The collapse of the American coal industry is having major benefits for the nation's health, but it's also having a less-heralded effect: it's boosting crop yields and making food prices cheaper.
Coal burning is a major contributor to air pollution, which causes an estimated 3-9 million deaths a year worldwide. Among the pollutants are nitrogen oxides, particularly from coal plants, which react in sunlight with other molecules to produce ozone. Although the shield of all life on Earth in the stratosphere, close-to-ground-level ozone is harmful both to animals and plants, accounting for an estimated 90 percent of air pollution's effects on crop yields.
The damaging effect of low-atmosphere ozone on human lungs has been incorporated into estimates of pollution's costs, but the impact on crops has been largely ignored. A paper in the American Journal of Agricultural Economics sets out to address this, examining the benefits of declining ozone on two of America's largest crops as coal use declined from 2003-2013.
Inevitably the picture varies by location – some farms are still exposed to as much ozone as they ever were, while others were always too far away to be affected much. However, by combining the entire farm belt, first author Dr Konstantinos Metaxoglou of MIT concludes corn yields rose 2.5 percent as a result of coal plant closures, while soybean production increased 1.6 percent.
Those sound like small effects, but the scale of these crops means the economy benefited by $1.6 billion every year. Plenty more coal plants have shut down since the end of Metaxoglou's study period, so must now be considerably larger.
Corn farmers downwind of shuttered power stations gained 7 percent in production and would have been the prime beneficiaries. However, Metaxoglou calculates overall the falling prices caused by the increased supply meant farmers actually lost money. Consumers, however, now had access to cheaper food.
Corn and soy are included in so many processed foods, far beyond the obvious tortillas and tofu, that the effect would be exceptionally dispersed. Consumers wouldn't have noticed the fall (or slower rise) in the price of their groceries as a result of this effect, but that doesn't mean it wasn't there every time they reached the till.
“Our findings show that reducing NOx and other harmful emissions from power plants is beneficial not only for human health, but also for agriculture production,” Metaxoglou said in an emailed statement.
Around half of coal's decline has been from competition with gas, but the other half is a result of rising solar and wind production. Opponents of climate action love to bemoan the effect of renewable energy subsidies on poorer consumers' electricity bills, but all that cost and more comes back in less obvious ways.