Beginning in the 1940s, the “green revolution” increased crop yields around the globe through seed hybrids, increased irrigation and new fertilizers and pesticides. The result was “agricultural intensification,” getting more grain from each acre of land. While the increase in productivity is unquestioned, drawbacks exist as well — negative environmental and health consequences from pesticide use, increased water demand, reductions in biodiversity and increased vulnerability to future famines.

A growing awareness of the causes and potential consequences of climate change have added another variable to the equation, however: As crop yields increase, the pressure to clear new lands could in part decrease; land that isn’t cleared can continue to sequester CO₂, one of the gases that contribute to climate change.

A 2010 Stanford University study published in the Proceedings of the National Academy of Science, “Greenhouse Gas Mitigation by Agricultural Intensification,” seeks to quantify the effects of higher crop yields on greenhouse gas emissions. The study’s findings include:

• Agricultural intensification has brought about greater net benefits than a system that focuses on expanding cropland with lower inputs to generate crops.
• Between 1961 and 2005, higher net crop yields avoided the emission of approximately 161 gigatons of carbon (GtC).
• Compared with the baseline technology in 1961, every additional dollar invested in agricultural yields has resulted in 68 fewer kilograms of carbon (kgC) emitted.

The authors find that investment in agriculture innovations and helping ensure that virgin land remains uncleared provide superior results to other GHG mitigation strategies. The challenge is in balancing local needs and global benefits: “Choices are made locally and are influenced by local and regional food security, transportation costs, labor, poverty and technology rather than global atmospheric carbon,” the authors state, suggesting that “private and multilateral investments should focus on maintaining or restoring tropical forests and increasing yields through low petroleum inputs on existing cropland.”

A related 2009 report, “Failure to Yield,” looks at the potential of both genetically engineered seeds and traditional breeding methods in increasing crop yields.

Tags: carbon, global warming, greenhouse gases

By Leighton W. Klein | November 29, 2010