Methane and nitrous oxide emissions from land

Accumulation of the greenhouse gases carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in the Earth's atmosphere, resulting from human activities, is responsible for recent global heating and associated climate change. Natural soil emissions of CH4 and N2O are substantial, and increase after land conversion to agriculture, e.g., flooded rice fields release CH4 and manures and synthetic nitrogen fertilizers promote the release of N2O. Some mitigation of N2O emission is achievable by improved nitrogen use efficiency. Replacement of fossil fuels by crop-based biofuels is controversial, because reduced CO2 emissions can be largely offset by increases in those of N2O.