Peatlands in the Earth’s 21st century climate system
2011
Frolking, Steve | Talbot, Julie | Jones, Miriam C. | Treat, Claire C. | Kauffman, J Boone | Tuittila, Eeva-Stiina | Roulet, Nigel
Peatlands occupy a relatively small fraction of the Earth’s land area, but they are a globally important carbon store because of their high carbon density. Undisturbed peatlands are currently a weak carbon sink (~0.1 Pg C y–¹), a moderate source of methane (CH₄; ~0.03 Pg CH₄ y–¹), and a very weak source of nitrous oxide (N₂O; ~0.00002 Pg N₂O–N y–¹). Anthropogenic disturbance, primarily agriculture and forestry drainage (10%–20% of global peatlands), results in net CO₂ emissions, reduced CH₄ emissions, and increased N₂O emissions. This likely changes the global peatland greenhouse gas balance to a C source (~0.1 Pg C y–¹), a 10% smaller CH₄ source, and a larger (but still small) N₂O source (~0.0004 Pg N₂O–N y–¹). There is no strong evidence that peatlands significantly contributed to 20th century changes in the atmospheric burden of CO₂, CH₄, or N₂O; will this picture change in the 21st century? A review of experimental and observational studies of peatland dynamics indicates that the main global change impacts on peatlands that may have significant climate impacts are (1) drainage, especially in the tropics; (2) widespread permafrost thaw; and (3) increased fire intensity and frequency as a result of drier climatic conditions and (or) drainage. Quantitative estimates of global change impacts are limited by the sparse field data (particularly in the tropics), the large variability present in existing data, uncertainties in the future trajectory of peatland use, interactive effects of individual impacts, and the unprecedented rates of climate change expected in the 21st century.
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