Simulations of forest system response and feedbacks to global change: experiences and results from the US Country Studies Program

Large shifts in the response and feedbacks of forest systems are implied by models and systems analysis driven by global change scenarios of general circulation models (GCMs). Prior climate change analyses and modeling efforts have been reported at a global scale in a few developed countries, but relatively few national assessments have been successfully completed in developing countries. Under the auspices of the U.S. Country Studies Program, analysts from 55 countries employed a common set of methods and models to characterize current carbon (C) pools in forests, future impacts of global change on forest distribution, and management options for conserving and sequestering carbon dioxide (CO2) in forest systems. The analysis revealed that the response and feedbacks of forest systems to global climate change will be profound in the 55 countries studied on five continents. Globally, forest vegetation and soils contain about 1146 Pg C, with approximately 37% of this C in low-latitude forests, 14% in mid-latitudes, and 49% at high latitudes. The impacts of future global change on forest distribution and productivity will be most significant at high latitudes, with more modest changes in distribution and productivity at low latitudes. Future opportunities to conserve and sequester CO2 in forest systems are potentially significant, but land-use practices and global change will influence the size of this C pool and CO2 sink. In the future, a greater proportion of forests at all latitudes could become a greenhouse gas (GHG) source if sustained management and conservation policies are not employed. The timing and magnitude of future changes in forest systems are dependent on global environmental factors (for example, global change, biogeochemical Sulphur and Nitrogen cycles), as well as on human factors such as demographics, economic growth, technology, and resource management policies. (C) 1999 Elsevier Science B.V. All rights reserved.