Magnus Larsson: Turning dunes into architecture

83,170 views ・ 2009-11-26

TED


Please double-click on the English subtitles below to play the video.

00:15
It's a bit funny to be
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at a conference dedicated to things not seen,
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and present my proposal to build
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a 6,000-kilometer-long wall
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across the entire African continent.
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About the size of the Great Wall of China,
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this would hardly be an invisible structure.
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And yet it's made from parts that are invisible, or near-invisible, to the naked eye:
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bacteria and grains of sand.
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Now, as architects we're trained to solve problems.
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But I don't really believe in architectural problems;
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I only believe in opportunities.
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Which is why I'll show you a threat,
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and an architectural response.
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The threat is desertification.
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My response is a sandstone wall
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made from bacteria and solidified sand,
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stretching across the desert.
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Now, sand is a magical material
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of beautiful contradictions.
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It is simple and complex.
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It is peaceful and violent.
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It is always the same, never the same,
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endlessly fascinating.
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One billion grains of sand
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come into existence in the world each second.
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That's a cyclical process.
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As rocks and mountains die,
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grains of sand are born.
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Some of those grains may then cement naturally into sandstone.
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And as the sandstone weathers, new grains break free.
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Some of those grains may then accumulate
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on a massive scale,
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into a sand dune.
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In a way, the static, stone mountain
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becomes a moving mountain of sand.
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But, moving mountains can be dangerous. Let me try and explain why.
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Dry areas cover more than one third of the Earth's land surfaces.
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Some are already deserts;
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others are being seriously degraded by the sand.
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Just south of the Sahara we find the Sahel.
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The name means "edge of the desert."
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And this is the region most closely associated with desertification.
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It was here in the late '60s and early '70s
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that major droughts brought three million people
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to become dependent upon emergency food aid,
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with about up to 250,000 dying.
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This is a catastrophe waiting to happen again.
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And it's one that gets very little attention.
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In our accelerated media culture,
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desertification is simply too slow
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to reach the headlines.
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It's nothing like a tsunami or a Katrina:
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too few crying children and smashed up houses.
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And yet desertification
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is a major threat on all continents,
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affecting some 110 countries
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and about 70 percent of the world's agricultural drylands.
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It seriously threatens the livelihoods
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of millions of people,
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and especially in Africa and China.
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And it is largely an issue that we've created for ourselves
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through unsustainable use of scarce resources.
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So, we get climate change.
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We get droughts,
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increased desertification,
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crashing food systems, water scarcity,
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famine, forced migration,
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political instability, warfare, crisis.
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That's a potential scenario
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if we fail to take this seriously.
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But, how far away is it?
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I went to Sokoto in northern Nigeria
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to try and find out how far away it is.
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The dunes here move southward at a pace of around 600 meters a year.
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That's the Sahara eating up almost [two meters] a day of the arable land,
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physically pushing people away from their homes.
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Here I am -- I'm the second person on the left --
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(Laughter)
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with the elders in Gidan-Kara,
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a tiny village outside of Sokoto.
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They had to move this village in 1987
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as a huge dune threatened to swallow it.
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So, they moved the entire village, hut by hut.
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This is where the village used to be.
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It took us about 10 minutes to climb up to the top of that dune,
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which goes to show why they had to move to a safer location.
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That's the kind of forced migration
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that desertification can lead to.
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If you happen to live close to the desert border,
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you can pretty much calculate how long it will be
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before you have to carry your kids away,
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and abandon your home and your life as you know it.
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Now, sand dunes cover only about one fifth of our deserts.
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And still, those extreme environments are very good places
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if we want to stop the shifting sands.
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Four years ago, 23 African countries
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came together to create the Great Green Wall Sahara.
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A fantastic project, the initial plan
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called for a shelter belt of trees to be planted
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right across the African continent,
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from Mauritania in the west, all the way to Djibouti in the east.
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If you want to stop a sand dune from moving,
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what you need to make sure to do is to stop the grains
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from avalanching over its crest.
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And a good way of doing that, the most efficient way,
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is to use some kind of sand catcher.
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Trees or cacti are good for this.
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But, one of the problems with planting trees is that
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the people in these regions are so poor
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that they chop them down for firewood.
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Now there is an alternative to just planting trees
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and hoping that they won't get chopped down.
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This sandstone wall that I'm proposing essentially does three things.
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It adds roughness to the dune's surface,
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to the texture of the dune's surface, binding the grains.
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It provides a physical support structure for the trees,
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and it creates physical spaces,
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habitable spaces inside of the sand dunes.
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If people live inside of the green barrier
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they can help support the trees, protect them from humans,
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and from some of the forces of nature.
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Inside of the dunes we find shade.
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We can start harvesting condensation,
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and start greening the desert from within.
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Sand dunes are almost like ready-made buildings in a way.
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All we need to do is solidify the parts that we need to be solid,
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and then excavate the sand,
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and we have our architecture.
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We can either excavate it by hand
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or we can have the wind excavate it for us.
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So, the wind carries the sand onto the site
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and then it carries the redundant sand away from the structure for us.
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But, by now, you're probably asking,
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how am I planning to solidify a sand dune?
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How do we glue those grains of sand together?
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And the answer is, perhaps, that you use these guys,
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Bacillus pasteurii,
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a micro-organism that is readily available in wetlands
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and marshes, and does precisely that.
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It takes a pile of loose sand
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and it creates sandstone out of it.
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These images from the American Society for Microbiology show us the process.
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What happens is, you pour Bacillus pasteurii onto a pile of sand,
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and it starts filling up the voids in between the grains.
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A chemical process produces calcite,
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which is a kind of natural cement
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that binds the grains together.
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The whole cementation process takes about 24 hours.
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I learned about this from a professor at U.C. Davis called Jason DeJong.
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He managed to do it in a mere 1,400 minutes.
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Here I am, playing the part of the mad scientist,
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working with the bugs at UCL in London,
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trying to solidify them.
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So, how much would this cost?
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I'm not an economist, very much not,
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but I did, quite literally, a back of the envelope calculation --
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(Laughter)
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-- and it seems that for a cubic meter of concrete
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we would have to pay in the region of 90 dollars.
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And, after an initial cost of 60 bucks to buy the bacteria,
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which you'll never have to pay again,
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one cubic meter of bacterial sand
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would be about 11 dollars.
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How do we construct something like this?
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Well, I'll quickly show you two options.
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The first is to create a kind of balloon structure,
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fill it with bacteria, then allow the sand to wash over the balloon,
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pop the balloon, as it were, disseminating the bacteria into the sand and solidifying it.
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Then, a few years afterwards,
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using permacultural strategies,
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we green that part of the desert.
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The second alternative would be to use injection piles.
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So, we pushed the piles down through the dune,
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and we create an initial bacterial surface.
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We then pull the piles up through the dune
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and we're able to create almost any conceivable shape inside of the sand
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with the sand acting as a mold as we go up.
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So, we have a way of turning sand into sandstone,
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and then creating these habitable spaces inside of the desert dunes.
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But, what should they look like?
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Well, I was inspired, for my architectural form, by tafoni,
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which look a little bit like this, this is a model representation of it.
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These are cavernous rock structures that I found on the site in Sokoto.
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And I realized that if I scaled them up, they would provide me
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with good spatial qualities,
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for ventilation, for thermal comfort, and for other things.
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Now, part of the formal control over this structure
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would be lost to nature, obviously,
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as the bacteria do their work.
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And I think this creates a kind of boundless beauty actually.
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I think there is really something in that articulation
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that is quite nice.
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We see the result, the traces, if you like,
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of the Bacillus pasteurii being harnessed to sculpt the desert
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into these habitable environments.
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Some people believe that
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this would spread uncontrollably,
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and that the bacteria would kill everything in its way.
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That's not true at all.
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It's a natural process. It goes on in nature today,
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and the bacteria die as soon as we stop feeding them.
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So, there it is --
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architectural anti-desertification structures
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made from the desert itself.
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Sand-stopping devices, made from sand.
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The world is likely to lose one third of its arable land
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by the end of the century.
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In a period of unprecedented population growth
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and increased food demands, this could prove disastrous.
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And quite frankly, we're putting our heads in the sand.
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If nothing else, I would like for this scheme to initiate a discussion.
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But, if I had something like a TED wish,
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it would be to actually get it built,
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to start building this habitable wall,
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this very, very long, but very narrow city in the desert,
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built into the dunescape itself.
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It's not only something that supports trees,
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but something that connects people and countries together.
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I would like to conclude by showing you an animation of the structure,
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and leave you with a sentence by Jorge Luis Borges.
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Borges said that "nothing is built on stone,
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everything is built on sand,
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but we must build as if the sand were stone."
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Now, there are many details left to explore in this scheme --
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political, practical, ethical, financial.
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My design, as it takes you down the rabbit hole,
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is fraught with many challenges
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and difficulties in the real world.
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But, it's a beginning, it's a vision.
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As Borges would have it, it's the sand.
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And I think now is really the time
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to turn it into stone. Thank you.
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(Applause)
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