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Forests potentially contribute to global climate change through their influence on the global carbon (C) cycle. They store large quantities of C in vegetation and soil, exchange C with the atmosphere through photosynthesis and respiration, are sources of atmospheric C when they are disturbed, become atmospheric C sinks during abandonment and regrowth after disturbance, and can be managed to alter their role in the C cycle. The world's forest contain about 830 Pg C (1015 g) in their vegetation and soil, with about 1.5 times as much in soil as in vegetation. During the 1980s, analysis of C budgets show that forest of the temperate and boreal countries were a net sink of atmospheric C of about 0.7 Pg yr-1, but the tropics were a net source of about 1.6 Pg yr-1. However, accounting for the imbalance in the global C cycle suggests that forest are not significantly contributing to the net increase in atmospheric CO2 and thus not contributing to global climate change. However, this may not continue into the future as temperate and boreal forests reach maturity and become a smaller C sink, and if rates of tropical deforestation and degradation continue to accelerate. Recent studies suggest that there is the potential to manage forests to conserve and sequester C to mitigate emissions of carbon dioxide by an amount equivalent to 11-15% of the fossil fuel emissions over the same time period. Aggressive adoption of these forest management options are necessary to prevent forests becoming a significant net source of CO2 to the atmosphere in the future and contributing to climate change.
