Advancing climate change and a rapidly growing global population—projected to reach about 9 billion by mid-century—will increasingly challenge the capacity of societies, their land and other natural resources, to produce enough food. Agricultural ecosystems will need to be more productive and more resilient in the face of drought and other environmental stresses, while reducing greenhouse gases (GHGs) and other environmental impacts. Two important considerations are crop yields and nitrogen fertilizer use, both of which are associated with production of GHGs. We considered and compared the prospects of crop improvement methods (especially genetic engineering and classical plant breeding) and agroecological and other farm-based methods to significantly raise crop yields and reduce nitrogen pollution. To provide a preliminary quantification of the record of these technologies and practices over the past several decades and a reasonable expectation of their prospects for the near future, we reviewed experimental field trial records for engineered crops and other public records for yield, nitrogen use efficiency (NUE), and experimental genes. We also compared apparent genetic potential for classical breeding and genetic engineering for improving NUE, and considered genetic and physiological challenges for breeding and engineering in coming years, including pleiotropic effects associated with crop improvement.
Results/Conclusions
We found that while engineered corn in the United States has increased yield since 1996 by about 3 to 4 percent, breeding and other methods have increased yield by about 28 percent. Engineered genes have not increased yield in soybeans, while other methods have increased yield by about 16 percent. We found no commercial engineered crops for improving NUE, while breeding and other methods have improved nitrogen use efficiency by about 20 to 40 percent in several major crops. Of 1,108 field trials for yield-related engineered genes since 1987, and 125 for nitrogen use efficiency, two classes of insect resistance and herbicide tolerance genes have been successfully commercialized. The findings suggest that plant breeding and improved farming methods, including those based on agroecological principles, hold the greatest promise for meeting food demand and climate challenges, and that a shift in research and policy emphasis toward these methods is warranted.