Can Bacteria Create a Cement Wall to Hold Back the Sahara?

By Eliza Strickland | July 27, 2009 1:04 pm

Sahara dunesTo stop the spread of the Sahara Desert, one innovative thinker has proposed a bold plan: a wall along the southern border of the desert that would hold back the advancing dunes. Swedish architect Magnus Larsson says the wall would effectively be made by “freezing” the shifting sand dunes, turning them into sandstone. “The idea is to stop the desert using the desert itself,” he said. The sand grains would be bound together using a bacterium called Bacillus pasteurii commonly found in wetlands.” It is a microorganism which chemically produces calcite – a kind of natural cement” [BBC News].

Larsson is 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 [Fast Company]. The sandstone wall could compliment the green wall, Larsson says, because if people chopped down the trees for firewood the sandstone wall would still remain.

The architect unveiled his proposal at the TEDGlobal conference in Oxford, dedicated to “ideas worth spreading.” Larsson explained that the bacterium would get into the dunes either by injecting it (on a massive scale) or by giant balloons filled with it — these would be place in the way of the moving dunes, which would wash over the balloons, which in turn would be popped allowing the bacteria to get into the sand [Treehugger].

Larsson acknowledges that the scheme faces political, practical, financial, and ethical challenges. “However, it’s a beginning, it’s a vision; if nothing else I would like this scheme to initiate a discussion,” he added [BBC News].

Related Content:
80beats: Architects Propose Fantastic Greenhouses Across the Sahara
80beats: A Solar Power Plant in the Sahara Could Power All of Europe
DISCOVER: How to Make a Desert

Image: flickr / kashmir

CATEGORIZED UNDER: Environment, Living World, Technology
  • Jumblepudding

    I wonder if there is evidence that this type of sandstone formation has happened naturally in the past during the wetter cycles in the sahara.

  • Shaithis

    Mankind has clearcut entire forest. We’ve damned rivers and redirected mighty streams. We’ve dreadged oceans to hold back the tides. There are countless examples of how man has shaped his environment to his own design, but there has alway’s been a negative impact for each an everyone. Holding back the advancing dunes of the mighty Sahera desert. I wonder what the impact of that will be.

  • Brian

    @Shaithis,

    That’s a pretty negative viewpoint, don’t you think? I agree that some interventions by mankind in nature have had problems, and others have been outright disasters. However EVERY change by man is bad? Really? You want a second chance to consider that statement?

    Larsson is proposing a couple of ideas to limit the desert, and desertification as a process. You’d have a point if the desert were a disappearing biome, but it isn’t. The Sahara is the world’s largest desert and it’s been growing for centuries. In fact there are numerous archeological sites documenting times of growth and plenty, in areas that are in the deep desert now. Some of these sites are thousands of years old.

    In general water means life. The desert lacks water and is thus severely limited in how much life it can support. The lack of water and continuous desertification causes hardship and starvation in the Sahel region surrounding the Sahara. That’s for all animals and plants, not just the humans living there.

    One more point. Way back, decades ago, the Chinese government sponsored an effort to plant millions of trees around Beijing. This area is subject to dust storms and hot, dry winds coming off the Gobi desert. The Chinese were successful and planted so many trees that they altered the local climate. The result was a more livable capital city, but that’s not all. The climate cannot be limited and thus the entire region benefits, including all animals and plants in the area.

    Larsson deserves a little better than “mankind is bad. Bad!!”.

  • Carter

    I hope those wetlands bacteria can actually survive in the desert. But my biggest concern is that the wall would do nothing to prevent arid conditions from spreading south of the Sahara – an ongoing process not caused by sand dunes advancing, which happens as a result of prevailing winds causing sediment transport.

    I think this scientist ought to focus on ecology to restore these areas, as desertification happens most rapidly when there are no root systems laid down by species that can tolerate dry conditions. These root systems prevent topsoil erosion and the plants of course create habitat for a range of other species – plants, animals, fungi, etc.

  • Matt T

    @ Carter: I doubt that preventing the advance of the sand dunes would do NOTHING to prevent arid conditions from moving as well. All that dry sand is probably acting like a sponge, soaking up all the available humidity. If you prevent the sand dunes form moving south, I would think that it would at least have some effect on the hygrometer.

    @ Brian: Well put. Martians had this same debate a couple of years ago, and look what happened to that place.

  • Stphen Klaber

    While such a wall would clearly reduce the wind/sand damage at the edge of the desert, it doesn’t address the real problems, which have to do with water.

    The war against the desert must be won in the wetlands. The enemy still has the initiative. He has completely overrun the entire Eastern portion of the Lake Chad basin, most of the lake itself and is well established in the western tributaries, meeting sporadic resistance in Nigeria. I’ve read reports of a start of organized resistance in Mauritania. Typha Australis (southern cattail) is the shock army of the desert. It, and its cousins (Typha spp.) are quickly overrunning the African continent, Asia, and Australia. It has allies: Phragmites, hyacinth, water lettuce… In the area relevant to the Sahara’s expansion, we are talking upwards of 5 million hectares. There is a lot of weeding to be done.

    Typha is a dessication machine and a siltation machine. Its presence (cover) more than quadruples the evapotranspiration losses in a body of water. The silt it produces raises the stream or lake bed until it is no longer viable. Every change we make to a body of water creates some place where the water level has changed to favor weed growth. Dams and irrigation accelerated the natural process called hydrosere beyond what could be naturally recovered from during a drought.

    We must clear these weeds! They are killing off whole continents. Their resilience makes clearing them a never ending process. The biofuels market provides a way to finance the job. From charcoal to ethanol, Typha is good feedstock. This is the one biofuel source which improves your water supply.

    Picture the Sahara, stopped and shrunk. Picture the Sahel greener, healthier. Picture Lake Chad restored. IT CAN BE! What’s in the way is some weeds: 5-10 million hectares of them.

  • Lewis Brand

    I think this an interesting, if a little odd idea. Even if it could be done, the “wall” would have to become a manmade mountain range in order to succeed, i.e it would have to be at least 20 miles wide and 3000 feet high!
    I am not a cynic, but this does sound a bit like plugging an active volcano with a vast pouring of concrete!
    Even if you manage that, another crack will appear.

  • http://deleted Rasselas

    Is it a consideration that the bacterium could spread and affect more of the desert than just the border edges? It has to spread a little I would think, or it wouldn’t work… so how do we know it wouldn’t spread more than anticipated (especially considering the winds of the desert)?

    The other problem is… how easy would it be to remove these mountains later on?

    A question of Stephen Klaber… how invasive are those plant species? If the climate were wetter, would they be supplanted by more native/healthy species, or would they continue to spread?

    A Desert is:
    1) Hot (daytime, cool at night… but the heat is the bigger problem, though fluctuation is contributive)
    2) DRY [the main consideration]
    3) Shifty (windy, usually anyways)
    4) Sandy (as opposed to healthy soil)
    5) Barren (lifeless of plants and animals on the whole) [organisms are typically +80% water]

  • Kim

    Another concern is can the Sahara spread south? The wind might hit the wall and reverse, so yes Shatihis could be right . There could be a negative effect on this plan.

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