A grand vision for a wall of vegetation reaching thousands of miles across Africa and slowing the spread of the Sahara Desert took a step closer to becoming a reality yesterday with the first international conference to discuss how to bring it about.

The Great Green Wall would be a nine-mile wide band of trees and shrubbery across the southern border of the Sahara’s southern Sahel desert, stretching 4,400 miles through 11 countries from the Senegalese capital of Dakar in the west to Djibouti on the Indian Ocean coast.