Hi Hicksd,
the algae-option was something that was reported on TV some time ago. Seems it's not that good, because if you want to achieve a considerable effect, you have to create masses of algae which would harm the existing ecosystem a lot. For the other things I'll have a closer look at. My intuition is that way that too much tech may not be the solution. But hey! Better look twice before throwing away a possible solution.
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I saw a video of Allan Savory these days(
YouTube). He's very enthusiastic about reversing desertification of land. After a major fail he got to a possible solution which helps with climate change to.
His theory for one reason for desertification(in areas with only partial humidity) is dry micro climate directly on the surface of the soil. Once there where many herds of wild animals, because a large herd can better defend against hunting packs of wolves for example than single animals or small groups. Even those large herds kept moving quickly to not get in danger of gathering hunting packs. So they grazed the lands intensely for a short period of time, moved on, came back a lot later to eat here again. So the vegetation can regenerate extensively between the use-cycles. The animals left their excrements, which was furtilizing the soil and they trampled down the grass. The trampled down grass covers the soil, so the water is held back within the soil and is not evaporating as it would be if uncovered. The trampled down grass is further dying, making room for the next generation of grass.
Since there are no longer large herds of wild animals due to excessive hunting of man, this process of conservation micro climate ceased to exist, and Savory thought about what can be done, to achive the same by maybe mimicking nature as it once was. So he had the idea of moving large flocks of livestock upon the living grasslands and got them moved on to other areas in a special rotation which imitates the original use.
It seems to work out very fine. The quality of the soil improved drastically. Some farms do not even need extra fertilizer to have the same crops as with fertilizer added. Knowledge is spreaded and some farmers begin to try it for themselves.
The method is interesting because it's really low tech. The movement is accomplished via electric fences, but can also done with manpower if the former tools are not available. Even in Africa there are projects to teach that knowledge to locals in order to transform desertification into prospering nature. The advantage for climate is that increased biomass binds co2 and get's it into the soil.(Layers of dead grass vegetation. Maybe the co2 of vegetation is released into the air, because of decay. Did not get all details so far.)
Update
Pleasant to see that Savorys idea(which seems to be originated in France in the 1950s) is spreading. I saw a talk from the austrian Beatrice Kehl(degree in landscape architecture) talking in a major german community project about her successful experiences on this method she made in great britain. A way of unterstanding nature and doing it right.