There have been some recent articles about how climate change is harming agriculture. One by Kim Severson in the New York Times (here) says “Drop a pin anywhere on a map of the United States and you’ll find disruption in the fields.” It goes on to discuss the impacts on “11 everyday foods”: tart cherries (Michigan), organic raspberries (New York), watermelons (Florida), chickpeas (Montana), wild blueberries (Maine), organic heirloom popcorn (Iowa), peaches (Georgia and South Carolina), organic apples (Washington), golden kiwi fruit (Texas), artichokes (California), and rice (Arkansas).
Well, that is a sampling of foods from around the country. I’m not so sure how “everyday” many of them are, but rice is certainly one of the basic grains.
A somewhat more convincing article by Chris McGreal in The Guardian interviewed farmers in valley of the Missouri River near Langdon, in northwestern Missouri. These are corn and soybean farmers. Their problem has been moisture: they have had too much rain. In many years, the ground has been so muddy that crops were ruined or not planted at all. In other years, the rain has caused the water table to rise so much that the ground looks dry on top, but is mucky mud just a few inches down. This is something, of course, that would affect river valleys the most, and the big river valleys in Missouri are some of the richest farmland the state has.
Most climate change studies project that climate change will impact agriculture negatively. Given this blog’s focus on the large statistical perspective, I thought it might be interesting to see how crop yields are doing in Missouri. The United States Department of Agriculture publishes the data. This data is a statistical average of yields across Missouri. Results in any one location may be different.
Figure 1 shows the per-acre yield for corn. The data shows that corn yields vary significantly from year-to-year, and that some years are really terrible, with yields being roughly half of what they are in good years. That said, there is a clear trend toward increased yields from 1957 right through 2014. Yields since then have been lower, and it is possible that we are looking at the start of a downward trend, but 4 years is not sufficient to tell.
Figure 2 shows the per-acre yield for soybeans. The yearly variation here may be somewhat less, but the overall pattern is much the same. With soybeans, however, yields increased right through 2017.
This data doesn’t tell us why crop yields are rising. Perhaps they are due to improved farming practices and better seed stock. It is possible that warmer temperatures, an increase in carbon dioxide, and more rain have benefitted crop yields overall, even if they have hurt some farmers in some locations. We just don’t know, at least not from this data.
What we do know is that, overall, the predicted negative effects of climate change do not yet seem to be reducing yields in these two important crops.
McGreal, Chris. 2018. “As Climate Change Bites in America’s Midwest, Farmers Are Desperate to Ring the Alarm.” The Guardian,” 12/12/2018. Viewed online 5/1/2018 at https://www.theguardian.com/us-news/2018/dec/12/as-climate-change-bites-in-americas-midwest-farmers-are-desperate-to-ring-the-alarm.
Severson, Kim. 2019. “From Apples to Popcorn, Climate Change Is Altering the Foods America Grows.” The New York Times, 4/30/2019. Viewed online 5/1/2019 at https://www.nytimes.com/2019/04/30/dining/farming-climate-change.html?rref=collection%2Fsectioncollection%2Fclimate&action=click&contentCollection=climate®ion=rank&module=package&version=highlights&contentPlacement=2&pgtype=sectionfront.
National Agriculture Statistics Service, United States Department of Agriculture. Quick Stats. This is a data portal that can be used to build a customized report. I focused on yield, in bushels per acre, for corn and soybeans from 1957-2018. Data downloaded 5/1/2019 from https://quickstats.nass.usda.gov.