Volume 15, Number 34: 22 August 2012
In an invited editorial in the journal Global Change Biology Bioenergy, Schulze et al. (2012) set the stage for their analysis of this important question by writing that "climate change impacts resulting from fossil fuel combustion challenge humanity to find energy alternatives that would reduce greenhouse gas (GHG) emissions." And one of the strategies that they indicate could substantially diminish our dependence on fossil fuels without competing with food production is the use of bioenergy obtained from forests, either by direct combustion of wood or its conversion to cellulosic ethanol. However, they say "there are important questions about GHG reduction, economic viability, sustainability and environmental consequences" that are associated with this strategy; and they go on to discuss them in some detail.
First of all, the five scientists - hailing from Austria, France, Germany, Switzerland and the United States - argue that "such an increase in biomass harvest would result in younger forests, lower biomass pools, depleted soil nutrient stocks and a loss of other ecosystem functions," such that "the proposed strategy is likely to miss its main objective, i.e. to reduce GHG emissions, because it would result in a reduction of biomass pools that may take decades to centuries to be paid back by fossil fuel substitution, if paid back at all." In the long run, therefore, they feel that "depleted soil fertility will make the production unsustainable and require fertilization, which in turn increases GHG emissions due to N2O emissions," which ultimately makes the large-scale production of bioenergy from forest biomass, in their opinion, "neither sustainable nor GHG neutral."
A reasonable alternative, in Schulze et al.'s opinion, would be the "afforestation of lands that once carried forests," which they say would allow existing forests to continue to provide a range of ecosystem services. Yet, "on arable or pasture land," as they continue, "such a strategy would compete with food and fodder production." And, hence, they caution that society should fully quantify direct and indirect GHG emissions associated with energy alternatives and associated consequences prior to making policy commitments that have long-term effects on global forests; for they ominously warn "there is a substantial risk of sacrificing forest integrity and sustainability for maintaining or even increasing energy production with no guarantee to mitigate climate change." Or as we once warned in one of our own editorials (15 May 1999), it is extremely important that we do not get the regulatory cart before the scientific horse.
Sherwood, Keith and Craig Idso
Reference
Schulze, E.-D., Korner, C., Law, B.E., Haberl, H. and Luyssaert, S. 2012. Large-scale bioenergy from additional harvest of forest biomass is neither sustainable nor greenhouse gas neutral. Global Change Biology Bioenergy: 10.1111/j.1757-1707.2012.01169.x.