Enterprising Swedish architect Magnus Larsson, already well-known in the field thanks to his proposed Great Green Wall, a 4,349 mile line of trees stretching across Africa to stop desertification. In a plan  presented this week at at the TEDGlobal confererence in Oxford, Larsson is fortifying his Great Green Wall with a complementary proposal to halt desertification: a 3,728 mile long sandstone wall that bisects Africa from Djibouti in the east to Mauritania in the west.
The sandstone wall would provide physical support for the trees as well as a barrier if they are ever removed. It would be created by binding sand grains together using Bacillus pasteurii, a bacterium found in wetlands that produces a natural cement-like material called calcite. In Larsson's vision, sand dunes could be injected with the bacteria or big bacteria-filled balloons could be unleashed and eventually popped when moving sand dunes begin to encroach. When complete, the structure could provide shade and act as a water-collection point for nearby populations.
There are, of course, numerous practical, financial, and political considerations to deal with before Larsson's project can even begin to get off the ground. But it's a promising vision that at least provides us with a blueprint to stop the desert from creeping into the lives of unsuspecting Africans. And Larsson isn't alone in his vision: China is also planning a wall of trees to halt the growing Gobi Desert.