[ABERGWYNGREGYN、ウェールズ、8 月 31 日 ロイター]- Plant scientist Felicity Hayes checks her crops in one of eight small domed greenhouses set against a backdrop of Welsh hills. Potted pigeon peas and papaya planted in spring are lush and ready to bear fruit.
In the greenhouse next door, the same plants look sickly and stunted. Pigeon peas are ripe yellow with pockmarked leaves. Papaya trees only reach half height.
The only difference between the atmospheres of the two greenhouses is ozone pollution.
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Working at the UK Center for Ecology and Hydrology (UKCEH), Hayes pumps varying concentrations of ozone gas into greenhouses where staple African crops are grown. She studies how increasing ozone pollution affects crop yields in developing countries and food security for subsistence farmers.
Ozone, a gas produced when sunlight and heat interact with fossil fuel emissions, rapidly ages crops before they reach their full productive capacity, a process by which plants convert sunlight into food. Research suggests that reducing some photosynthesis can result in large losses for farmers.
Ozone stress also reduces plant defenses against pests.
A 2018 study published in the journal Global Change Biology estimated that from 2010 to 2012, ozone pollution caused global wheat losses of $24.2 billion annually.
In a January paper published in Nature Food, researchers tallied that wheat, rice and corn in East Asia lost about $63 billion annually over the past decade.read more
Scientists are particularly concerned about Africa, where the population is expected to double by the middle of the 20th century, increasing vehicle traffic and incinerating waste.
This means increased 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 term,” said Martin Moyo, senior scientist at the International Crops Research Institute for the Semi-Arid Tropics in Zimbabwe.
He called for “more rural surveys to determine ozone concentrations are urgently needed” across the continent.
Earlier this year, scientists at the UK-based non-profit International Center for Agricultural and Biological Sciences (CABI) installed ozone monitors around cocoa and corn fields in Ghana, Zambia and Kenya.
However, according to a 2019 UNICEF report, most African countries lack reliable or consistent air pollution monitors. Very few measure ozone.
In the stratosphere, ozone protects the earth from the sun’s ultraviolet rays. Getting close to the earth’s surface can harm plants and animals, including humans.
Air quality regulations have helped bring down ozone levels in the United States and Europe, but the trend is set to soar in the opposite direction in rapidly growing parts of Africa and Asia.
Climate change could also accelerate things.
In regions of Africa with high fossil fuel emissions and frequent burning of forests and grasslands, higher temperatures could exacerbate the problem as the chemical reactions that produce ozone can be accelerated. New research suggests that
Studies have found that North American wheat is generally less susceptible to ozone than European and Asian wheat, but fewer studies have been done on African versions of the same crop, indicating that decades of cultivation have affected those environments. is more suitable for
Every two weeks at a market in Nairobi, rural farmers bring diseased crop samples to a ‘plant doctor’ to find out what is affecting yields.
“Many of the symptoms[from ozone]can be confused with mite or fungal damage,” says CABI entomologist Lena Durocher-Granger. “Farmers may continue to use fertilizers and chemicals thinking they are sick, but that is ozone pollution.”
Her organization works with UKCEH to help people identify signs of ozone stress and recommend measures such as watering less on ozone-rich days. Watering leaves pores in the leaves open, which can allow the plant to take in even more ozone.
In her greenhouse in Wales, Hayes exposed the crops in one dome to a minimal dose (30 ppb) similar to the North Wales environment. At the dome, where ozone levels are highest, plants receive more than three times that amount, mimicking the polluted conditions of North Africa.
Hayes and her colleagues found that certain African staples were more affected than others.
In a dome filled with moderate amounts of ozone, North African wheat rapidly changed from green to yellow in just a few months.
“You get small, thin grains that don’t have all the good bits, with a lot of shell on the outside and not as much protein and nutrition,” says Hayes.
This is consistent with a study her team published last year on sub-Saharan plant varieties, which found that ozone pollution can reduce sub-Saharan wheat yields by as much as 13%. did.
The same study, published in Environmental Science and Pollution Research, found that dried beans could be even worse, reducing estimated yields by up to 21% in some areas.
“Beans are a useful source of protein in Africa and subsistence farmers grow beans in large quantities,” Katrina said.
UKCEH Spatial Data Analyst Sharps said:
However, sub-Saharan millet appeared to be more ozone-tolerant. However, Africa produced about half as much millet as wheat in 2020.
“If the soil and growing conditions are right, subsistence farmers may consider growing more millet,” Sharpes said.
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Reporting by Gloria Dickey.Edited by Katie Daigle, Margherita Choi and Bill Barclot
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