Children walk next to a sand dune during a voluntary tree-planting event organised by their school and the Wang family, on the edge of the Gobi desert, on the outskirts of Wuwei, Gansu province, China, April 16, 2021. Tree-planting has been at the heart of China's environmental efforts for decades as the country seeks to turn barren deserts and marshes near its borders into farmland. Experts say China's reforestation work has become more sophisticated over the years with the government benefiting from decades of experience and able to mobilise thousands of volunteers to plant trees, emulating frontline pioneers like the Wangs. REUTERS/Carlos Garcia Rawlins SEARCH "SAND RAWLINS" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES