Ozone is trimming farmers’ revenue by stealth

Fresh research suggests air pollution’s already major impact on crop yields is being compounded by global warming. How should the industry respond?

Throughout much of the Northern Hemisphere, urban dwellers must have wished they’d been out of town during this summer’s heatwave. But the consequences of climate change have been painfully evident for country folk as well, starting with farmers. Drought messed up maturation patterns and dampened yields; wildfires destroyed forests and fields. All the while, however, crops also faced aggression from a less visible enemy: air pollution.

Environmental authorities have long tracked ozone concentration in the atmosphere. Yet, so far, how much of it got into plants – and what effect it had on their development – remained moot. A study released this month quantifies the problem, and its findings make for uncomfortable reading. Led by the UK’s Centre for Ecology & Hydrology, the paper estimates that ozone pollution costs the world up to 227 million tons a year in yield for four main crops. Effects are particularly pronounced for soybean and wheat, with average yield losses of 12.4 percent and 7.1 percent respectively.

The problem is only getting worse. In part, this is because of worsening pollution in the very regions where growing populations demand greater food production: losses climb to 15 percent in large wheat-producing areas of China and India. But it is also because coping with climate change, perversely, makes plants more likely to absorb air pollution. Professor Gina Mills, of the CEH, told us that greater irrigation – hard to avoid in times of drought – opens pores on the plant’s surface, letting more ozone in and hurting yields further.

So far, little is done to mitigate the damage. “Most farmers are not really aware because you can’t actually see ozone pollution. What’s happening is that crops are growing less well and producing fewer seeds, but they can’t see the cause of that,” Mills said. The authors’ main aim is to put the problem on the industry’s radar – on a par with other risk causes, since the scientists deem its effects similar in magnitude to drought, heat or nutrient stress.

In the long run, obviously, the onus must be on reducing air pollution. In that respect, the Environmental Protection Agency’s decision this month not to weaken Obama-era ozone standards in the US sends the right signal.

But many farmers can’t really afford to wait until the problem is cleared. So, Mills advocates for shorter-term fixes. One of them is helping farmers select ozone-resistant seeds by screening crops for low sensitivity and carrying out trials with different irrigation patterns. For example, the CEH is currently exposing African crops to ozone levels met south of the Sahara to help pick up the sturdiest ones. Most important is designing the right crops in the first place: when breeders develop new varieties, Mills said, they should include ozone resistance in their testing regime.

All of this requires money. Some of it has been secured to tackle air pollution at its source by limiting emissions. But there is also much scope for governments, corporations and equity providers to invest in getting more resistant crops to market. Addressing the “yield gap,” as the paper’s authors dub the phenomenon, is bound to yield appetizing returns. The industry should get started.

Write to the editor at matthieu.f@peimedia.com