The role of forests in global carbon budgeting

Abstract

While forests have the capacity to sequester significant amounts of carbon, the natural and anthropogenic processes driving carbon fluxes in forests are complex and difficult to measure. However, since land use change is estimated to be the second largest source of carbon emissions to the atmosphere after the burning of fossil fuels, understanding and quantifying forest carbon sinks and sources is an important part of global carbon budgeting and climate change policy design. Although carbon emissions from land use change have remained fairly steady over the last few decades, there have been significant regional variations within this trend. Specifically, deforestation rates in the tropics, particularly in Asia, have grown significantly. In contrast, forests outside the tropics have been sequestering incremental carbon due to CO2fertilization and due to forest regrowth on lands that had been cleared for agriculture prior to industrialization. Land use change is widely considered the most difficult component to quantify in the global carbon budget. The underlying data is often incomplete and may not be comparable across countries or regions due to different definitions of forest cover and land uses. Deforestation rates in the tropics are particularly difficult to determine due to these factors as well as differences in the way land degradation, such as selective logging and fuelwood removals, are accounted for in national statistics.