"By comparing the results of the previous year, we can figure out whether an area of forest has increased or decreased. If some parts shrink, we will check if these changes were formally approved or contact the police if further action is needed," he says.

"Before the technology was introduced in 2014, we mainly acted on complaints and reports from the public, before sending staff to investigate them by using maps to identify any reduction in tree cover, which was time-consuming and arduous."

The province has introduced extensive measures and legislation to protect forests, from banning the felling or damaging of trees and the illegal picking of wild plants, to prohibiting picnics and other activities that could cause fires, and outlawing the removal of rocks, sands or soils that may damage the vegetation, according to the forestry bureau.

Basic guidelines for the conservation and expansion of forestry include returning farmland to forestry, planting sheltered forests along the Yangtze and Pearl rivers, and controlling desertification, says Zhang.

A study by the journal Natural Sustainability in February found that since 2000 the Earth's green leaf area has increased by 5 percent - an area equivalent to the entire Amazon rainforest.

China contributed to 25 percent of the planet's increase in forest cover, despite having only 6.6 percent of the world's vegetation, the report says.

Li Hanyi contributed to this story.