The First State of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle

PB 103 The six chapters (Chapters 10-15) in Part III consider the current and future carbon balance of terrestrial and aquatic ecosystems in North America. Although the amount of carbon exchanged between these ecosystems and the atmosphere each year through photosynthesis and plant and microbial respiration is large, the net balance for all of the ecosystems combined is currently a net sink of 370-505 million tons of carbon (Mt C) per year1. This net sink offsets only about 2030% of current fossil-fuel emissions from the region (1856 Mt C per year in 2003) (Chapter 3 this report). The cause of this terrestrial carbon sink is uncertain. Although management has the potential for removing carbon from the atmosphere and storing it in vegetation and soil, most of the current sink is not the result of current management practices. Instead, most of it may be attributed to a combination of past management and the response of terrestrial ecosystems to environmental changes.