Future challenges for woody biomass projections

Many drivers affect woody biomass projections including forest available for wood supply, market behavior, forest ownership, distributions by age and yield classes, forest typologies resulting from different edaphic, climatic conditions, and last but not least, how these factors are incorporated into projection systems. Net annual increment has been considered a useful variable for estimating future wood and biomass supply, but it can be misleading. In Europe, two different approaches have been used: a common European-level tool for all countries (“top-down” approach); and national tools (“bottom-up” approach). The trade-offs are that the “top-down” approach produces comparable results among countries, but ignores most of the topographic, climatic, vegetative and socio-economic conditions that are unique to countries and regions. The “bottom-up” approach better accommodates national and regional conditions but at the cost of comparability among country level results. A brief discussion of how these issues are handled in North America provides insights into different approaches and their linkages to national circumstances regarding country sizes, ownerships and general political frameworks. Another challenge lies in accommodating climate change and uncertainty in projections. Finally, working closely with experts from the demand side to minimize possible misunderstandings is also required. The first step towards increasing comparability of results from country-level projection systems is to understand the differences among these tools. Only then, can progress be made in terms of harmonizing the input and output variables or even progressing towards a common methodological approach and software structure