenish groundwater sources and storing water in the soil. However, the many attributes of forests can create conflicting objectives for forest management. For example, if the aim is to maximise timber production, what are the effects on carbon sequestration or water supplies?
A forest near the city of Artvin in northeast Turkey formed the basis of a case study. The researchers placed economic values on its three main resources - timber, water and carbon sequestration. The financial value of carbon stored was based on the cost of avoiding carbon emissions. Water and carbon's value is not presently considered in forest management.
The researchers found that different strategies lead to very different outcomes, with key trade-offs between each of the objectives. Timber production decreased by up to 6.6 per cent when a carbon target is incorporated into forest management strategy. Conversely, carbon sequestration diminishes by up to 58 per cent when timber targets are maximised, and by 20 per cent for water targets.
Measuring carbon in forests is a key way of fulfilling requirements under the UN Framework Convention on Climate Change and the Kyoto Protocol. The authors write that by quantifying the interactions of different values of forests, it is easier to understand forest dynamics and move towards sustainable forest management. As such, alternative forest management planning strategies can be developed which best meet the needs of public demand or environmental legislation.
There are a considerable number of other values in forests, including recreation, soil protection and biodiversity. The authors write that good management practices should ensure that non-wood products and services from forests are explicitly included in order to achieve the best balance of outputs. The economic role played by recycling timber products should also be taken into account, as should land-use aspects of forest management such as links between green areas, the size of harvest blocks, the effect of clearcutting on neighbouring areas and wildlife habitat.