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Terrestrial ecosystems, comprising vegetation and soil in uplands and wetlands, significantly impact the global carbon (C) cycle and, under natural conditions, are a sink of atmospheric carbon dioxide (CO₂) and methane (CH₄). However, conversion of natural to managed ecosystems (i.e., agroecosystems, urban lands, and mined lands) depletes ecosystem C stocks, aggravates gaseous emissions, and exacerbates radiative forcing. Thus, the onset of agriculture around 8000 BC presumably transformed these sinks into a source of greenhouse gases (GHGs) (Ruddiman 2003), mostly CO₂, CH₄, and nitrous oxide (N₂O), and depleted the terrestrial (soil, vegetation, and peatlands) C stocks. Ruddiman (2005) estimated the depletion of the terrestrial C stock (soil and vegetation) by 456 Pg (502.65 × 10⁹ tn) since the onset of agriculture. Of this, the historic depletion of soil organic carbon (SOC) stock is estimated at …