Here's a bit of the description of a recent TED talk entitled How to green the desert and reverse climate change:
Desertification is ... happening to about two-thirds of the world’s grasslands, accelerating climate change and causing traditional grazing societies to descend into social chaos. Savory has devoted his life to stopping it. He now believes -- and his work so far shows -- that a surprising factor can protect grasslands and even reclaim degraded land that was once desert.
It's more or less an argument that herd animal grazing patterns helps stop or even reverse desertification. He suggests using livestock to replace previous herd animals that were killed off and argues that only animals can really feed people from 95% of the world's land. Allan Savory also argues that doing such on half the world's grasslands would embed enough carbon in soils to drop environmental CO2 levels to pre-industrial concentrations. More info on this sort of argument here.
