Assessing the sustainability of timber harvests from natural forests: Limitations of indices based on successive harvests

The concepts of sustainable original harvest (SOH) and sustainable disturbance harvest (SDH), and simple indices such as the ratio of successive harvests do not provide a reliable indication of the sustainability of a harvest. Some limitations of these concepts are illustrated in the context of selection harvesting of timber from natural forests. Four models are used to demonstrate that maintaining an SOH or SDH indicates little about the long-term sustainability of a timber harvest. The concepts may offer greater utility in evenaged systems harvested by clear-felling, but still suffer the limitation that many factors may mask any change in site productivity. Any measure of sustainability should include an appraisal of the condition and vitality of the residual resource. Simple indices based on successive harvests do not consider the residual stand, and can be misleading.