Carbon balance on federal forest lands of Western Oregon and Washington: The impact of the Northwest Forest Plan

The management of federal forest lands in the Pacific Northwest (PNW) region changed in early 1990s when the Northwest Forest Plan (NWFP) was adopted with the primary goal to protect old-growth forest and associated species. A major decline in timber harvest followed, extending an earlier downward trend. The historic and projected future change in carbon (C) stores and balance on federally managed forest lands in Western Oregon (OR) and Western Washington (WA) was examined using the IANDCARB 3.0 simulation model. The projections include C stores on-site, in harvested wood products and disposal and reflect a set of contrasting visions of future forest management in the region formulated as five alternative management scenarios that extend to year 2100. A significant and long-lasting net increase in total C stores on federal forest lands relative to early 1990s level was projected for both OR and WA under all examined management scenarios except the Industry Scenario which envisioned a return to historic high levels of timber harvest. In comparison with the Industry Scenario, the low levels of timber harvest under the NWFP between 1993 and 2010 were estimated to increase total C stores by 86.0 TgC (5.1 TgC year(-1) or 2.16 MgC ha(-1) year(-1)) in OR; in WA the respective values were 45.2 TgC (2.66 TgC year(-1) or 1.33 Mg Cha(-1) year(-1)). The projected annual rate of C accumulation, reached a maximum between 2005 and 2020 approaching 4 TgC year(-1) in OR and 2.3 TgC year(-1) in WA, then gradually declined towards the end of projection period in 2100. Although not the original intent, the NWFP has led to a considerable increase in C stores on federal forest lands within the first decade of plan implementation and this trend can be expected to continue for several decades into the future if the limits on timber harvest set under the NWFP are maintained. The primary goal of the NWFP to protect and restore old-growth forest may take several decades to achieve in WA whereas in OR the area protected from clearcut harvest may be insufficient to meet this goal before the end of projection period in 2100. (C) 2012 Elsevier B.V. All rights reserved.