As a citizen of Hong Kong, I thought about using my column on the 10th anniversary of Hong Kong's return to Chinese sovereignty to praise the Special Administrative Region's rule of law and freedom and to praise the notion of "one country, two systems".

However, precisely because the two systems ultimately belong to the one country, and because Hong Kong cannot sustain its well-being without the entire Chinese mainland developing in a healthier way, I finally decided to devote this column to an event that is not as highlighted as Hong Kong's anniversary.

That was Premier Wen Jiabao's weekend inspection trip to Taihu Lake, site of an environmental crisis in mid-May. A sudden overgrowth of blue algae polluted the daily water supply for millions of lakeside people.

The accumulation of chemical contamination from industrial discharge from lakeside cities, mainly Wuxi and Changzhou, triggered the blue algae's growth over huge areas of the lake's surface. The algae destroyed the water's oxygen content, killing all other lake life and creating an unbearable stench.

Hong Kong is far from Taihu Lake. The lake belongs to the Yangtze River system while Hong Kong is on the South China Sea. But the quality of the mainland water system matters a great deal to Hong Kong since Hong Kong gets most of its drinking water from the Pearl River.

Similar to Taihu Lake, plenty of newly industrialized towns and cities are developing along the Pearl River and its tributaries. Presumably they will soon be joined by more cities with more factories and more sewage discharge.

Moreover, no matter where Hong Kong or any city or individual gets water for today or tomorrow - from the bottles in supermarkets or from hugely expensive desalination projects - we all belong to the same planet.

Countries that are developing faster than others also bear larger environmental responsibilities. If China does not quickly digest the lessons that are already popping up one after another to disturb its development, it may set a disappointing example.

But if it demonstrates - as Premier Wen pledged on his Taihu trip - both strong will and effective governance in the control of pollution and all other environmental hazards, China will be doing a great favor to the world.

The cruel fact is that, as the premier may have learned from his lakeside trip, keeping the environment clean may be more complicated and expensive than many people are prepared for.

The lakeside cities contribute 45 percent of the gross domestic product (GDP) to Jiangsu Province, one of the most powerful provincial economies in China. So the local officials might have thought the factories they built were too important to interfere with, whether or not they treated their waste water.

But that very mindset, which Chinese critics call the GDP fetish, not only wasted well over 10 billion yuan ($1.3 billion) of government funds in the past on blue algae control. It has also given rise to much greater costs to correct the current problem.

Some scientists estimate it would cost at least 200 billion yuan ($26.3 billion) to restore Taihu's environmental quality to the level of just 30 to 40 years ago.

Fighting pollution now looks like a mammoth challenge for us.

E-mail: younuo@chinadaily.com.cn