News Date: 06/22/2010
A joint study between Stanford University and the Carnegie Institution of Washington, accepted May 4 by the Proceedings of the National Academy of Science, concludes that despite higher emissions due to sources such as increased fertilizer and pesticide use, higher-yield crops have resulted in a net decrease in greenhouse gases (GHG’s) released into the atmosphere.
Between 1961 and 2005, the world’s population more than doubled, from slightly over 3 billion people to about 6.5 billion. At the same time, agricultural production increased by 162%. The dilemma presented is that with constant yield, as agricultural production increases, more land must be devoted to agriculture. However, during that same period, global cropland only grew by 27% while crop yields increased by 135%. This yield increase avoided the need for large deforestation, often a source of considerable emissions itself due to machinery and/or burning forest areas.
To evaluate the effects of the increase in yield with respect to the effects of a simple increase in agriculturally-devoted land, the researchers created hypothetical “alternative world” scenarios to which they compare the real world calculated GHG emissions from 1961-2005.
Alternative World 1 (AW1) assumes that the world evolved in every aspect exactly the same as the real world, except that agriculture technology remained as it was in 1961. The primary issue with AW1 is how to replicate the 2005 standard of living with 1961 agriculture, and the corresponding cost in terms of GHG emission. AW1 is thus the upper estimate of GHG emissions.
Alternative World 2 (AW2) maintains the standard of living from 1961 with pre-1961 fertility and mortality rates, and is thus a lower estimate of the GHG emissions without the advances made in agricultural yield. Interesting to note is that AW2 “coincidentally result(s) in very similar year 2000 populations albeit with different age structures.”
Scenario 1 results in the world’s dedicated cropland nearly tripling since 1961, adding approximately 7 million square miles to the existing 3.7 million square miles. This totals 5.8 million square miles more than the total farmland in 2005, and accounts for approximately 92% of the world’s arable land. The result is that the real world yield gains avoided approximately 34% of the emissions between the Industrial Revolution (1850) and 2005.
In scenario 2, there is less of an increase in cropland, but agriculture accounts for a 4.3 million square miles increase, compared to the real world 1 million square miles increase. The overall emission avoidance is approximately 18% of emissions between 1850 and 2005, or roughly half of the impact of AW1.
Overall, the crop yield improvements from 1961-2005 have prevented between 317 and 590 billion tons of GHG’s from being emitted into the atmosphere. By 2050, the world’s population is expected to reach 8.9 billion accompanied by a 70% rise in food demands. Even with smaller crop yield gains than the 1990’s, there is still potential to avert significant GHG emissions. (By: Jason Markovich, Contact: Nathan Bowen)
Sign up here to receive NASDA News.