We no longer have the number of massive herds of animals that used to roam the plains/savannahs grazing, pooing and to a lesser extent escaping from predators.
This has meant that the grasslands are no longer trampled on and "fertilised". This has caused the grasses to die back, the soil to degrade, to not hold water and to turn to desert. (see the sahara, the outback, parts of china and the usa).
Subsequently we've tried to be really careful with the land and not over graze it etc. which tends to have the opposite effect than what is desired.
Now I also looked into reforestation because I thought trees were the answer. Grow trees sequester carbon etc. But it turns out the cost of doing this £/$ and water (desalination) would actually be outweighed by both the albido effect (green trees absorb more sunlight than deserts that reflect it back) and that trees don't really grow fast enough to have the impact required.
Getting back to the grasslands, it turns out that when you intensively drive a herd over grasslands the grass initially dies back but the root system expands, the plant grows quickly and sequesters carbon into the ground. It actually builds soil and traps carbon and it does it faster than previously thought. The ground is also more permeable to water so when big storms come it actually soaks up the water for later use rather than it running off and causing floods, erosion etc. Also grass is lighter (colour) than trees so the albido effect is not so bad.
This is just my understanding of one part of the problem. This is what I think may be a solution to that:
We need to change the way we manage livestock. Probably change legislation so they can't be kept indoors or feed grains (I think that is a big methane contributor as well). We should have grazing plans for entire countries that manage existing land well and restore broken land. We should stop eating them because we need a big herd to restore the land and we probably need to employ a lot of people to drive the herds (yeeha).
Grazing plans are simple, illiterate people seem to cope fine with them. We've got the technology to scale this and in the west we probably have the maps/surveys etc. to make this relative straight forward.
Whatever ends up being the solution to these problems we need to make government act. Historically the best way to do that has been non violent direct action. As we are at crisis point now (5yrs until the arctic has melted based on current melt) it is really our final option. You may be interested in joining the Extinction Rebellion to make this happen.
My interest grew from this: https://www.youtube.com/watch?v=vpTHi7O66pI But this video has a lot more detail: https://www.youtube.com/watch?v=q7pI7IYaJLI Why growing trees in the sahara won't work: https://www.youtube.com/watch?v=lfo8XHGFAIQ And this is long but has a lot of detail about holistically managing livestock and the effect on soil structure etc. https://www.youtube.com/watch?v=8HmoAIykljk Finally the Extinction Rebellion - https://extinctionrebellion.org