TED Talk, November 2009
It's a bit funny to be at a conference
dedicated to things not seen
and present my proposal to build
a six-thousand-kilometer-long wall
across the entire African continent.
About the size of the Great Wall of China,
this would hardly be an invisible structure.
And yet it's made from parts that are invisible,
or near-invisible, to the naked eye:
bacteria and grains of sand.
Now, as architects we're trained to solve problems.
But I don't rely believe in arquitectural problems;
I only believe in opportunities.
Which is why I'll show you a threat,
and an architectural response.
The threat is desertification.
My response is a sandstone wall
made from bacteria and solidified sand,
stretching across the desert.
Now, sand is a magical material
of beautiful contradictions.
It is simple and complex.
It is peaceful and violent.
It is always the same,
never the same
always fascinating.
One billion* grains of sand
(*: the anglo billion has nine zeros…a thousand million)
come into existence in the world each second.
That's a cyclical process.
As rocks and mountains die,
grains of sand are born.
Some of those grains may
then cement naturally into sandstone.
And as the sandstone weathers,
new grains break free.
Some of those grains may then
accumulate on a massive scale,
into a sand dune.
In a way, the static, stone mountain
becomes a moving mountain of sand.
But, moving mountains
can be dangerous.
Let me try and explain why.
Dry areas cover more than
one third of the Earth's land surface.
Some are already deserts;
others are only being seriously
degraded by the sand.
Just south of the Sahara we find the Sahel.
The name means "edge of the desert".
And this is the region
most closely associated
with desertification.
It was here in the late sixties and early seventies
that major droughts brought three million people
to become dependent upon emergency food aid,
with about up to 250,000 dying.
This is a catastrophe waiting to happen again.
And it's one that gets very little attention.
In our accelerated media culture,
desertification is simply too slow
to reach the headlines.
It's nothing like a tsunami or a Katrina:
too few crying children and smashed up houses.
And yet, desertification
is a major threat in all continents,
affecting some 110 countries
and about 70 per cent
of the world's agricultural drylands.
It seriously threatens the livelihoods
of millions of people,
and especially in Africa and China.
And it is largely an issue
that we've created for ourselves
through unsustainable
use of scare resources.
So, we get climate change.
We get droughts,
increased desertification,
crashing food systems,
water scarcity, famine,
forced migration,
political instability,
warfare, crisis.
That's a potential scenario
if we fail to take it seriously.
But, how far away is it?
I went to Sokoto in northern Nigeria
to try to find out how far away it is.
The dunes have move southward
at a pace of around 600 meters a year.
That's the Sahara eating up
almost [two meters] a day of arable land,
physically pushing people away from their homes.
Here I am, with the elders in Gidan-Kara,
a tiny village outside of Sokoto.
They had to move this village in 1987
as a huge dune threatened to swallow it.
So, they moved the entire village, hut by hut.
This is where the village used to be.
It took about 10 minutes to climb up
to the top of the dune, which goes to show
why they had to move to a safer location.
That's the kind of force migration
the desertification can lead to.
If you happen to live close to the desert border,
you can pretty much calculate how long it will be
before you have to carry your kids away,
and abandon your home and your life as you know it.
Now, sand dunes cover only
about one fifth of our deserts.
And still, those extreme environments
are very good places if we want
to stop the shifting sands.
Four years ago, 23 African countries
came together to create
the Great Green Wall Sahara.
A fantastic project,
the initial plan call for a shelter belt
of trees to be planted
right across the African continent,
from Mauritania in the west,
all the way to Djibouti in the east.
If you want to stop a sand dune from moving,
what you need to make sure to do is to stop
the grains from avalanching over its crest.
And a good way of doing that,
the most efficient way,
is to use some kind of sand catcher.
Trees or cacti are good for this.
But one of the problems of planting trees
is that the people in these regions are so poor
that they chop them down for firewood.
Now there is an alternative to just planting trees
and hoping that they won't get chopped down.
This sandstone wall that I'm proposing
essentially does three things.
It adds roughness to the dune surface,
to the texture of the dune's surface, binding the grains.
It provides
a physical support structure for the trees,
and it creates physical spaces,
habitable spaces inside the sand dunes.
If people live inside the green barrier
they can help support the trees,
protect them from humans,
and from some of the forces of nature.
Inside of the dunes we find shade.
We can start harvesting condensation,
and start greening the desert from within.
Sand dunes are almost like
ready-made buildings in a way.
All we need to do is solidify
the parts that we need to be solid,
and to excavate the sand,
and we have our architecture.
We can either excavate it by hand
or we can have the wind excavate it for us.
So, the wind carries the sand onto the site
and then it carries the redundant sand
away from the structure for us.
But, by now, you're probably asking
how I am planning to solidify a sand dune?
How do we glue those grains of sand together?
And the answer is, perhaps,
that you use these guys, Bacillus pasteurii,
a micro-organism that is readily available
in wetlands and marshes, and does precisely that.
It takes a pile of loose sand
and it creates sandstone out of it.
These images from
the American Society of Microbiology
show us the process.
What happens is,
you pour Bacillus pasteurii
onto a pile of sand,
and it starts filling up
the voids in between the grains.
A chemical process produces calcite,
which is a kind of natural cement
that binds the grain together.
The whole cementation process
takes about, one day, 24 hours.
I learned about this from a professor
at the University of California at Davis
called Jason DeJong.
He managed to do it
in a mere 1,400 minutes
(less than 24 hours).
Here I am, playing
the part of a mad scientist,
working with the bugs
at the University College in London
trying to solidify them.
So how much would this cost?
I'm not an economist, very much not,
but I did, quite literally,
a back of the envelope calculation
and it seems that for a cubic meter
of concrete we would have to pay
in the region of 90 dollars.
And, after an initial cost
of 60 bucks to buy the bacteria,
which you'll never have to pay again,
one cubic meter of bacterial sand
would be about 11 dollars.
How do we construct something like this?
Well, I'll quickly show you two options.
The first is to create
a kind of balloon structure,
fill it with bacteria,
then allow the sand
to wash over the balloon,
pop the balloon, as it were,
disseminating the bacteria
into the sand and solidifying it.
Then, a few years afterwards,
using permaculture strategies,
we green that part of the desert.
The second alternative
would be to use injection piles.
So, we pushed the piles down
through the dune,
and we create an initial bacterial surface.
We then pull the piles up through the dune
and we're able to create almost
any conceivable shape inside of the sand
with the sand acting as a mold as we go up.
So we have a way of turning sand into sandstone,
and then creating these habitable spaces
inside the desert dunes.
But, what should they look like?
Well, I was inspired,
for my architectural form,
by tafoni, which looks like this,
this is a model representation of it.
These are cavernous rock structure
that I found on the site in Sokoto.
And I realized that if I scaled them up,
they would provide me with good spatial qualities,
for ventilation, for thermal comfort, and for other things.
Now, part of the formal control over this structure
would be lost to nature, obviously,
as the bacteria do their work.
And I think this creates a kind
of boundless beauty actually.
I think there is really something
in that articulation that is quite nice.
We see the result,
the traces, if you like,
of the Bacillus pasteurii
being harnessed to sculpt the desert
into these habitable environments.
Some people believe
that this would spread uncontrollably,
and that the bacteria would kill
everything in its way.
That's not true at all.
It's a natural process.
It goes in nature today,
and the bacteria die
as soon as we stop feeding them.
So, there it is
-architectural anti-desertification structures
made from the desert itself.
Sand-stopping devices, made from sand.
The world is likely to los
one third of its arable land
be the end of the century.
In a period of unprecedented population growth
and increased food demands, this would prove disastrous.
And quite frankly, we're putting our heads in the sand.
If nothing else, I would like
for this scheme to initiate a discussion.
But, if I had something like a TED wish,
it would be actually get it built,
to start building this habitable wall,
this very, very long, but very narrow city
in the desert, built into the dunescape itself.
It is not only something that supports trees,
but something that connects
people and countries together.
I would like to conclude
by showing you an animation
of the structure, and leave you
with a sentence of Jorge Luis Borges.
Borges said that
"nothing is built of stone,
everything is built on sand,
but we must build
as if the sand were stone."
Now, there are many details
left to explore in this scheme
-political, practical, ethical, financial.
My design, as it takes
you down the rabbit hole,
is fraught with many challenges
and difficulties in the real world.
But, it's a beginning, it's a vision.
As Borges would have it, it's the sand.
And I think now is really the time
to turn it into stone.
Thank you.
____
Here's another solution
to building structures
in the sand alongside the bacteria...
Apr 18 2013: Magnus, or Others: Take this concept of BIOassisted architecture a step further use ANTS as the bacteria delivery system: to mine the dunes
There are probably no ants in the dune system because the dunes move and there is not adequate food for them to colonize the dunes. Ants are great at moving sand and they have a pattern of tunnels that each species creates. If they could learn that carrying the bacteria into a sand space would solidify that space then they would adapt that to their architectural creations. You could use a less costly way to deliver the ants, a food supply, and the bacteria supply. It could even develop that the ants would evolve a symbiotic relationship with the bacteria as some species have with aphids. Why not consult a biologist about the possibilities and suggestions for likely candidates. The ants might be just the parameter to help create the micro-ecologies that would help provide richer soil, moisture retention, and other benefits that would speed the project along and add greater sustainability. Yes, there would have to be some kind of controls such that the ants don't overwhelm things, but rather establish a useful and beneficial presence even as they now do in many world ecologies. It could be that more than one species of ant would be needed to accomplish the task.
Another feature is that the process could be carefully studied in a laboratory environment in terrariums before ever introducing it into the wild. Ants have a relatively short life cycle. If only the drones worked with the bacteria, the queen and males could start new colonies, but the symbiosis would be broken and the new colonies would not flourish unless the bacteria were introduced in some way.
____
More on the comments that follow Magnus Larsson
presentation at TED Talk
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