Corn's Troubled Future Under Climate Change

There's something horribly ironic about the recent report from Environment America that suggests American corn yields will decline 3 percent in coming years due to anthropogenic global warming.

The report itself is bad news.

It suggests that contrary to much-ballyhooed studies and predictions that American crop yields will increase due to a longer growing season and the carbon fertilization effect, which increases crop growth due to greater atmospheric carbon for plants to feed on, American corn farmers in coming years will lose over a billion dollars in revenue annually as irregular precipitation and overly-warm temperatures stunt crop growth.

Iowa stands to lose $249 million yearly; Illinois, $243 million; Nebraska, $163 million.

(Like other studies predicting the effects of global warming on agriculture, "Hotter Fields, Lower Yields" doesn't attempt to account for increased risks of pest attacks, extreme weather events, or plant disease, all of which will radically increase as the climate warms)

The irony is that corn, or at least most American corn, is a major contributor to greenhouse gas emissions. That's because maize is a particularly nitrogen-leaky plant, as it has quite shallow roots, and only uses nitrogen located in the top inch of soil. It also only takes up nitrogen for 60 days of the year.

Studies recently carried out by the International Council for Science suggest that between 4 and 5 percent of nitrogen fertilizer becomes nitrous oxide and enters the atmosphere. Previous estimates had put the number at 1 percent. This means that studies assessing the GHG emissions from industrial agriculture, which uses vast amounts of nitrogen fertilizer, have probably underestimated its contribution to climate change.

The second irony is that although industrially-cultivated maize may generally be a nitrogen-leaky plant, it doesn't have to be.

In rural Mexico, where it was originally cultivated, maize is inter-planted with teosinte, its wild progenitor, squash, and nitrogen-fixing beans, in the milpa, the Mexican corn-patch, which prevents the immense nitrogen leakage associated with growing corn on vast tracts of land, spanning hundreds or thousands of acres.

There is massive genetic diversity among corn crops — there are probably more varieties grown in Oaxaca than in the entire United States. There's even one sub-species that fixes its own nitrogen, thereby avoiding the nitrogen leakage that contributes to emission growth.

Furthermore, some corn varieties show extreme resistance to drought. Tripsacum, a relative of corn which can interbreed with maize, "is adapted to a wide range of soil and climatic conditions and shows resistance to heat stress, drought, water-logging, and certain foliar diseases and insect pests," according to Mexican agronomist Alejandro Nadal. A breed of teosinte harbors genes resistant to seven of the nine major diseases that afflict American corn crops.

So we're doing all we can to conserve the wild Mexican landraces that could replace American varieties as their yields decline and they become sick with blight or ravaged by pests, right? It would be nice if we were.

Instead, the future of corn production will be caught in an increasingly destructive cycle.

NAFTA laid the groundwork, removing the tariffs that had previously protected the Mexican farming industry, and forcing Mexican farmers to compete with heavily subsidized American industrial agro-plantations. It set off a massive increase in migration from rural Mexico to urban centers, and then from urban centers to the United States.

So far, this hasn't affected maize production numbers, but, as Nadal and researcher Tim Wise put it:

"It is difficult to believe that such large-scale migratory trends will not eventually translate into losses in maize production, local knowledge, and maize diversity."

Indeed, of the Rural Production Districts, the artificial districts created by the Mexican government for statistical counting purposes, the ones with the highest levels of seed diversity have seen "net out-migration for migratory patterns within Mexico," probably because farmers are moving initially to horticulture fields, then on to the United States.

On top of that, global warming will also have a massive, corrosive effect, more cyclical in nature: first, global warming, largely caused by industrialized societies, including industrial agriculture, damages industrial agricultural systems. Mexico, closer to the equator, will see its agricultural production fall by 30 to 35 percent.

The availability of hybrids and new seed-stock that could lessen the impact of climate change on both American and Mexican maize production will decrease, as part and parcel of that very climate change. The result? Less potential resilience, which seems like a pretty bad outcome given that resilient seed-stock is precisely what we'll need as climate change continues.

The solutions aren't easy: slow down, and then stop, global warming, and make sure Mexican corn farmers can survive and prosper, probably by renegotiating or repealing NAFTA. That doesn't mean they should be off the agenda.

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