FORESTS FOR CARBON SEQUESTRATION OR FOSSIL-FUEL SUBSTITUTION - A SENSITIVITY ANALYSIS

Among the proposals for mitigating the increase of atmospheric CO, are the possibility of reforesting degraded lands to sequester C or of us ing sustainable forest harvests to displace fossil fuels. Storing C on -site in forests and harvesting forests for a sustainable flow of fore st products are not necessarily conflicting options if we recognize th at their relative merits in mitigating net emissions of C will depend on site-specific factors, such as forest productivity and the efficien cy with which harvested material is used. Since the land available for reforestation or development of forest plantations is limited, the re lative merits of the different mitigation strategies need to be consid ered. We use a mathematical model of C stocks and flows to compare the net effect on C emissions to the atmosphere for the two approaches ov er a range of values of forest productivity and the efficiency of prod uct use. When sustainably-produced forest products are used inefficien tly to displace fossil fuels, the greater C benefit is achieved throug h reforestation and protection of standing forests, and increasing the rate of stand growth yields little gain. However, when forest product s are used efficiently to displace fossil fuels, sustainable harvest p roduces the greater net C benefits, and the benefit increases rapidly with increasing productivity. (C) 1998 Elsevier Science Ltd.