Growing stock is defined as the standing volume of the trees in a forest above a certain minimum size. Higher growing stock signifies more standing biomass, which often translates to better forest conditions. But it is important to note that standing tree volume alone is not a sufficient metric for detailed analysis of forest health. For example, future wood supply is highly dependent on the diversity and distribution of tree species and ages within tree stands. These are also critical parameters for maintaining biodiversity. If carbon sequestration is the major question of interest, we must also look at the amount of carbon sequestered in the soil, which may not be directly correlated to a forest’s tree volume. Another specific objection to using growing stock can be that converting primary forests to forest plantations may increase tree volume, but degrade overall ecological conditions. It is also uncertain whether plantations actually match natural forests with equal tree volume. Furthermore, the value of plantations varies significantly depending on how wood is valued relative to biodiversity in the local context. For the purposes of target selection in this metric, we have decided to assume that an increase in growing stock indicates improving forest conditions while a decrease in growing stock indicates degrading forest conditions. The 2008 EPI target is zero change in growing stock as calculated by FAO in the years 2000-2005.
