Need more room for construction? Get rid of the mountains.
That’s what is happening in parts of China, including the region around the city of Lanzhou in the central part of the country, where the government hopes to add 250 square kilometers of buildable ground by removing the tops of about 700 mountains and filling in valleys with the material. Similar efforts are under way near Yan’an, where available land will be nearly doubled, and several other cities. The goal is to create space for people from rural areas to move into the cities.
Three environmental scientists from Chang’an University in Xi'an, China, published a paper in Nature last week criticizing the decade-old practice. They say the environmental impacts of reshaping the land on such a large scale are not well understood, citing the deforestation, habitat destruction, dust pollution, and increased erosion and sedimentataion it causes.
In addition, they say, there is too little experience in building dense urban structures on the type of soils that are being removed from the mountains and used as infill. “Yan’an, for example, is the largest project ever attempted on loess, thick million-year-old deposits of wind-blown silt. Such soft soils can subside when wet, causing structural collapse,” they write.
If the process continues, they recommend increased research and collaboration among many organizations, both within China and internationally: universities, research institutes, private companies, construction teams, and governments. They are calling for experts not only in hydrogeology and engineering geology but also in soil-water research to look at the long-term effects of the practice.
You can see the Nature article here and a brief summary from The Guardian here.