Localized erosion affects national carbon budget

Abstract

Small mountainous rivers discharge disproportionate amounts of sediment and carbon to then Earth's oceans. Our New Zealand data demonstrates that localized erosion plays a greater role in C budgets than has been recognized in national and global studies. We estimate that New Zealand's rivers export 4 ± 1 Mg C km-2 2 yr-1 of dissolved organic carbon (DOC) and 10 ± 3 Mg C km-2 yr-1 of particulate organic carbon (POC) (2 and 6 times the global average), which is equivalent to 40% of New Zealand's fossil fuel emissions. Under intact native vegetation in mountain-belt hot spots, POC export greatly exceeds CO2 consumption from mineral weathering. Moreover, deforestation of fertile steepland greatly accelerates POC loss, evidenced by 1.7% of New Zealand's land area which generates 20% of exported POC. Thus, localized erosion deserves increased attention in C budgets and accounting. Copyright 2006 by the American Geophysical Union.