[ExI] Greening the Sahara

[Mirco Romanato]

Dan ha scritto:

> I don't disagree. Drought is usually the result of what? Reduced
> rainfall?

In this case is cutting trees for wood that cause the soil to be exposed
to the sun and the wind, the sun dry the soil and the wind blow it away.
Then nothing is able to grow.




> See above. While that would be better, many areas have seasonal rains
> and are much greener that the Sahara. In my mind, it'd be easier to
> alter the rainfall via heating the desert than it would be to
> engineer year round rainfall.

I never wrote about engineering rainfalls; the engineering is to keep
the water that fall naturally from be lost.
If you have 2,5 cm years and keep the water from dispersing in the
underground, after a few years you have many cm of water near the
surface, but away from the sun.
You then concentrate the water in a few places and start grow trees
there (and edible vegetables too). Then profit eating and selling the
products. Then repeat the process until land is available.

> This might be true, though it doesn't necessarily mean all quick
> plans are wrong. The plan I propose might work. There's also a
> relative problem here. My proposal probably won't work in, say, a
> year -- save maybe to get some rain NOT to green the desert. It'll
> probably take several years to get some positive results.

> Finally, no reason it can't be coupled with other techniques.
> Increased rainfall will create a resource that could be use for other
> greening programs. It's not either/or here, but both/and.

Given that resources, money and skilled people are limited resources,
sometimes this is either/or.
I prefer to focus on programs that can sustain themselves in the short
time and produce a profit for the people involved, so they have a chance
to continue even when benefactors lose interests.

> All looks good, but I didn't see a clear indication of the costs...

I looked but I had found nothing.
It appear it is already used, anyway.

> Also, without having a good grasp of the costs of my proposal, I'm
> not sure I could, at this time, make a meaningful comparison. Still,
> one difference seems to be, magic sand and the like require a lot of
> infrastructure and it has to be put into place.

>From what I see, magic sand need only a oven and a way to mix the sand
with the additive that give it its properties. Nothing very high tech.

> The darkening to
> increase temperature might just involve dumping darker material or
> polluting the area. It might be cheaper and easier to carry out. (One
> could imagine a two step process: 1. darken and get rainfall
> increase, 2. use magic sand and similar techniques to hold it.)

The problem with darker the landscape is that the darkening stuff could
and would be blow away or covered by the sand.
The magic sand sheets would be put on site and covered. Then they would
work for 30 years minimum. No risk wind move it or cover it.
It, also, would work immediately on the limited place. No need to cover
a large part of the desert before seeing any effect.

The product is already used for saving water in the UAE and for other
purposes. They have already a plant operating in the production.

> True, but this would still take a long long time in most of the
> region, IMO.

Is this bad?
You would be able to start early with the magic sand, see the effect and
have people adapting to the new environment.
The Tuareg would have a problem to adapt in a few decades to a humid
climate. Or, maybe, they are forgotten out of the equation.




>> Citing Brian Wang:
>>>> As noted in a previous article about greening
>> deserts 75% of the
>>>> water for irrigation can be saved using the
>> nanosand and 85% of
>>>> water in the middle east and north africa is used
>> for irrigation.
>> 
>> So, using the nanosand it is possible to enlarge 4 time the land
>> irrigated.
> 
> This sounds good, though with greening the Sahara I'm thinking of
> enlarging this by perhaps a thousand-fold.

I think less. The desert don't start from the sea. A large part of the
place is steppes and savanna (at the borders).


Mirco