The Great Green Wall's one of the world's most ambitious eco-projects. Is it working?

Women install barricades to halt the shifting dunes that threaten to swamp the oasis outside their village of Kaou, Chad. The oasis feeds their only source of farmland, but oases in the region have been shrinking steadily, elders say, in the face of hotter temperatures and stronger winds. The dune fixing is part of a broader intervention to support farming known as the Great Green Wall initiative.

It's a global effort with a multibillion dollar price tag. Among its aims: re-greening nearly 250 million acres, planting 4,000 miles of trees, helping farmers, creating jobs, sequestering carbon.

(Image credit: Tommy Trenchard for NPR)