one that may expand with the development of a market for slash. Given the length of forest rotations under Canadian climatic conditions, whole tree re- moval is still fairly new. We may not have ob- served the full consequences of this practice on forest productivity yet. So, while this may sound overly dramatic, we may have caused unintend- ed negative impacts on the functioning of the ecosystem, impacts that will appear before our eyes only in upcoming decades. Or maybe not. Still, here it is worth recalling that the whole idea of forest biomass for bioenergy being “carbon- neutral”, as opposed to fossil fuels, assumes that the harvested stands will actually grow back and be as well-stocked and productive as they were before harvesting. If there’s a risk that increased biomass removal damages the ecosystem and hinders tree growth and carbon sequestration in future rotations, biomass utilization may not be so ‘neutral’ after all. NOW THE GOOD NEWS In Canada, concerns about the sustainability of intensive biomass removal were first voiced in the 1970s, when the oil crisis pushed prices of fossil fuels to record levels, and alternative sources of energy such as harvest slash were considered. Some studies were launched to in- vestigate the impact of slash removal, and the Canadian Forest Service fi nanced over many years the Energy from the Forest program (EN- FOR), a part of which was aimed at developing tools to defi ne sustainable levels of organic mat- ter and nutrient removal. So we already have a moderately abundant ecological knowledge, from our Canadian research base and also from research done in countries with similar forest and climatic conditions. We know that in most cases, whole-tree harvesting slightly acidifies the soil and reduces soil nutrient reserves, espe- cially calcium. We also know that for some site conditions and some tree species, it reduces tree productivity. Why is this good news? By knowing which sites and species are sensitive to intensive bio- mass removal, we can avoid it in these areas. At the same time we can be a little more confident that this practice is probably sustainable for the remaining sites and species. Of course, scientifi c knowledge is still in- complete. But the other good news is that the Canadian bioenergy sector is still nascent; al- though whole-tree harvesting is common, we are not yet intentionally chasing every twig and branch on a large scale in our forest to feed this industry. There is thus plenty of space to devel- op our understanding of ecological impacts, for example by establishing legacy fi eld trials com- paring the effects of different intensities of bio- mass removal on various ecosystem processes over different sites. This information can then be used to adjust the list of ‘no-go’ sites as new data accumulate. This way the expansion of our bioenergy industry can be tailored to fit the ecological sustainability of forest ecosystems, al- ways to the best of our knowledge. STAY TUNED… Of course, this is all easier said then done. But as they say, knowledge is power. That’s why in fu- ture columns we will discuss various issues related to the sustainability of forest biomass harvesting, and also have a look of what’s being done in other countries to tackle these issues. This will hopefully help draw the lines in grey areas, despite the uncertainties. • Evelyne Thiffault of Natural Resources Canada writes this regular column on the sustainability of biomass harvest- ing for Canadian Biomass on behalf of the Canadian Research Group on Ecosystem Sustainability. No.1 In The Forest 3-6 JUNE 2009 JÖNKÖPING, SWEDEN WWW.ELMIA.SE/WOOD OUT IN THE FOREST· NEWS · MEETINGS DEMO · MACHINES · TECHNOLOGY In cooperation with CanadianBIOMASS 9
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