Urban planning divides urban areas into three categories: areas appropriate for construction, restricted construction areas and areas forbidden to construction. "Those restricted and forbidden areas should be reserved for ecological construction projects, but today's city planners often neglect using scientific planning and sell the areas to business people for commercial purposes," Zhou said.

Hangzhou is surrounded by mountains on three sides. In summer, it relies on the wind from the Qiantang River in the southeast to help the urban areas cool down. However, the city's planners have started changing the development strategy for the city and decided to develop the area surrounding the river into a business zone.

A number of skyscrapers have already been erected along the both sides of the Qiantang River. "The consequences of this badly thought out plan was presented to planners this past summer," Zhou said, warning that more extremely hot summers will be experienced in the coming years due to Hangzhou's unbalanced planning.

According to local meteorological authorities, Hangzhou was hit by 40.6 degrees Celsius on August 6, the highest temperature there since 1951.

Another factor adding to the severity of the UHI effect is the occupation of waterways.

"One of the main activities in the previous 30 years of China's construction has been to fill rivers," said Liu Bo, Director of the Publicity and Education Center at the Sanitation Bureau of Changde City, central China's Hunan Province.

Today, the traditional water systems and wetlands have been replaced by watertight road surfaces in many cities. "In some cities, the urban hardness ratio has reached over 80 percent, while the natural infiltration rate for rain has decreased below 20 percent," Liu said.

Liu has long been calling for reducing the hardness of surfaces in cities. He said, "A modern city should be a spongy city, combining its urban sewage system with the city's natural water system, including rivers, lakes and underground water sources tightly together."

Xuan Chunyi, an engineer with the Beijing Climate Center, has studied urban water systems for many years. "Whether a city has is decentralized or centralized water systems, the increase in a city's total water surfaces reduces the severity of the UHI effect," he said.

"The UHI effect in Chengdu, capital of Sichuan Province, had increased year on year before 2003. With green areas and wetlands expanding in the city in recent years, the intensity of the effect has declined," said Dan Shangming, a retired senior engineer with the Sichuan Provincial Meteorological Bureau.

Green remedies

"To alleviate the UHI effect, it is imperative to increase the areas allocated to bodies of water and green foliage," said Li Yanming, a senior engineer at the Beijing Research Institute of Garden.

Research shows that when a city's foliage coverage surpasses 40 percent, the urban heat effect will be lowered notably. According to satellite remote sensing data, the building of a central green area has helped erase the original four heat islands in the Lujiazui area in Shanghai.

"There are too few green areas in Chinese cities," Zhou said. According to him, an indispensable factor for an "advanced" city in foreign countries is that its per-capita green coverage should reach 30 square meters, but in China, a nationally designated "garden city" only requires about 10 square meters for each person.

In recent years, city planners have started putting importance on the placement and preservation of green areas, but Zhou said that a new mistaken idea has also emerged alongside this—the "green patch plus flower" planning undertaken in most Chinese cities.

"We put too much emphasis on landscape. In reality, green work is a multi-level project, requiring proportionally putting trees, shrubs, flowers and ground cover plants together," Zhou noted.

Yu believes that for every city, the ecological meaning should be more important than the landscape consideration of its green work. "It's only a great quantity of trees that can make real relief to the UHI effect," Yu said.

He emphasized that one of the major projects undertaken in city green work has to provide areas of shade provided by trees between buildings, and this requires particularly tall trees in large numbers.

However, in order to make room for infrastructure construction, many local governments have chosen to move or even cut down existing trees.

In 2011, the authorities of Nanjing, capital of Jiangsu, decided to move some of the city's French plane trees, which were planted between 1912 and 1949, to make way for the construction of a subway line. This decision incited protests from local residents. Eventually the plan was called off due to public pressure.

Without destroying trees or even planting more, the outlook for China's green system construction is still not optimistic. "In green area planning, there are upper and lower limits. Our planners always choose the lower limits," Zhou said.

Take the green work along the Qiantang River in Zhejiang for example. The 1,000-meter-wide river requires a 100- to 150-meter-wide green corridor on each side, but only a 30-meter-wide belt is built along each side of the river today. "The tiny green belts will go a very little way in relieving the UHI effect in the area," Zhou said.

Li Shuhua, a professor at the School of Architecture of Beijing-based Tsinghua University, has led research into the effects of Beijing's river lands. The research concluded that "only those green belts surpassing a width of 45 meters can reliably absorb the surrounding heat and reduce the strength of the surrounding UHI effect."

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