Analysis – Scientists search for a solution to the ozone threat to Africa’s food security

In a nearby greenhouse, those same plants look sick and sloppy. aged pigeon pea yellow with patterned leaves; Papaya trees grow to only half that height.

The only difference between the two atmospheres – ozone pollution.

Hayes, who works at the UK Center for Environment and Hydrology (UKCEH), pumps ozone in varying concentrations into the greenhouses where essential African crops grow. She studies how increasing ozone pollution may affect crop yields – and the food security of subsistence farmers – in developing countries.

Research shows that ozone, a gas produced when sunlight and heat interact with fossil fuel emissions, can take a huge toll on farmers, because crops age quickly before they reach their full productive potential and by slowing down photosynthesis, the process in which plants transform Sunlight into food, it is reduced.

Ozone stress also reduces the plants’ defense system against pests.

A 2018 study https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.14157 in the journal Global Change Biology estimated global wheat losses from ozone pollution at $24.2 billion annually from 2010 to 2012.

In a research paper published in January, https://www.nature.com/articles/s43016-021-00422-6 published in Nature Food, researchers counted about $63 billion in losses to wheat, rice, and corn annually in the past 10 years. in East Asia.

Scientists are particularly interested in Africa, where car traffic and waste burning will increase as the population will double by mid-century.

This means more ozone pollution, and it is a major challenge for smallholder farmers, who account for 60% of the population in southern Africa from the Sahara.

“There is great concern that long-term ozone pollution will affect crops,” said chief scientist Martin Moyo of the International Crop Research Institute for the Semi-Arid Tropics in Zimbabwe.

He called for “the urgent need for more studies at the national level to determine ozone concentrations” across the continent.

Earlier this year, scientists from the UK-based non-profit Center for Agriculture and Biosciences International (CABI) set up ozone monitoring equipment around cocoa and maize fields in Ghana, Zambia and Kenya.

But most African countries lack reliable or consistent air pollution monitoring devices, according to a 2019 UNICEF report https://www.unicef.org/media/55081/file/Silent_suffocation_in_africa_air_pollution_2019.pdf. Of the countries that have it, few measure ozone.

Rising ozone

In the stratosphere, ozone protects the Earth from the sun’s ultraviolet rays. Close to the Earth’s surface, it can harm plants and animals, including humans.

While air quality regulations have helped reduce ozone concentrations in the United States and Europe, the trend in fast-growing Africa and parts of Asia will be in reverse.

Climate change could also speed things up.

According to new research, in regions of Africa with high fossil fuel emissions and frequent burning of forests or grasslands, higher temperatures can exacerbate the problem, as they can speed up the chemical reactions that create ozone.

Research has shown that https://www.sciencedirect.com/science/article/abs/pii/S0048969719305704 North American wheat is generally less affected by ozone than European and Asian wheat, but less research has been done on African wheat. The same crops, which have become better suited to that environment over decades of farming.

At a market in Nairobi, once every two weeks, rural farmers bring samples of their faltering crops to a “botanist” in hopes of determining what is affecting their crops.

“Many (ozone) symptoms can be confused with mites or a fungal infestation,” said CABI entomologist Lena Dorocher Granger. “Farmers may continue to use fertilizers or chemicals assuming it’s a disease, but it pollutes the ozone layer.”

Her organization works with UKCEH to help people recognize the signs of ozone stress and recommend solutions such as reducing watering on days when the ozone concentration is high. Watering can leave leaf pores wide open, causing plants to absorb more ozone.

resistant crops

In her Welsh greenhouse, Hayes exposed crops in one dome to the lowest amount – 30 parts per billion – compared to the environment in North Wales. In the dome with the highest ozone content, plants received more than three times that, mimicking the polluted conditions in North Africa.

Hayes and her colleagues found that some African commodities are affected more than others.

In a dome filled with an average amount of ozone, wheat plants in North Africa quickly turned from green to yellow within months.

“You get small, thin pellets that don’t have all the good parts in them, lots of flakes on the outside and not a lot of protein and nutritional value,” Hayes said.

This fits with research her team published last year on sub-Saharan plant varieties, which showed at https://pubmed.ncbi.nlm.nih.gov/34191262/ that ozone pollution affects wheat yields in sub-Saharan Africa by potentially declining. As much as 13%.

Dry beans could be even worse, with yield losses estimated as high as 21% in some areas, according to the same study published in Ecology and Pollution Research.

“Beans are a useful source of protein in Africa, and many of them are grown by subsistence farmers,” Katrina said.

Sharps, a spatial data analyst from UKCEH.

However, sub-Saharan millet appeared to be more ozone resistant https://www.sciencedirect.com/science/article/pii/S2468227620302209. However, in 2020, Africa produced about half as much millet as wheat.

“If the soil and planting conditions are appropriate, subsistence farmers might consider planting more millet,” Sharps said.

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