Cai Yijun spent the end of March sneezing. With Shanghai and much of eastern China blanketed by dust and sand, the 23-year-old marketing consultant’s chronic rhinitis, or nose inflammation, took a turn for the worse.

The air quality index for the region topped out at 500, its worst possible reading, due to high concentrations of particles up to 10 micrometers in size, called PM10. As these can be harmful to health, the Shanghai government told people to stay indoors or wear masks when going outside.

Shanghai’s dusty days were connected to the sandstorms that affected around 240 million people across large swaths of northern China last month, Wu Rui, chief service officer at the Shanghai Meteorological Bureau, told Sixth Tone.

The dust whipped up during a sandstorm can remain suspended in the air for days, causing skin and eye irritations, as well as penetrating people’s upper respiratory tract and even lungs. Sandstorms have been linked to upticks in respiratory disorders such as asthma and bronchitis, as well as increased mortality.

More than a quarter of China is desert, and desertification of adjacent areas is a major issue. Sandstorms are common, especially during spring. But the current season stands out for the frequency and strength of the storms, a worrying sign that a warmer future will be dustier, scientists told Sixth Tone.

What caused the recent sandstorms?

Ma Quanlin, deputy director of the Gansu Desert Control Research Institute in China’s northwest, told Sixth Tone that while the sandstorms mainly originated from Mongolia, China’s neighbor to the north, part of the airborne dust also came from the Taklamakan Desert, one of China’s four major dust source regions.

A satellite image captured on March 15 shows how the two regions appear to contribute to a sandstorm that, in Mongolia, killed six people and more than 2,000 heads of livestock. In another satellite image from March 27, a sandy cloud can be seen floating south from Mongolia. Like China, the country is dealing with desertification.

Climate change due to human activity likely increased the magnitude of recent sandstorms, Wu Liguang, a meteorologist at Fudan University in Shanghai, told Sixth Tone. Mongolia has warmed at three times the global average rate over the past 80 years, Wu said. Making similar observations, researchers warned in a paper published in Science in November that an abrupt shift to warmer and drier weather over inner East Asia is potentially irreversible.

How effective is China’s afforestation campaign?

To combat desertification, governments in China’s drier areas have resorted to mass tree-planting to stabilize sand dunes. As part of the Three-North Shelterbelt Forest Program, one of the largest such initiatives, trees were planted on 30 million hectares of dusty regions by late 2020.

But this Spring’s sandstorms raised doubts online about the effectiveness of such projects. Ma, of the Gansu Desert Control Research Institute, explained that such “shelterbelts” are only effective at keeping local sand and dust at bay. “The transitory sandstorms mostly come with a thousand-meter-high dust wall. The height of a shelterbelt system is limited,” he said.

What does the future hold?

Sandstorms are a natural weather event, Ma said, and so they will definitely occur again when the right conditions are met. According to Fudan University’s Wu, the issue will likely get bigger. “According to current research, sandstorms will probably become more severe in the future,” he said.

Climate change is likely a catalyst for stronger storm seasons, as it’s drying out larger areas and affects the severity of heat waves. “If the baseline conditions hadn’t deteriorated, then sandstorms would not have become this intense even with the right weather conditions,” Wu said.

Many future sandstorms traveling across China will likely originate, at least in part, in Mongolia, Ma said. There, overgrazing and over-mining are putting pressure on the country’s fragile ecosystems, resulting in grassland turning into desert. Ma’s institute is holding training sessions for Mongolian officials about mass planting of saxauls — small, tree-like shrubs that can settle sandy areas.

China has made the same mistakes Mongolia is making now, Ma said, including overusing groundwater. If the country follows such a development model, he warned, “the resulting issues will definitely be the same as those we’ve faced before.”

Addition reporting: Zhang Shiyu; editor: Kevin Schoenmakers.

(Header image: Workers look out at buildings silhouetted against dusty skies in Qingdao, Shandong province, March 29, 2021. He Yi/People Visual)