Analysis: Scientists look to solve ozone threat to Africa's food
security
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[August 31, 2022]
By Gloria Dickie
ABERGWYNGREGYN, Wales (Reuters) - 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 aging crops before they reach full production potential and
decreasing photosynthesis, the process by which plants turn sunlight
into food.
![](http://archives.lincolndailynews.com/2022/Aug/31/images/ads/current/LPL_small%201.gif)
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 $24.2 billion annually from 2010 to
2012.
In a January paper published in Nature Food, researchers tallied some
$63 billion 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.
![](http://archives.lincolndailynews.com/2022/Aug/31/images/ads/current/charrons_bch_2022.png)
RISING 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.
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![](../images/083122PIX/news_f7.jpg)
Spatial data analyst Katrina Sharps
examines a wheat crop that has been exposed to increased levels of
Ozone inside a solar dome at the UK Centre for Ecology and Hydrology
research site near Bangor, Britain, July 20, 2022. REUTERS/Phil
Noble
![](http://archives.lincolndailynews.com/2022/Aug/31/images/ads/current/humanesociety_sda022411.png)
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.
"A lot of (ozone) symptoms can be confused with mites or fungal
damage," said CABI entomologist Lena Durocher-Granger. "Farmers
might keep applying fertilizer or chemicals thinking it's a disease,
but it's ozone pollution."
Her organization is working with UKCEH to help people identify signs
of ozone stress and recommend fixes, such as watering less on high
ozone days. Watering can leave leaf pores wide open, causing plants
to take in even more ozone.
RESILIENT CROPS
In her Welsh greenhouses, Hayes was exposing crops in one dome to
the lowest amount - 30 parts per billion - similar to the
environment of North Wales. In the dome with the highest ozone
level, plants were receiving more than triple that amount, mimicking
North Africa's polluted conditions.
Hayes and her colleagues have found that certain African staples are
more affected than others.
In a dome filled with a mid-level amount of ozone, North African
wheat plants had quickly turned from green to yellow within just a
few months.
"You get tiny thin grains that don't have all the good bits in them,
a lot of husk on the outside and not as much protein and nutritional
value," Hayes said.
![](http://archives.lincolndailynews.com/2022/Aug/31/images/ads/current/ldn_sda_062409.png)
That fits with research her team published last year on sub-Saharan
plant cultivars, which found that ozone pollution could be lowering
sub-Saharan wheat yields by as much as 13%.
Dry beans could fare worse, with estimated yield losses of up to 21%
in some areas, according to the same study, published in
Environmental Science and Pollution Research.
"Beans are a useful protein source in Africa, and subsistence
farmers grow a lot of it," said Katrina
Sharps, a UKCEH spatial data analyst.
Sub-Saharan millet, however, seemed more ozone tolerant. Yet Africa
produced about half as much millet as wheat in 2020.
"If the soil and growing conditions are suitable," Sharps said,
"subsistence farmers may consider growing more millet."
(Reporting by Gloria Dickie; Editing by Katy Daigle, Marguerita Choy
and Bill Berkrot)
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