The easterners then brought in domestic cattle, an invasive species not found naturally on the North American continent, and today there are more than 120,000,000 of these invaders grazing the plains that once fed 60,000,000 bison.
Cattle are intensely destructive of land, even when their numbers are within what the land can support. Bison have a migratory instinct that keeps them moving every few days, so they do not overgraze an area. Cattle lack this instinct, so if you drive them into a meadow in the spring, you can go away and come back in the fall, and they will still be there. But the meadow won't.
When bison come to a stream to drink, they spread out, so the damage to the streambank is minimal. When cattle come to a stream, they bunch up, resulting in erosion, a lot of damage to streambank vegetation and silt in the water that chokes fish.
Bison can protect themselves from American predators such as wolves, bears, and mountain lions, but cattle have to be protected by a government agency called Wildlife Services, that systematically leaves poison all over the west to kill anything that eats meat, including animals like badgers, coyotes, foxes, hawks, owls, and other animals too small to threaten a cow.
Bison are immune to diseases that cattle are not, so the meat you buy is laced with antibiotics, a health hazard the US forces the European Union to import despite their consumer protection laws against it in beef raised in Europe.
Bison can dig down through snow in winter for food, but cattle have to have it dropped to them by helicopter, raising the price of beef considerably.
Every winter, 10,000 elk and antelope are killed by barbed wire fences set up to control cattle blocking their migratory routes.
Bison meat is healthier for the consumer. It has more protein and less fat and cholesterol than beef, and since they are larger animals, 60,000,000 bison would provide as much meat as 120,000,000 cows.
In short, the cattle industry is incredibly destructive. And there is no need for it. In fact, it is not economically self-supporting. The cost of grazing permits on publicly owned rangeland is kept artificially low by political influence and is only around 1% of the cost of grazing on comparable privately owned rangeland, so 99% of the cost of grazing those cattle is a subsidy from the taxpàyer to the cattle ranchers. By every measure, from health, to cost of meat, to protecting wildlife, to protecting the land from over-grazing, to saving public funds, the most productive use of the Great Plains would be to abolish cattle ranching and allow the bison herds to recover, remove the barbed wire fences and allow them to migrate freely, and then issue hunting permits.
It has been suggested to use cloudbusters to end the drought in the American Southwest. That probably should be done at some point, but not until the cattle ranchers have been driven into bankruptcy and forced to abandon their destructive industry for some other means of making a living. I see the drought as an oportunity, not a disaster, a chance to force the cattle ranchers out of business. After that has been done, it would be time to use cloudbusters to end the drought.
The drought is bad, but cattle ranching is worse. Droughts come and go. The cattle industry keeps right on trashing the West, year after year. They are both disasters; to end a drought to save cattle ranchers from going broke and quitting the business and going away and doing something else for a living is counter-productive. The ideal outcome would be to let the drought to go on long enough to bankrupt the ranchers, and THEN end the drought.