Under current park restrictions, grazing and the keeping of livestock is now prohibited on park grounds. Being an arid climate, soil crusts are a vital process of replenishing nutrients and stabilizing soil. Complete regeneration of these crusts can take up to 4000 years depending on the dryness. Humans and livestock both disturb these crusts by crushing them as they traverse. The Spanish originally brought livestock over in the 1500s but it was not detrimental until the introduction of the railroad. Trains carried tens of thousands of livestock animals to the Colorado Plateau, likely at 2-3 times the sustainable stocking rate. The overgrazing of this period severely deteriorated range quality and halted regeneration of Ponderosa pines due to soil erosion. When Theodore Roosevelt made the Grand Canyon a game preserve, grazing was slowed but not stopped. The Taylor Grazing Act of 1934 slowed grazing rates even further, effectively controlling overgrazing by this time. The patchwork ownership of the Plateau today makes management difficult. Currently, the Grand Canyon Trust is attempting to buy ranching claims to retire them permanently. Also worth noting is when a predator control program was put in place in the park. Many predators like wolves or mountain lions were eradicated in the park. Native grazing populations soared and caused direct competition with livestock. There was just not enough food to go around. Charles “Buffalo” Jones attempted to bring buffalo into the canyon as a stronger form of cattle but ultimately failed. Buffalo have entered the park on their own, however. Within park boundaries, they cannot be shot, and with this in mind, they have naturally began to encroach on the park. Buffalo are not native to the area and burn through vegetation incredibly fast. They also soil the water holes they visit. The Grand Canyon in general has seen a degradation in the quality of plant life ever since livestock was introduced by human intervention.