The Danger of Moving Mountains for China's Urban ExpansionChristina Larson
To create more flat land for the fast-growing cities in western China, local planners are increasingly turning to the drastic measure of bulldozing mountaintops and filling in valleys with dump trucks full of dirt.
The impact of such massive earthmoving projects will have on soil conditions, erosion, groundwater, and other environmental factors remains largely unknown. Nor is it clear whether the filled-in land will provide adequate structural support for tall buildings; construction on unstable foundation has led to new high-rises tumbling elsewhere in China.
Three scientists from the School of Environmental Science and Engineering at Chang’an University in Xi’an last week published a forceful commentary in the journal Nature warning that “earthmoving on this scale without scientific support is folly.” As an example, they highlighted the city of Yan’an, in China’s central Shaanxi province, where planners aim to “double the city’s current area by creating 78.5 square kilometers of flat ground.” While the potential revenue from land sales is high, the scientists argue the risks are higher:
“Yan’an is the largest [earthmoving] project ever attempted on loess—thick, million-year-old deposits of windblown silt. Such soft soils can subside when wet, causing structural collapse.”
Unfortunately, scientists have been largely sidelined from the planning process. “In Yan’an, the research started three months after excavations began,” the letter in Nature reads. “Lab tests that could have established the exact moisture content needed to harden loess foundations were unavailable to guide the project. Preliminary results are now available, but for only a few soils.”
Mountaintop removal projects elsewhere in China are wreaking havoc on the environment. Near the central city of Shiyan, the scientists note, “the changing of hills to plains has caused landslides and flooding, and altered watercourses.” Near the western city of Lanzhou, where mammoth earthmoving projects are under way, researchers have estimated soil erosion will increase by 10 percent, and the concentration of dust particles in the air will increase by almost 50 percent.
As the scientists conclude, “Land creation by cutting off hilltops and moving massive quantities of dirt is like performing major surgery on Earth’s crust.” Moreover, “it has never been carried out on this scale … [and] there are no guidelines.”