In early spring, Xiao Meng and his colleagues at the Huangshi National Mine Park in Central China's Hubei province were busy planting locust trees alongside local residents at the former mine site.

"In the past, it was a barren waste rock field. Now, the saplings I planted have grown into forests," the 58-year-old former miner said.

Xiao, now a security guard at the park in the city of Huangshi, has been planting trees on the site for nearly 40 years and has witnessed the environmental improvements taking place in the park.

The Huangshi National Mine Park was built on the site of the century-old Daye iron mine. Due to years of exploitation, three local mines had turned into three huge pits with an average drop height of over 400 meters, and over 300 million tonnes of waste rock had been dumped at the mine site.

"When the wind blew, the dust floated in the air, and when it rained, the slurry flowed," Xiao said, noting that the conditions not only harmed the health of the miners, but landslides and soil erosion also brought inconvenience and dangers to nearby residents.

Yan Hongyong, who is in charge of the management office of Huangshi National Mine Park, said that at that time, workers originally planned to plant vegetation to treat the problems caused by the waste rock field. However, the waste rock was hard and had poor water retention, so normal plants could not survive.

"After years of efforts, local technicians found that locust trees were highly drought-resistant and nitrogen-fixing with their rich roots, and they were able to grow on these rocks," Yan said. Tens of thousands of people have since come to plant locust trees on the field every year, including the workers at the mine and local residents, Yan added.

"However, due to the harsh environmental conditions, not every locust tree planted can survive," said Wu Fangqi, a 73-year-old retiree from the Daye mine site.

To improve the survival rate of the trees, people dug large holes in the waste rock piles, filled the pit with slag and fertilizer, and watered the locust saplings they planted every few days, Wu said.

More than 1 million locust trees have been planted on the waste-rock area over the past four decades, forming an ecological forest spanning some 3.6 million square meters.

Now, the mine site has been turned into a tourist attraction.

"The Huangshi National Mine Park attracts more than 300,000 visitors every year," Yan said."When the locust trees blossom, the park is filled with tourists."