Their horses, which included many spotted individuals, were prized and envied by other tribes. Cattle ranchers believed that wild horses competed with cattle for grazing land and were often blamed for the destruction of the land that was the fault of the overgrazing caused by cattle. At the beginning of 1800, over 60 million buffalo grazed the Great Plains along with large numbers of wild horses, so it is hard to imagine that horses were responsible for the large scale erosion of grasslands. In fact horses play an important role in the regrowth of new grass. Horses don't fully digest their food as cows do.
Horses pass seeds through their system that are deposited in their droppings.
Fires often occurred on the plains and the seeds deposited in horse droppings were insulated from the heat of the fires and would sprout into new growth. Cows chew cud which fully digests the seed, destroying it. Today, Western herds total more than 39,000 horses, with most of the animals in Nevada. There has been considerable controversy over the management of these herds which carries over into today. These horses are called 'Brumbies' after a British soldier, James Brumby, who may have been responsible for abandoning the first horses in the early 1800's.