Effects of Land Use and Climate on Ecosystem Carbon Balance from a Recent National Assessment

Abstract:

A recent ecosystem carbon sequestration assessment estimated that the conterminous United States (CONUS) stored 48.3 Pg of carbon, or 6.14 Kg of carbon per square meter covering all vegetated as well as arid lands in the 48 states. The CONUS is shown to be a strong C sink with an average rate of 431 Tg of carbon up-take per year (ranging from 148-667 TgC/yr) for the first half of 2000s as a baseline. Dissolved carbon transported through aquatic systems and emitted carbon dioxide from water surfaces averaged 142 Tg per year. Emissions from wildfires averaged 14 Tg per year based on a separate analysis using remotely sensed fire areas and burn severities. Wildfires are simulated under future climate scenarios and are projected to increase in area, intensity and emissions in future years. Under combinations of future land use/land cover change and climate scenarios, the net ecosystem carbon balance is projected to remain as a carbon sink for the CONUS but could become weaker by 2050 as compared to the baseline, ranging from 44-579 TgC per year. However, a separate analysis of the assessment noted that future potential rate of carbon sequestration by CONUS ecosystems could be higher (increasing to 503-676 Tg of carbon per year by 2060, depending on climate scenarios) than the present rate. This assumes the ecosystems would be managed with active fire suppression, maintained for natural vegetation cover, and benefited from increased water use efficiency of increased atmosphere carbon dioxide concentration.