The scheme, put forward by architect Magnus Larsson at the TED Global 2009 conference in Oxford, England, would use a bacterium that can solidify sand within a matter of hours.

Larsson told the BBC that Bacillus pasteurii, commonly found in wetlands, can bind sand grains together to basically create sandstone.

He proposes injecting the dunes with it on a massive scale or using a barrage of giant bacteria-filled balloons to create the Sahara barrier.

"We allow the dune to wash over this structure then we would pop the balloon," Larsson said. A 2007 U.N. report warned that expanding deserts threaten one-third of the Earth’s population.

The barrier, proposed by Larsson, would stretch from Mauritania in the west of Africa to Djibouti in the east.

Earlier proposals to create a wall of trees to halt the advance of the desert are considered impractical because people in such arid regions are usually so poor that they would chop the trees down for firewood.

Photo: DUNE: Arenaceous Anti-Desertification Architecture