[ExI] Greening the Sahara

[Dan]

On Monday, July 20, 2009 3:00:05 PM Mirco Romanato painlord2k at libero.it wrote:
> 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.

I'm not sure that's the case for the whole Sahara. From my readings, it seems to have been a long period of drying out that led to a succession of ever more arid regimes. Maybe I've misunderstood here, but it seems the model you have is human clearcut the whole region? I'd agree that there was non-human deforestation -- mainly lower rainfall and probably more forest fires with grasses taking over, pushing out trees, but then the area becoming too dry even for grasses.

>> 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;
 
I was commenting merely on my proposal here -- not yours.
 
> the engineering is to keep
> the water that fall naturally from be lost.
 
Yes, and, again, no reason to not do both: engineer to get higher rainfalls and engineer to conserve (or put to good use) the rain that has fallen.

> 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.
 
No disagreement from me here.

> 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.
 
Or soak the whole region and still have engineering projects in tiny areas that'll act as catalysts to regrow forests in the region.

>> 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.
 
Well, for now, I'm speculating, so I don't have a clue on the costs. But if you want another project, flood the East Africa Rift valley seems really cheap and relatively quick. It requires merely opening a small channel in the extreme northern part of that valley to allow the Red Sea to trickle in at a higher rate than now.

> 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.
 
Understood.

>> 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.
 
Ah, there's the rub: we don't know. And we don't know if they can easily be scaled up. I also fear some of this is government-subsidized, so it might not be self-sustaining but merely subsidized.

[snip]
> The problem with darker the landscape is that the darkening
> stuff could and would be blow away or covered by the sand.
 
Yes, I've already mentioned this. And mentioned two ways to deal with this.
 
> 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.
 
But what happens if it's covered by sand? :)

[snip]
> 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.

Not at all. You're treating my proposal as if it were a big government project. I'm just throwing out the idea -- not saying it must be done or must be done my way.

>> 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).

In some areas, true; in others not. The Sahara is huge, though. Merely doubling or tripling or tenfolding the oases is not what I'm looking for -- though that'd be nice.
 
Regards,
 
Dan