Can the Great Green Wall change direction?

Story highlights

  • Great Green Wall would be world's largest living structure
  • The 4,700-mile long line of trees would stop Sahara's advance
  • Local projects in Niger have delivered spectacular success

(CNN)A 7,700-kilometer wall of trees, running through 11 countries along the southern frontier of the Sahara Desert.

That's what the African Union proposed in 2007, a "Great Green Wall" that was to be the largest living structure on the planet.
    The purpose was to provide a mighty barrier against the advance of the Sahara, and to reverse the plague of desertification spreading drought, famine and poverty through the Sahel region.
      The Great Green Wall Initiative for the Sahara and Sahel Initiative (GGWSSI) has since gained rocket boosters. Today, the Initiative has 21 African countries participating, over $4 billion of pledged funding, and heavyweight partners from the World Bank to the French government.
      The projects has sky-high ambitions; to restore 50 million hectares of land, provide food security for 20 million people, create 350,000 jobs, and sequester 250 million tons of carbon.
      Work is already well underway. The GGWSSI recently claimed that 15% of trees have been planted, largely in Senegal, with four million hectares of land restored.
      But the grand vision rests on a suspect premise.
      Wall of trees in Senegal, where much of the planting has taken place.

      Desert diagnosis

      There is a consensus among scientists that that the Sahara Desert is not advancing.
      "The southern edge of the Sahara Desert moves up and down according to long-term climate cycles," says Dr. Jonathan Davies, head of the Global Drylands Initiative at the International Union for the Conservation of Nature (IUCN). "