The Kunming environmental protection authority in Yunnan province plans to make each visitor to Dianchi Lake's drainage area pay 10 yuan ($1.59) as ecological indemnity fee.

This has invited criticism from people, who say the government is interested only in making money and is blind to local residents, enterprises and their needs. The government's later announcement that visitors will be charged according to the level of population they create has been lost in the hue and cry.

Some people doubt the local government's capability to curb pollution, because even after spending more than 10 billion yuan ($1.57 billion) since 1998 to clean the Dianchi Lake, it has not been able to rid the lake of eutrophication.

Visitors to the lake certainly have the right to know how their 10 yuan will be spent. The local authorities say the fee would be symbolic, because despite the potential of becoming a stable source of funds, the amount would be nothing compared to the money needed to clean the lake.

The lack of proper dissemination of information is the main cause of the controversy. Almost all the people and the media see it as another case of a local government's arbitrary action. But nobody has bothered to find out how the Dianchi Lake became so polluted. Dianchi is by no means a site polluted by tourists; it is a victim of a long conflict between nature and humans.

This lake, the sixth largest freshwater lake in China, is on the eastern border of the Tibetan Plateau. Its size remained around 1,000 sq km till the mid-13th century when people started turning parts of the lake into farmland. Although they didn't use chemical fertilizers till recently, their encroachments destroyed most of the wetlands surrounding the lake, the most important ecological screen for natural lakes.

The lake shrunk two-thirds to 298 sq km in the 1970s. Its water holding capacity today is only 15 percent of what it was 700 years ago. But the population living around it has exploded from 144,000 in 1510 to 4.67 million in 1998, a 33-fold increase.

Research shows its special geology, local climate conditions and the growing population are responsible, not necessarily in that order, for the pollution of the lake. The rivers flowing into it are too small to lower the pollution level of its water. And 700 years of constant upheaval have made the lake lose its self-purification power. That's why the money needed to clean the water will be astronomical. After all, we have to not only repay the historical debts, but also take care of the ongoing polluting process.

Kunming's downtown covers only 5 percent of the drainage area. But it generates more than 50 percent of the wastewater discharged into the lake. More than 40 million tourists visited the city in 2011, nearly 10 times the local population. If people visiting the city for other purposes are counted, the number of footfalls will be much higher. And each visitor only aggravates the ecological burden of the lake.

It's well known that the speed of developing the sewage treatment system cannot catch up with the increase in population.

So the local government should issue a more convincing and detailed plan about the fee it's going to charge. There is no doubt that every citizen is equally responsible for protection of the environment. Now policymakers need to find the proper way to translate this principle into concrete action.

The author is a writer with China Daily. E-mail: liyang@chinadaily.com.cn