Serving as a barrier between farmers and nomads in ancient China, the Great Wall was once a site of conflict between the farming Han people to its south and the nomads to the north.

The frequent skirmishes led to a deteriorating ecological environment in the areas adjacent to the walls for thousands of years.

In Shanxi, authorities of counties and cities along the Great Wall have made great efforts to repair the ecological system, exploring a path of green growth and making the areas along the walls more attractive to tourists.

At the Guangwu section of the Great Wall in Shanyin county, the deteriorating environment featuring gradual desertification, frequent sandstorms and severe soil erosion used to be a big threat to the lives of locals and the Great Wall itself.

Authorities in the county began a campaign to improve the environment in 2007 that aimed to curb desertification and prevent sandstorms.

Trees and grasses have been planted along the Great Wall over the past decades. As a result, more than 3,000 hectares of deserts along the wall are now covered in vegetation, according to local officials.

"To further improve the environment, we have planted 5,400 hectares of trees in Shanyin in recent years, expanding the county's forest coverage to nearly 15,000 hectares," said Lan Yechun, deputy chief at the county's forestry and grassland bureau.

Lan said another 400 hectares of forests were added to Shanyin during the first five months of this year.

"As the mountains become greener, the water becomes clean and the sky becomes blue, the sightseeing areas along the Great Wall have attracted more visitors in recent years, bringing more revenue to local residents," the official said.

When reflecting on the 13-year greening campaign, Lan said the achievement was the result of painstaking efforts, especially on steep and craggy mountains and slopes.

"Our forestry workers carried soil onto the slopes of the mountains and hills, where the soil had been washed away after centuries of water erosion," the official said. "Tree-planting tools, saplings and water were also transported by hand."

To collect more rainfall, saplings were planted in deep holes. The soil near the trees was covered by polyethylene sheets to prevent evaporation.

In Datong, a city boasting more than 260 kilometers of the Great Wall, breakthroughs were also made in its greening campaign.

According to the forestry and grassland bureau of Datong, the city invested more than 260 million yuan ($36.77 million) in planting 2,900 hectares of trees in 2019.

Guo Qing, an official at the Datong planning and natural resources bureau, said the city's greening campaigns have taken the local topography, climate, soil conditions and ecosystem into consideration.

"We have planted trees, bushes and grasses according to various conditions to ensure the survival rate of the vegetation," the official said.

Wang Jinfei contributed to this story.