KEBEMER, Senegal (AP) — The Great Green Wall that was once envisioned as a way for Africa to fight climate change has stalled. The project aimed to plant a 5,000-mile line of trees that would span the entire continent and hold back the Sahara Desert. The trees were supposed to prevent the desert sands from advancing into temperate agricultural regions. The effort began in 2007. But as temperatures rose and rainfall diminished, millions of the planted trees died. Now only 4% of the wall’s original goal has been met. Organizers have shifted their focus from planting a wall of trees to trying a mosaic of smaller projects to stop the expanding desert.