(CNN)The world's largest desert is growing. In the last century, the Sahara Desert expanded by more than 10%, now covering an area of more than 3.3 million square miles (8.6 million square kilometers) and spanning 11 countries in North Africa.
The Sahel region, a semi-arid belt that acts as a buffer zone just south of the desert, is most affected. Water, already scarce, is becoming scarcer. Soil quality is deteriorating, and a lack of vegetation is leading to food insecurity. The UN estimates roughly 135 million people who depend on these degraded lands are at risk.
But an ambitious plan, launched by the African Union in 2007, could help to hold back the hot sands and protect the Sahel communities. Within the next decade, the Great Green Wall initiative hopes to restore 100 million hectares of land between Senegal in the west and Djibouti in the east, creating a 15-kilometer-wide (9 miles) and 8,000-kilometer-long (5,000 miles) mosaic of trees, vegetation, grasslands and plants.

Having previously struggled with insufficient and unpredictable funding, the project received a major boost in January: $14 billion in new funding from France, the World Bank and other donors -- contributing nearly half of the $33 billion the UN estimates is needed to achieve the 2030 goal.

If completed in full, the wall will be more than three times the length of the Great Barrier Reef, currently the largest living structure on Earth.
Fresh shoots
Nine years away from its deadline, there is still a long way to go. So far, 4 million hectares of land has been restored -- just 4% of the overall goal -- though this rises to almost 20 million hectares when counting areas outside of the official Great Green Wall zones.
Countries have tried a variety of conservation measures, such as reforestation, agroforestry, creating terraces, and dune fixing -- a technique that prevents the movement of sand long enough to let natural vegetation establish itself. They are also taking steps to protect water supplies, by drilling bore holes and building irrigation systems.

Ethiopia is reported to have restored the most so far, producing 5.5 billion plants and seedlings, and planting more than 150,000 hectares of reforested lands and 700,000 hectares of terraces -- which together make up an area more than five times the size of London.

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