“I can finally see the light in the protection of Dianchi Lake,” Zhang said.

Covering 330 sq km (127 square miles), the freshwater lake is the biggest of its kind in southwest China and one of the most popular scenic spots in Kunming, the capital of Yunnan province.

The bond between Zhang and the lake dates back decades. Born in 1948, Zhang’s father died when he was five and his mother later left him and his two younger brothers to fend for themselves. When his siblings died, Zhang, then aged seven, went to live on the mountain on the west bank of the lake by himself, though he maintained contact with villagers who occasionally gave him food, clothes and other necessities.

“Spring and summer were the best seasons,” he said. “There were all kinds of wild fruit on the mountain – strawberries, bayberries, apricots.”

But there were also wolves, bears and leopards and he would hide in the trees when he heard the breath of leopards. Squirrels were his best friends, he said.

“They won’t harm me and they lived happily,” Zhang said. “I just followed them to find pine nuts and saved them for food through the winter.”

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When he was 14, he had a yearning for knowledge, so he left the mountain and returned to live in Fushan village near Dianchi Lake. His childhood experiences taught him about nature and laid the foundation for his conservation work in his later life – his unique experience made him stand out among China’s environmentalists.

“Dianchi Lake and Changyao Mountain are like my parents. They raised me,” he said.

Zhang’s fight against pollution began in the 1980s when China began its economic reforms. Investors were drawn to the mountains around Dianchi Lake because of the abundant mineral resources and spruce trees. Mines and workshops sprang up everywhere.

Zhang said the situation was at its most severe in the 1990s when quarrying and illegal logging almost ran out of control. Almost every week, he reported his findings to the environmental protection bureau.

He said he had probably made 30,000 complaints over the years, which had led to more than 160 polluting factories and over 40 quarry mines being closed down. In 2009, he won an “Inspiring China” award, which he received at an event that was broadcast on national television.

Despite the accolades, Zhang and his family were often harassed by miners and the owners of polluting factories. In 2002, he was hit by a truck while taking photographs at a quarry which cost him the sight in his right eye and a broken wrist.

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Zhang has married twice but both his wives and his three daughters left him. One of his friends who fought with him over a polluting factory was beaten to death in the 1990s.

But Zhang said he was not afraid.

“I’m not afraid of death but I feel sorry for my family and friends,” Zhang said. “I feel miserable whenever I think about them.”

After years of investment and conservation, water quality in Dianchi Lake has begun to show signs of recovery. According to state media reports, authorities have spent more than 50 billion yuan (US$7.7 billion) cleaning it up.

Now aged 73, Zhang still cares about the lake. Every week, he takes a taxi ride around it to check for polluters and he continues to report malpractices and environmental violations.

“After my death, I want to become an eagle so I can hover over Dianchi Lake, or become a spruce tree planted on the west side of the lake so I can continue to watch over it,” he said.