Liu Daye, 53, spent 11 years felling trees in Hainan province's Jianfengling Mountains - home to China's largest old-growth tropical rainforest. Now he spends his time preventing others from doing damage to the same area.

"What I'm doing is making up for what I did in the past," he said.

More than 3,000 plant species and over 4,700 animal species are in the rainforest in the western part of the island province.

For at least 22 days each month, Liu patrols over 100 kilometers of the jungle, searching for poachers and fire hazards, and monitoring the environment.

From 1981 to 1992, Liu worked for a logging company, which had seven forestry farms and nearly 6,000 employees in its heyday.

"The country's construction boom at the time required a lot of quality wood," Liu recalled. "But the way trees were felled was destructive and unsustainable."

Lumberjacks preferred the best and biggest trees, leaving the forest in a bad state, he said.

Liu and his fellow workers put down their axes and saws after rising environmental protection awareness led to the end of logging in the forest in 1993.

In 1998, a conservation campaign was launched to restore the forest. Two years later, some former lumberjacks, including Liu, were hired as rangers. He now earns about 4,000 yuan ($620) a month.

The most dangerous part of the job is dealing with poachers.

In late 2010, two poachers riding through the forest on a motorcycle encountered Liu, who was on duty at the time. Liu wrestled a shotgun from one of the poachers and stuck it into the spokes of the motorcycle's wheel.

"The poachers fled, but at least I ruined their weapon," he said, holding up the twisted barrel of the gun.

The rangers' work also includes raising awareness among villagers about the importance of wildlife protection and encouraging them to assist experts with their field research.

Liu and his colleagues once saved a boa constrictor that had entered a village and was caught by residents. They planned to kill it until Liu told them that it was under State protection.

"It is not an easy job, but I'm so glad to see what we have changed," he said.

Liu's efforts appear to be paying off. According to statistics from the forestry bureau of the Jianfengling Mountains, the rainforest has increased by nearly 4,000 hectares over the past 20 years.