A report on the sustainable development of Chinese cities has been released in Beijing.

The report was issued by the United Nations Development Program after evaluating 35 cities.

It suggests that the overall trend of these cities' sustainable development is optimistic.

Alain Noudehou is the UNDP resident representative in China.

"Some cities have made tremendous progress if I name, for example, the cities of Wuhan and Changsha. They have made very good progress in balancing achievements of human developing, but at the same time minimizing also the impact they have on the ecology and environment. And those cities, they have something that we should all learn from"

Wuhan and Changsha have also been awarded the "2015 sustainable development" prize.

The capital, Beijing, and six other cities, are believed to be able to achieve higher levels in sustainable development while minimizing environmental damage.

The report was released at the 2015 International Forum on Sustainable Cities, held in Beijing.

Zhu Dajian, a professor of Tongji University, thinks the government should maintain cities' sustainable development in four aspects.

"By addition we mean to increase urban populations and the quality of human development. Subtraction is to reduce our consumption of energy and the environment. Multiplication is to change the previous land-related revenue and capital into capital input through multiple channels. Division is to break down and streamline government functions. In this way, the whole society can be involved in the cities' development."

Currently, the number of urban residents accounts for 55 percent of China's population.

60 percent of the population will be living in cities by 2020.