Trends in management of the world's forests and impacts on carbon stocks

摘要

Global forests are increasingly affected by land-use change, fragmentation, changing management objectives, and degradation. In this paper we broadly characterize trends in global forest area by intensity of management, and provide an overview of changes in global carbon stocks associated with managed forests. We discuss different interpretations of "management" and highlight some important accounting and analysis issues. The area of global forests has declined by 3% since 1990 but the area of planted forest has increased in all regions of the world and now accounts for almost 7% of global forest land. The area of primary forest, which is typically defined as lacking direct human influence, is about 34% of all forest land according to country reports, but the area is declining especially in South America and Africa because of human-caused habitat fragmentation and degradation. Concurrently, the area of naturally regenerated forest that is not classified as primary forest has declined. As a result of increasing management intensity, the area of unmanaged forest, typically defined as land lacking protected status or a management plan, dropped significantly since 1990 and now comprises only 21% of global forests. There have been significant increases in areas of forest used for non-wood forest products such as protection of soil and water, conservation of biodiversity, and provision of social services. Globally, timber production has been relatively stable since 1990, but increasing areas of forest used for non-wood forest products indicates that harvesting is taking place on a smaller proportion of the total forest area. Based on trends in the area of managed forest and regional studies, it is clear that historical and current forest management has been a very significant determining factor of current carbon stocks. Established forests currently offset about 30% of global emissions of CO2 from fossil fuel use, and there are mitigation opportunities involving forests that could increase the gross terrestrial C uptake from roughly 4.0 to 6.2 Pg C annually, However, our results suggest that a diversifying use of forest land may have significant consequences for maintaining or increasing the current rate of terrestrial carbon sequestration. In the future, indirect human influences such as increasing atmospheric CO2 and climate change, along with the direct effects of land management and projected increasing demand for wood biofuel, are likely to become increasingly important elements that influence land management strategies and the role of forests in the global carbon cycle. Published by Elsevier B.V.