Timber, carbon and wind risk: towards an integrated model of optimal rotation length

Modern forest management practice increasingly adopts an ecosystem services approach to account for the multiple benefits and objectives of forestry. It is also increasingly linked to climate change adaptation and mitigation strategies. In view of the priority given to these policy agendas, it is important that new models take an integrated approach to accounting for these issues.
This Research Report focuses on the development of a prototype integrated optimal rotation length model. The model is integrated in the sense that it accounts for timber production, climate change mitigation in terms of carbon sequestration and substitution benefits, and climate change adaptation in relation to windthrow risks. Extending traditional models (which focus upon timber production only), to cover the wider benefits of woodlands in the presence of climate change risks, will contribute to more comprehensive comparisons between management alternatives in terms of net present values, rotation lengths and production volumes.
The research illustrates how several models developed by Forest Research (ForestGALES – wind risk evaluation tool, and CSORT – carbon accounting in forestry) can be linked together to produce answers to complex queries. In this case: what is the economically optimal harvesting time when timber and carbon benefits are included in the presence of wind risk?
Currently the model has been tested using Sitka spruce yield class 14. A key result of this test shows that in some cases, optimality involves leaving stands unfelled for the carbon sequestration benefits, while at some windier sites windthrow risk can be the main factor determining optimum rotation length.