According to a recent review of studies, US cropland has expanded anywhere from one to seven million acres over the past 17 years (Austin, Jones, et al., 2022). However, USDA cropland estimates* provide a somewhat different picture:

Not so bleak, at least from the perspective of protecting wild habitat and grasslands from agricultural encroachment, the better to restore biodiversity and keep carbon out of the atmosphere. Then again, the above chart makes the decline in cropland look bigger than it has been, which was just 5% over a period of 20 years. We can do better. Unfortunately, the federal government’s Renewable Fuels Standard (RFS) undermines efforts to shrink US cropland further by subsidizing farmers to grow biofuel crops - mainly corn for ethanol - to meet biofuel mandates for transportation and heating fuel. Check out the next chart and guess the year RFS went into effect:

That would be 2006, or almost 10 million additional acres of corn ago. Now, nearly 40% of corn grown in the US goes to ethanol, up from 5% in 1996 (Saavoss et al, 2021).

The good news is that corn farm productivity has been improving at an average rate of 1.2% per year for a few decades, an improvement associated with economies of size and seen mostly in farms between 750 and 1,500 acres. On these larger farms, an acre of land grows more corn than it used to, so there’s less need to expand cropland to increase yield. And there’s plenty of room for further productivity gains, given that 58% of total planted corn acres has been on farms of fewer than 750 acres (Saavoss et al, 2021). For the sake of the biosphere, it’s time for the small fry to sell or merge with other farms to increase the number of big farms.

Consolidation would allow the remaining farmers to benefit from the size advantage, which includes generating sufficient revenue to invest in precision technology tools. These tools lower costs, increase productivity, and help protect water, soil, air, and life by decreasing the amount of water, chemicals, fuels and fertilizer needed to grow crops (Saavoss et al, 2021).

Take crop productivity improvements and ample use of precision technology, add in conservation tillage, cover crops, and increased energy efficiency along the ethanol supply chain, and the “carbon intensity” of corn-based ethanol may be as much as 46% lower than the average carbon intensity of neat gasoline (Scully et al, 2021). That’s a good thing, but it’s still more CO2 in the atmosphere. Hopefully, we can transition to electric vehicles and net-zero energy sooner rather than later and finally wean US corn farmers off their dependence on biofuel subsidies. Only then will the conversion of undomesticated land into corn crops stop and very likely reverse, as much of this land is suboptimal for growing corn and wouldn’t be worth the trouble to farm without subsidies.

One more excerpt to wrap things up:

Recent expansion of croplands in the United States has caused widespread conversion of grasslands and other ecosystems. Here we assess annual land use change 2008–16 and its impacts on crop yields and wildlife habitat. We find that croplands have expanded at a rate of over one million acres per year…Our findings demonstrate a pervasive pattern of encroachment into areas that are increasingly marginal for production, but highly significant for wildlife, and suggest that such tradeoffs may be further amplified by future cropland expansion. Overall, the highest rates of loss of natural landcover relative to its remaining area occurred in swaths of the western Corn Belt and western Plains, where rates of existing cultivation and cropland expansion were both high (Lark, Spawn, Bougie, et al., 2020).

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* USDA provides annual estimates of total US cropland. Final figures for each year are available in USDA Statistical Bulletins.

References:

Austin, K. G., J. P. H. Jones, et al. (2022). "A review of domestic land use change attributable to U.S. biofuel policy." Renewable and Sustainable Energy Reviews 159: 112181. https://doi.org/10.1016/j.rser.2022.112181

Lark, T.J., Spawn, S.A., Bougie, M. et al. Cropland expansion in the United States produces marginal yields at high costs to wildlife. Nature Communications 11, 4295 (2020). https://doi.org/10.1038/s41467-020-18045-z

Scully, M. J. et al (2021) Carbon intensity of corn ethanol in the United States: state of the science. Environmental Research Letters. 16:4 043001 https://iopscience.iop.org/article/10.1088/1748-9326/abde08/meta

“Trends in Production Practices and Costs of the U.S. Corn Sector” - Economic Research Service/USDA, July 2021. Authors: M. Saavoss, T. Capehart, W. McBride, and A. Effland. https://www.ers.usda.gov/webdocs/publications/101722/err-294_summary.pdf?v=1601.4