"Fossil fuels’ biggest impact on the agricultural sector stems from the use of natural gas in industrial fertilizer production. Industrial fertilizer was first mass-produced in 1914 using what came to be known as the . This invention enabled the , a boom in agricultural production that took place in the latter half of the 20th century, starting in Mexico and India. From 1961 to 2010, cereal yields per acre increased by 217 percent in Mexico and 183 percent in India. It is no coincidence that the human population has more than quadrupled since 1920. We often attribute the Green Revolution to the spread of high-yielding crop varieties. Yet these varieties typically require industrial fertilizer application. The Haber-Bosch method, combined with mechanization and pesticides derived from fossil fuels, [has] represented a massive and unsustainable injection of fossil fuels into our food system. Today, the production of one food calorie in the United States requires 2.7 fossil fuel calories."