Nanjing administrators have promised local residents that they will remove as few plane trees as possible during the construction of a new metro line.

Workers remove plane trees from Taiping North Road in Nanjing, Jiangsu province, to make way for the construction of the city's new metro Line 3. [China Daily]

Last week, an online campaign started calling for protection of 60-year-old plane trees along main roads in Nanjing, capital city of East China's Jiangsu province.

In a few days the campaign on the micro blog platform of sina.com attracted more than 10,000 supporters. Some even proposed a peaceful demonstration on March 19.

Residents were infuriated to see giant plane trees pruned for urban construction projects in Nanjing, but the urban administrators say they are only moving the trees to a new place.

More than 40 plane trees, all about 60 years old, had their crowns cut off, ready for removal, in the Daxinggong area in Nanjing. The trees will give way to a new metro station.

"I was appalled to see dozens of thick plane trees get their crowns chopped off. My heart was bleeding at the sight," a netizen named "Wenhua Yongren" told the local newspaper Jiangnan Times.

Yang Quanqiang, a book editor and resident in Nanjing for more than 15 years, said that the giant plane trees aged 50 years or more lining main streets make a particularly impressive sight in the city, but it's a pity that their numbers have declined over the past decade.

"The city administration owed people a convincing explanation for this," Yang said. "Have they considered the opinions of the residents? Do they have any respect for the history and culture of the city in making their urban development plans?"

On March 14, the city authorities formally responded to these questions and explained why the trees in Daxinggong had to be removed.

"Relevant institutions did several inspections of the area, optimizing the construction plan, but there is still irreconcilable conflict between the subway project and protection of these trees," read the city authorities response, as published on the local Yangtze Evening News.

The subway construction team did change the building plan, decreasing the width of passageways and the number of subway station exits to affect as few trees as possible. According to the Yangtze Evening News report, the smaller passageways to the exits will cause problems when large crowds of people pass through.

The previous subway project designed 13 stations for Line 3. More than 600 trees have already been removed, including not only plane trees but also other species.

The subway construction will have to deal with an even greater challenge of removing some old dawn redwood trees. Unlike plane trees, which are easy to move, dawn redwood trees struggle to survive after being moved and replanted.

"We'd love to remove as few trees as possible in the construction of new buildings or public facilities such as the metro," Xu Shaolin, a spokesman with the city's urban administration bureau told China Daily.

"When we have no other choice, we remove the trees carefully, according to scientific standards: tree crowns are trimmed to stop loss of water, and a big lump of earth is dug with the root to ensure the tree's survival in a new location.

"When the construction projects are finished, it's often impossible to bring the trees back to their old home, because of underground plumbing or the cable system," Xu said.

"Younger trees of the same species are often planted along the main streets, which grow faster and absorb exhaust better than older trees."

Trees removed from the downtown area are often replanted in the suburbs or big squares where the soil allows the trees to survive.

But a few years ago, when plane trees were removed, almost 50 percent of them died. That's why citizens were unwilling to trust the city administration and demanded more supervision of its work.

"Trees decline after a certain age," Xu said. "Every summer we have a few 100-year-old plane trees falling in storms and typhoons. Some casualties are unavoidable."