Plant scientist Felicity Hayes checks on her crops inside one of eight tiny domed greenhouses set against the Welsh hills. The potted pigeon pea and papaya planted in spring are leafy and green, soon to bear fruit. In a neighbouring greenhouse, those same plants look sickly and stunted. The pigeon pea is an aged yellow with pockmarked leaves; the papaya trees reach only half as tall. The only difference between the two greenhouse atmospheres — ozone pollution. Hayes, who works at the UK Centre for Ecology and Hydrology (UKCEH), is pumping ozone gas at various concentrations into the greenhouses where African staple crops are growing. She is studying how rising ozone pollution might impact crop yields — and food security for subsistence farmers — in the developing world. Ozone, a gas formed when sunlight and heat interact with fossil fuel emissions, can cause substantial losses for farmers, research suggests, by quickly ageing crops before they reach full production potential and decreasing photosynthesis, the process by which plants turn sunlight into food. Ozone stress also reduces plants’ defences against pests. A 2018 study in the journal Global Change Biology estimated global wheat losses from ozone pollution totalled $24. 2bn annually from 2010-2012. In a January paper published in Nature Food, researchers tallied some $63bn in wheat, rice and maize losses annually within the last decade in East Asia. Scientists are particularly worried about Africa, which will see more vehicle traffic and waste burning as the population is set to double by mid-century. That means more ozone pollution, a major challenge for smallholder farmers who make up 60% of the population in sub-Saharan Africa. “There is a serious concern that ozone pollution will affect yields in the long run,” said senior scientist Martin Moyo at the International Crops Research Institute for the Semi-Arid Tropics in Zimbabwe. He called out an “urgent need for more rural studies to determine ozone concentrations” across the continent. Earlier this year, scientists with the UK-based non-profit Centre for Agriculture and Bioscience International (CABI) set up ozone monitoring equipment around cocoa and maize fields in Ghana, Zambia and Kenya. But most African countries do not have reliable or consistent air pollution monitors, according to a 2019 Unicef report. Among those that do, few measure ozone. In the stratosphere, ozone protects the Earth from the sun’s ultraviolet radiation. Closer to the planet’s surface, it can harm plants and animals, including humans. While air quality regulations have helped reduce ozone levels in the United States and Europe, the trend is set to spike in the opposite direction for fast-growing Africa and parts of Asia. Climate change could also speed things along. In areas of Africa with high fossil fuel emissions and frequent burning of forests or grassland, new research suggests hotter temperatures could make the problem worse as they can accelerate chemical reactions that create ozone. While research has found North American wheat is generally less impacted by ozone than European and Asian counterparts, there have been fewer studies on African versions of the same crops that over decades of cultivation have been made more suitable to those environments. Once every two weeks in a Nairobi market, farmers from the countryside bring samples of their ailing crops to a “plant doctor” in hopes of determining what is affecting their yields. – Reuters.