According to the UN, over the past decade, the local government has been improving bike-friendly infrastructure, such as lanes and traffic signals created solely for cyclists, and has provided almost 86,000 public bicycles. A smart card allows users to easily access all forms of public transport, from bikes to boats to buses.

"All together there have been 760 million rides; that's almost half the population of China," said Tao Xuejun, general manager of the Hangzhou Public Bicycle Service. "So far, more than 400 cities in China have adopted our project. Our dream is to promote our model across China and all over the world."

As well as leading the Chinese cycling resurgence, Hangzhou is home to an innovative way to encourage more sustainable lifestyles, with an app that is helping to stop desertification, cut air pollution and plant millions of new trees.

The story introduced the "Ant Forest" mini-program, a Hangzhou-based project from Chinese payment app Alipay. It incites users to make small, environmentally friendly decisions in their daily lives, such as cycling rather than driving to work, or recycling clothes.

When users perform any carbon-reducing activities, they are rewarded with "green energy" points. As they accumulate enough virtual points, a real tree is planted.

UN news wrote, according to Ant Financial, more than 100 million trees have been planted, thanks to the low-carbon actions of 500 million individuals, roughly 5 percent of the world's population.

Beijing's fight against haze was particularly praised by the organization.

"The concentration of fine particulates in the air has fallen by a third over the past two decades, beating the target set by the Chinese State Council," it wrote.

"Beijing has achieved impressive air-quality improvements in a short amount of time," said Dechen Tsering, director of UN Environment's Asia Pacific Regional Office. "It is a good example of how a large city in a developing country can balance environmental protection and economic growth," she stressed.

In a message to mark World Environment Day, UN Secretary General Antonio Guterres emphasized the link between worsening levels of air pollution and the climate crisis.

In the video address released on Tuesday, Guterres said that with the environment facing "unprecedented perils", caused by human activity, action to fight climate change is "the battle of our lives" that must be won by taxing pollution, ending fossil fuel subsidies and halting the construction of new coal plants.