Dan Blaustein-Rejto

Increased use of nitrogen fertilizer and other agricultural inputs is important for raising crop yields and meeting growing food demand, but risks increasing greenhouse gas emissions. We project net greenhouse gas emissions from crop production in Africa in 2050 under different scenarios of yield growth. We find that increasing yields would reduce emissions-even if it requires greater use of nitrogen fertilizer, fuel, and pesticides-primarily due to avoided cropland expansion. If Africa more than doubled yields from 2025 levels to meet future food demand while avoiding cropland expansion, an estimated 2.0 gigatons of carbon-dioxide equivalent per year in emissions could be avoided, equivalent to nearly 81% of all Africa’s emissions from agriculture, forestry, and land use in 2021.

Beef production accounts for the largest share of global livestock greenhouse gas emissions and is an important target for climate mitigation efforts. Most life-cycle assessments comparing the carbon footprint of beef production systems have been limited to production emissions. None also consider potential carbon sequestration due to grazing and alternate uses of land used for production. We assess the carbon footprint of 100 beef production systems in 16 countries, including production emissions, soil carbon sequestration from grazing, and carbon opportunity cost—the potential carbon sequestration that could occur on land if it were not used for production. We conduct a pairwise comparison of pasture-finished operations in which cattle almost exclusively consume grasses and forage, and grain-finished operations in which cattle are first grazed and then fed a grain-based diet. We find that pasture-finished operations have 20% higher production emissions and 42% higher carbon footprint than grain-finished systems. We also find that more land-intensive operations generally have higher carbon footprints. Regression analysis indicates that a 10% increase in land-use intensity is associated with a 4.8% increase in production emissions, but a 9.0% increase in carbon footprint, including production emissions, soil carbon sequestration and carbon opportunity cost. The carbon opportunity cost of operations was, on average, 130% larger than production emissions. These results point to the importance of accounting for carbon opportunity cost in assessing the sustainability of beef production systems and developing climate mitigation strategies.

The benefits of genetically engineered (GE) crops are systematically underestimated because previous studies did not incorporate the reduction in greenhouse gas (GHG) emissions associated with yield increases. We estimate this impact using the carbon opportunity cost of land use. Our results suggest that the GHG emissions reductions from the yield increases in GE crops are substantial and should be included in future analyses.