I think we're mixing a lot of different things there and moving from one thing to the next.

I like decomposing things. Not in the poop rotting sense but in the divide and conquer sense.

    1. Wet pasture with too many animals can destroy the pasture.

Sure. Put less animals. Also, make better pasture, i.e. pasture that is not grazed down to 1/4" with almost no protective function of the grass/roots. Move the animals well before it reaches that level and you prevents dustbowls in different ways. One of them being that the sun can't actually reach the soil. You basically never want sun touching bare soil on your pasture.

    2. Shelter

Now this is very true. And it's bad for the animals if they have no shelter. They heat up beyond levels that are healthy for them and they will use more water, which both increases your water needs as well as your labour needs to get water to them. Or resource inputs to lay pipe to get the water to them, which requires maintenance etc. I guess you get the point / know already. So yes, divide the huge fields into smaller fields that are lined with trees that the animals can naturally gravitate towards when needed.

    3. Poop as fuel

The poop as fuel is collected wherever it happens to turn up. Which in said parts of Africa can be on a large dustbowl.

    4. Not enough earths

I think this is overstated sometimes. Yes, if we use the US farming practices it's probably true. There are alternatives. Unfortunately I don't know the name. I saw this documentary on a flight quite a while ago.

Basically many of these parts of Africa that can't feed themselves were able to do so just fine before the westeners arrived and removed all the trees and made fields out of everything. Now it's barren earth. There was that one guy who - over lots of years and twists and turns I don't remember exactly any more - who figured out that the trees they bulldozed are not actually gone. The root system is still there. Below the surface and if you protect the tiny branches that appear from time to time from animals these grow back into beautiful trees that create shade for people, animals and further growth. He basically went around the villages, talking to elders that still remember the old times, making them his allies to teach children and younger adults to care for the tiny trees and to nurture them back to full growth / life. That was quite a while ago and it works. Many many villages can now feed themselves again.

All that to say: they basically went from a situation where even 10 "earths" worth of the situation they had would not have sufficed, a single earth worth of properly managed trees and ecosystem is perfectly capable of feeding them.