We don't need those grazing lands for growing food (some nuts forests would be cool, though). We should afforest/rewild it to store maximum carbon in those lands, repair water cycle, enable biodiversity to return (70% of species is lost in the last 50 years or so), and use land for animal feed crops to feed humans instead.

If we'd switch to plant based diets, we'd free an area the size of Africa to return back to nature, storing enough carbon to return to 280ppm, stop biodiversity loss, while feeding comfortably 10+ billion people.

https://ourworldindata.org/land-use-diets

If the world adopted a plant-based diet we would reduce global agricultural land use from 4 to 1 billion hectares

https://pubmed.ncbi.nlm.nih.gov/26231772/

Biodiversity conservation: The key is reducing meat consumption

https://www.eurekalert.org/news-releases/917471

Feeding 10 billion people by 2050 within planetary limits may be achievable

A global shift towards healthy and more plant-based diets, halving food loss and waste, and improving farming practices and technologies are required to feed 10 billion people sustainably by 2050, a new study finds.