Without wishing to spoil the ending, this chap has some very simple ideas on how to turn the world's deserts back in to habitable land, with water and much grazing for animals.  And not just ideas - he has spent 20 years putting these ideas in to practice, and large swathes of Africa are now no longer starving because of this chap.

We're lost a startling amount of land over the last few hundred years to deserts due to our own impacts on the world.  The key to greening these areas again is treating the land as it once was by the huge herds of herbivores.  

The results are absolutely incredible.

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Allan Savory
Green Deserts
Reverse Climate Change