“In the last 50 years there has been a 16-fold increase in ozone pollution” in the Beijing area, said Hanqin Tian of Auburn University in Alabama, who studies the effects of China’s pollution and climate change on plants. He said the soup of pollutants, including harmful sulfur and nitrogen compounds “is definitely expanding into new areas; into the countryside.”
Ozone is particularly harmful to plants because it damages the pores on leaves, called stomata, which plants use to regulate how much water transpires from the leaves. That, in turn, affects how much water a plant must take up through its roots. Changes in water uptake by plants have been documented in other parts of the world, including the United States, as having major impacts on regional groundwater and surface water supplies.
“So you could affect the water cycle,” said Hanqin Tian. That’s probably not such a good thing in a changing climate and in northern China, where droughts have become a chronic problem, he explained.
The ozone pollution in this case is not the naturally occurring ozone layer up in the stratosphere, which protects Earth’s surface from ultraviolet radiation. Rather, it’s an entirely man-made byproduct of internal combustion engines in cars.
This is particularly alarming as China relies on rural crops to feed its skyrocketing population. Those same crops took a hit due to a cold snap earlier this month, which saw temperatures drop to the lowest national average in 28 years, -3.8C (25F).
Studies also show that plants living in highly-polluted areas like Beijing are more likely to resist the leaf-damaging effects of smog than those in the countryside. But don’t get any ideas about starting urban vegetable gardens on Beijing rooftops, unless you want your zucchini patch to turn into Swamp Thing.
Currently, of the world’s 10 most polluted cities, 7 are in China.