Short answers, pulled from the story.
Grazing occupies 26 percent of Earth's terrestrial surface, according to the Food and Agriculture Organization. About 60 percent of the world's grassland, which is just less than half of the world's usable surface, is covered by grazing systems.
Sheep were domesticated first, followed closely by goats; both species were suitable for nomadic peoples before fixed settlements existed. Cattle and pigs were domesticated somewhat later, around 7000 BC, once people began living in permanent locations.
Patch-burn grazing burns a third of a pasture each year, attracting cattle or bison to graze the fresh regrowth heavily while the other patches rest. The Tallgrass Prairie Preserve in northeastern Oklahoma has used this method with bison herds for over ten years, restoring the bison-fire relationship across 30,000 acres.
The Taylor Grazing Act of 1934 was a United States law enacted after the Great Depression to regulate the use of public land for grazing purposes. Livestock had been grazed on American public land since the Civil War before this regulation was put in place.
A 2013 FAO report estimated livestock were responsible for 14.5 percent of anthropogenic greenhouse gas emissions. Research published in the Journal of Animal Science found that grass-fed cattle produce four times as much methane as grain-fed cattle, due to their high-fiber, low-quality diet.
An estimated 100 million people in arid areas rely on grazing livestock as their only possible source of livelihood, with a similar number likely dependent in other zones, according to the Food and Agriculture Organization.