Editor's note: As protection of the planet's flora, fauna and resources becomes increasingly important, China Daily is publishing a series of stories to illustrate the country's commitment to safeguarding the natural world.

On a recent winter morning, Chen Botao launched his drone over a forest farm in Xichuan county of Nanyang, Henan province. On his drone controller's display screen, a live feed showed hundreds of trees stretching toward a reservoir's edge. It took the drone 30 minutes to complete a patrol task around the forest.

His father, Chen Renfan, a veteran forest ranger, remembered when checking the same forest meant leaving before dawn, making their way through the woods, climbing the steep slopes, and not returning until the light failed. A patrol that now takes his son half an hour once took him an entire day.

For over four decades, the older Chen was part of a team that did the unthinkable: they turned a dust bowl into a forest, one bucket of soil at a time.

Today, the Taizi Mountain Forest Farm stands as a barrier to the Danjiangkou Reservoir, which stretches across Henan and Hubei provinces and is a source of China's South-to-North Water Diversion Project, providing water to northern regions more than 1,000 kilometers away, including Beijing and Tianjin.

Before the water begins its journey to North China, it passes through the farm. What happens on this 22-square-kilometer patch of forest land affects the drinking water of millions.

More than 40 years ago, this was a wasteland.