Potential carbon dioxide emission reductions from avoided grassland conversion in the northern Great Plains.

Protection of lands threatened with conversion to agriculture can reduce carbon emissions. Until recently, most climate change mitigation incentive programs for avoided conversion have focused on forested ecosystems. We applied the Avoided Conversion of Grasslands and Shrublands v.1.0 ( ACo GS) methodology now available through the American Carbon Registry to a threatened region of grasslands in the northern Great Plains. For all soil types across 14 counties in North and South Dakota, we used the DAYCENT model calibrated to the study area to quantify the difference in CO₂ and N₂O emissions under a cropping and a protection scenario, and we used formulas in the ACo GS methodology to calculate CH₄ emissions from enteric fermentation under the protection scenario. We mapped the resulting GHG emissions across the entire project area. Emissions averaged 51.6 tCO₂e/ha over 20 years, and with a 31% reduction for leakage and uncertainty from the ACo GS methodology, carbon offsets averaged 35.6 tCO₂e/ha over 20 years. Protection of 10% of the 2.1 million unprotected ha in the project area with the highest emissions would reduce emissions by 11.7 million tCO₂e over 20 years (11% of the total emissions from all unprotected grassland) and avoid a social cost of $430 million worth of CO₂ emissions. These results suggest that carbon offsets generated from avoided conversion of grasslands can meaningfully contribute to climate mitigation and grassland conservation objectives. [ABSTRACT FROM AUTHOR]