One day in 2012, Zhu had dinner at a friend's home after work. The main meal was stewed mutton. Zhu asked his friend about the recipe and his friend showed Zhu a plant-it was the mysterious flora he had seen a year ago. Zhu learned that the plant was a saxaul tree.

Saxaul trees, or Haloxylon ammodendron, an ultraxerophytic small tree of the Chenopodiaceae family, are an excellent tree species for sand fixation and afforestation in desert areas. It's commonly seen, though easily ignored. It is widely distributed in Chinese desert regions, such as Inner Mongolia, the Ningxia Hui autonomous region and Gansu province.

Known as a desert guardian, a fully grown saxaul tree can hold together a 10-square-meter patch of desert land, according to Zhu.

"I didn't expect that the small plant would change my life," says Zhu, 35, who quit his job at the design institute in 2014 and joined a nonprofit organization, the Society of Entrepreneurs and Ecology Conservation, or SEE, in the same year, concentrating on tackling desertification.