Volunteers and students plant trees and check on the green wall throughout the year. Growing a ‘great wall’ of trees may stop the Kubuqi desert from spreading. (Moon Lai)

We start walking up ridges as high as 10 staircases, slipping as the grains of sand tumble underfoot, grabbing a hand to keep from falling, pushing to get to the top of the next dune to see the sea of sand undulating in the distance.

“We are on the front line of a huge Chinese Dust Bowl advancing east,” says former South Korean ambassador to China Byong Hyon Kwon, an activist in the global fight against deserts on the move.

He is leading a group of volunteers across 21 / 2 miles of desert to a “green wall” of recently planted trees and shrubs aimed at blocking the march of sand and restoring the land. As recently as 50 years ago, this was grassland, Kwon says. People lived here and raised sheep.

But now the Kubuqi Desert is sucking away life. Windstorms threaten the air 800 miles away in Beijing and send plumes all the way across the Pacific to the West Coast of the United States.

Kwon founded Future Forest, a nonprofit organization, to combat desertification in 2001. As ambassador to China from 1998 to 2001, he had experienced firsthand the sandstorms known as the Yellow Dragon, which thicken the skies over Beijing with dust and send people with asthmatic lungs and weak hearts to the hospital. He became convinced then that if action weren’t taken, the march of sand would threaten the viability of the Asian continent.

Desertification poses major environmental and ecological threats to about one-third of the Earth, according to a 2004 United Nations study. China hopes to stop the spread of the Kubuqi desert by growing a great wall of trees. (Chris Gelken/Shirley Han Ying/Ridealist/Future Forest)

Creeping deserts are a global problem. About one-third of the Earth is exposed to desertification, according to a 2004 United Nations study. Large swaths of Africa and Asia are at risk, as are some parts of North America, especially in the American West. In a deadly dance involving polar melting, rising temperatures, degradation of the soil — from overuse and the clear-cutting of forests — and stress on water resources, the land gives way to sand.

What makes desertification so problematic in Asia is the movement of sand toward population hubs. The Gobi Desert in China’s northwest is the most dominant; its cousin, the Kubuqi, is farther east and closest to Beijing. To Kwon, the first battle station in the war against desertification is here in the Kubuqi.

With an annual budget of about $1 million, Future Forest has planted about 6.2 million trees since 2006. Every year, 30 percent of the new plants die and have to be replaced. When completed, the barrier of trees is to run north-south for about 10 miles, a green ribbon about a half-mile thick, as a choke point to divert the sands from their easterly path. The goal is to plant 100 million trees and thicken the green wall into habitable green space.

“We would like to stop the desertification here,” the ambassador says. “I’m convinced we can do it.”

We make it to a row of four-foot high trees, fragile-looking, dark green poplars that quiver in the constant wind. Our group is made up of students from China and South Korea, some of the volunteers who plant trees in the spring and then check on the green wall throughout the year, and a group of Harvard students who were in China, heard about the project and wanted to participate.

Growing a green wall takes years. Because the dunes move constantly in the wind, five-foot-square frames are set in the sand and then wired together to make a grid that is heavy enough not to get blown away. Trees are then planted inside the squares. Poplars are chosen in part because their roots, which grow like spider webs, can sprout more baby trees. If the tree survives, it should reach a man’s height in about four years. The volunteers also plant salix, a shrub that grows in sandy soil.

Kwon’s project is a small initiative in the larger strategy by governments in China and nongovernmental organizations to combat desertification.

Since the 1980s, the Chinese have planted billions of trees to bring back the land after decades of deforestation as the population grew and industrialization transformed the country. From 2000 to 2010, large swaths of land — equivalent to the size of Massachusetts — were reforested every year.

But these projects are controversial. In an article published in Yale University’s environmental magazine e360 last year, Jon R. Luoma wrote that some researchers are questioning “the long-term viability of significant aspects of China’s reforestation push.” Of particular concern is the use of nonnative species, whose high water needs can stress the area. An analysis by scientists at Beijing Forestry University suggested that up to 85 percent of the newly planted trees may ultimately fail, Luoma wrote.

Kwon wants to demonstrate that carefully selected local shrubs, trees and grasses can survive.“They tend to live better in sand than other trees,” says the ambassador’s son John, who is also working on the project.

With shrubs and trees come undergrowth, and slowly there are signs that the land may be coming back. We pass a foxhole, and one of the students finds an inch-long lizard. Underfoot I notice some tiny purple flowers: yang chai, a beach grass.

And then there are rows and rows of spindly trees. The volunteers start tagging the trees to honor donors and notables — and to allow monitoring of each tree by satellite. Barack Obama has tree No. 522. Lula da Silva (former Brazilian president), No. 508. Christiana Figueres (UN leader on climate change), No. 525.

“It’s great to be out here planting a tree — doing something,” says Jane Amero, a history of art major at Harvard.

The project is supported by the United Nations Convention to Combat Desertification. “Before” and “after” satellite images since 2006 show a general greening along the line of the barrier.

Is it enough to redirect the movement of sand? “I slow it down. I do not stop it totally,” Kwon says. If the effort fails, adds his son: “A Marslike surface may indeed be our future.”

Trafford, a former Washington Post writer, is author of “My Time: Making the Most of the Bonus Decades” and “As Time Goes By.”